To play the Science Adventure Challenge, choose a level of difficulty from the buttons to the right. A question will be displayed in this window. Then begin searching for the screen that answers the question. Every time you use the globe, the timeline, or any other method of interaction with Science Adventure, your score will increase.
It will keep increasing until you get to the screen that answers the question. Try to keep your score as low as possible.
If you need help, return to this screen and select the Hint button. This will cost you some points, though!
When you land on the right screen, Science Adventure will let you know!
╢ Using Science Adventure
If you need help using Science Adventure, read the following information. When necessary, click on the down button at the bottom of this text box to continue reading. KEYBOARD USERS: Move the cursor to a down button using the arrow keys or tab key, then press Enter. Tab and Shift-Tab move the cursor to various clickable areas.
PICTURE WINDOW
By clicking on elements in the picture window, you can travel to a time and place somehow related to the object you click on. If nothing happens, try clicking elsewhere in the picture.
TEXT WINDOW
You are now using the text window. Move forward or backward in the window by using the up and down arrow buttons below.
By clicking on a word in the text window, you can access the index to find other references to that word in other screens.
TIMELINE
The timeline below the picture window changes to reflect the date of the current screen. To travel to a specific time in history, click anywhere on the timeline. To move forward or backward one screen at a time, click once on the right or left arrowheads at either end of the timeline. You can also pick up the slider by holding down the mouse button and dragging it to any other time in history. KEYBOARD USERS: Press the Plus key to move forward in time or the Minus key to move back in time.
GLOBE WINDOW
Click on any point in the globe window (in the upper left of the screen) to travel to the nearest point geographically. Move closer to or further from the earth using the slider bar. You can click anywhere on the slider or on the arrowheads at either end of the slider. You can also pick up the slider by holding down the mouse button and dragging it. KEYBOARD USERS: Press Ctl-PgDn to move closer to the earth and Ctl-PgUp to move further from the earth.
You can rotate the globe using the four arrow buttons below the window. Or, you can rotate it by holding down the mouse button at any point on the globe. KEYBOARD USERS: Hold down Ctl and press the up, down, left, or right arrow keys.
To see the globe in full-screen size, press the expand button just below the globe slider. To return the globe to normal size, press the expand button again.
CATEGORY BUTTONS
The seven upper-row buttons are category buttons. From the left, they are: Mathematics, Physics, Chemistry, Biology, Technology, Earth-Ecology, Space.
You can move sequentially through the history of a category by clicking repeatedly on a category button. Or, you can lock in one or more categories (or unlock them) by holding down the shift key and clicking on them. When a category is locked in, a yellow box appears around the button and your travels using the globe and timeline will be limited to that category, or categories.
FUNCTION BUTTONS
Function buttons are the seven buttons just below the category buttons. They are Help, Retrace, Game, Zoom, Sound, Print and Library. Help takes you to this screen. Retrace takes you to the previous screen. Game lets you take a quiz to test your science knowledge. Zoom shows you a full-screen picture. Sound plays a sound associated with the picture. Print prints the contents of the text window. Library lets you look up information alphabetically and lets you quit Science Adventure.
b Exit - Salida - Sortie
If you really want to quit your current adventure press Quit, otherwise press Continue.
ZThe First Calculator
500 BC
CAIRO, EGYPT
No one knows when the abacus first came into use, but it was probably known in Egypt at least as long ago as 500 B.C.
It consists essentially of rows of beads, sometimes strung on wires. In the simplest form there are ten beads on each wire, the first row being units, the second row being tens, the third row being hundreds and so on.
The beads can be manipulated much as we manipulate the fingers on a hand in simple adding and subtracting. The advantage is that you may have nine or ten "hands" present as so many rows of beads, and the movements you make are easier and quicker than manipulating your fingers would be.
A skilled operator can use the abacus flashingly to multiply, to divide, and to perform many complicated arithmetical manipulations. It was the first really important computing device worked out by human beings.
[Africa: Troubled Continent
1990 AD
AFRICA
If you always thought of Africa as mostly jungle, you can see from this satellite's-eye view that it isn't so.
In fact four-fifths of the world's second largest continent is made up of desert and grasslands. Less than a fifth is forest, and because of people's encroachment on the forest, it is unfortunately less forested every day.
Africa is made up of more than 11 million square miles, or 17.9 percent of the earth's land surface. With about 661 million people, it is second in terms of population, but far behind Asia's total of 3.1 billion people.
At the north edge of Africa you can see the vast Sahara, the largest desert in the world, covering about two-fifths of the continent.
The Sahara so divides the continent that people often speak of North Africa and Sub-Saharan Africa as if they were not connected. And indeed, they are very different.
The northern Mediterranean coastal area is largely Muslim and inhabited by Arabic peoples, while the vast southern portion of the continent is inhabited by black peoples who are largely Christian or animistic.
Africa is home to Egypt, one of the world's most ancient civilizations, estimated to be about 5,000 years old. And though not as much is known about them, great civilizations have also flourished in Sub-Saharan Africa.
The first of these civilizations, Timbuktu (a great university city), Goa and Ghana, arose along the southwestern edge of the Sahara as trade across the desert developed.
Ghana appears to have been founded about 300 AD and reached its height about 1,000 AD, when the empire of Mali arose to conquer it.
In the 1500s the Songhai Empire rose, spreading from the Atlantic to what is now central Nigeria. And Kanem-Bornu, around Lake Chad (the small spot just above the dark green section near the middle of the continent) was founded in the 700s and lasted a thousand years. It was known for its fierce iron-mailed knights.
Later, other civilizations arose further south. Kongo arose around the mouth of the Congo River and Zimbabwe became a great empire in south eastern Africa.
The isolated mountain nation of Ethiopia has a separate history. It traces its civilization to the Bible story of the Queen of Sheba's visit to King Solomon of Israel. According to the Ethiopian story, Solomon and the queen had a son named Menelik, who founded Ethiopia. Among the treasures of this country are beautiful churches in the town of Lalibela that have been carved in single pieces out of bedrock.
One of the most shameful periods of African history began in the 1400s when the Portuguese established trading posts on the west coast and began buying slaves. The slaves were generally prisoners taken in inter-tribal warfare who were sold to Europeans or Arabs.
The trading led to European political involvement, and during the 1800s Europe took over much of Africa, excluding only Ethiopia and Liberia, a colony founded by freed American slaves.
Naturally, that period is regarded as humiliating by Africans, though it did bring medicine and education to the area. And, interestingly, many of those who led independence movements were products of European schooling.
Currently, Africa is one of the most troubled areas of the world, facing poverty, disease, warfare and environmental decline.
In South Africa, for example, there are divisions between whites and blacks and between blacks and blacks. Much of the tribal violence throughout Africa was caused by how colonial governments divided the continent, often paying little attention to ethnic boundaries.
But perhaps the most badly afflicted area is in the northeast. Ethiopia, Somalia and Sudan have all been victims of periodic famines combined with government mismanagement and warfare.
Also afflicting Africa is the decline in its famous jungle areas and in its wildlife, caused primarily by over-hunting and by people taking over the animals' habitats.
~One Plague Goes, Another Comes
1977 AD
SOMALIA, EAST AFRICA
In 1977 the last case of smallpox was recorded, in Somalia. The smallpox virus is now thought to be extinct except for samples grown in laboratories for research purposes.
The ending of one scourge, however, seemed to have been balanced by the coming of another. In 1977 two male homosexuals in New York City were found to have a rare form of cancer, which was eventually recognized to be a symptom of a disease called acquired immune deficiency syndrome, usually abbreviated AIDS. This disease, usually fatal and so far incurable, spread rapidly and became as feared in the 1980s as smallpox was in the 1780s.
»An Alphabet for Math
1591 AD
PARIS, FRANCE
Until now, mathematicians had described quantities, relationships, and problems in words (it seemed the only way), and what they described was often hard to envisage.
Francois Vieta (1540-1603) began to symbolize constants and unknowns by letters of the alphabet, the now familiar x's and y's of algebra. In 1591, he wrote a book about algebra that was the first a present-day high-school student would recognize at a glance to be dealing with that subject.
The progression from words to symbols was to mathematics something like the progression from ideographs to letters in ordinary writing, or from Roman numerals to Arabic numerals in arithmetical computation.
!A Better Way to Carry Water
9000 BC
MESOPOTAMIA
It has always been important for human beings to carry things, and the obvious way to carry them is in the hands, or in the crook of the arm. There is a limit to how much can be carried in this fashion, however. What we needed were artificial hands, so to speak, that were considerably larger than our natural hands.
Objects could be carried in hides, but hides are an inconvenient shape and heavy. Gourds might do, but they have to be taken as they come. Eventually human beings learned to weave twigs or other fibers into baskets. These were light and could be made in any shape.
Baskets, however, were only useful in carrying solid, dry objects made up of particles considerably larger than the interstices of the weave. Baskets could not be used to carry flour or olive oil, for instance, or most important, water. It might seem natural to daub baskets with clay, which upon drying would cake the holes and make the basket solid. The dried mud would tend to fall away, however, especially if the basket was shaken or struck. But if the basket was placed in the sun and allowed to bake in direct sunlight, the mud would harden further, and the basket might then become fairly serviceable for carrying powders and fluids.
But then why use the basket? Why not simply begin with clay, mold a container out of it, and let it dry in the sun? You would then have a pot made of crude earthenware, and some of these may have been formed as early as 9000 B.C. Such pots are soft, however, and don't last long.
Some stronger heat was required. When earthenware was placed in the fire, it became hard pottery, and such pottery can be traced back to perhaps 7000 B.C. This may have been the first use of fire for something other than light, heat, and cooking.
Pottery not only made it possible to carry liquids, it also introduced a new form of cooking. Until then, food had usually been roasted, exposed directly to the flames or to dry heat. Once a pot existed that could hold water and withstand the heat of flames, food could be heated in the water -- it could be boiled. In this way stews and casseroles came into existence. And of course pottery could be decorated and well shaped. Cleverly decorated examples would be in special demand. Artisans could exchange them for other material they found needful. And since pottery lasts indefinitely, if well cared for, it can change hands often, and one group of people can use it in trading with another group.
In early pottery, the clay was pressed and pounded into the shape of a pot and the result was something quite lumpy and asymmetric but serviceable. If the pot could be turned, however, a relatively light pressure from the hand would produce a symmetrical cylindrical shape, and by appropriate increases in pressure or by downward pushes, complicated modifications of the basic cylinder could be made while retaining symmetry. This could be done if the clay was placed on a horizontal, circular slab of wood or stone (a potter's wheel), which had a central spike underneath that could be balanced in a depression and the whole turned rapidly.
The potter's wheel was one of the first examples of the use of a wheel and one of the first uses of rotary motion. We don't know when it was first used, but it may have led to the idea of wheel generally, and to wheeled transportation.
¿Round and Round: Spiral Nebulas
1845 AD
DUBLIN, IRELAND
The nebulas that had been seen in the sky until 1827 had seemed to be no more than little cloudy patches. Telescopes weren't good enough to make out much in the way of structure -- or perhaps structure was simply lacking in them.
In 1827, however, an Irish astronomer, William Parsons, Earl of Rosse (1800-1867), began work on the largest telescope yet planned, and by 1845 it was finished. It had a mirror that was 72 inches across. However, the telescope, though large, was clumsy. It couldn't see much of the sky even when the sky was clear -- and it was hardly ever clear.
Nevertheless, the telescope did accomplish a few things. In 1845 Rosse noted that one nebula had a distinct spiral shape, and in the following years he found fourteen others that were also spiral in appearance. These were termed spiral nebulas, and the time was to come, eighty years later, when they achieved considerable importance.
ÆPainless Surgery
1846 AD
MASSACHUSETTS
Pain, however useful as a warning signal designed to keep living organisms from damaging themselves too badly, becomes useless agony when operations must be performed.
Attempts to control pain were many. The use of alcohol or some form of what came to be called hypnotism was old. Acupuncture was used in the Orient. The new chemistry also contributed nitrous oxide, which, when inhaled, served to suppress the sensation of pain.
As time went on, substances such as di-ethyl ether (more commonly called simply ether) and chloroform were found to cause unconsciousness during which the sensation of pain disappeared. Ether came to be used by physicians during operations, the first to do so being an American physician, Crawford Williamson Long (1815-1878), who used it in 1842 to remove a tumor. He did not publish or publicize his work, however.
An American dentist, William Thomas Green Morton (1819-1868), used ether on a patient in September 1846, when extracting a tooth. The patient himself told the tale to a newspaper, and Morton was urged to demonstrate the use of ether during an operation at Massachusetts General Hospital.
It was this demonstration that effectively introduced the practice into medicine, so that Morton usually gets credit for the discovery. The American physician Oliver Wendell Holmes (1809-1894) suggested the term anesthesia, from Greek words meaning "no sensation."
₧Tuning in to Hydrogen
1951 AD
CAMBRIDGE, MASSACHUSETTS
Dutch astronomer Hendrik Christoffel Van de Hulst (b. 1918) had predicted in 1944, from theoretical considerations, that hydrogen atoms in space would emit microwave radiation with a wavelength of 21 centimeters.
In 1951 American physicist Edward Mills Purcell (b. 1912), who had earlier helped work out the theory of nuclear magnetic resonance, actually detected this radiation coming from outer space. This demonstrated the value of radio waves in detecting the presence of given atoms and molecules in interstellar space. The wavelengths of the radiation emitted were characteristic of different substances and acted as "fingerprints."
KA Continent Hidden by Ice
1839 AD
ANTARCTICA
The American explorer Charles Wilkes (1798-1877) commanded an exploring expedition in Antarctic waters between 1838 and 1840. He cruised along the limits of the sea to the south of the Indian Ocean. Ice everywhere prevented him from landing, but he saw enough land at a distance to realize, by 1839, that there was a continent within the Antarctic Circle. The information he brought home demonstrated this amply (and part of the Indian Ocean sector of the continent is still called Wilkes Land in his honor), so that Wilkes may be considered the discoverer of Antarctica.
ΓThey Kill Lots of Germs
1948 AD
UNITED STATES
In 1948 a new antibiotic, chlortetracycline, discovered four years earlier by the American botanist Benjamin Minge Duggar (1872-1956), was placed on the market as Aureomycin. Its molecule was made up of four rings of atoms, and it was the first of a family of such antibiotics with the general name of tetracyclines. They were effective over a wide range of microorganisms and had low toxicity. They are now the most useful and least dangerous of the antibiotics.
5Protein Structure
1969 AD
UNIVERSITY OF CALIFORNIA, BERKELEY
The techniques for elucidating protein structure had continued to advance since British biochemist Frederick Sanger's (b. 1918) work on the structure of insulin.
In 1969 the American biochemist Gerald Maurice Edelman (b. 1929) worked out the structure of a gamma globulin, a type of protein that exists in the blood and out of which various antibodies are formed. (Antibodies react with particular foreign proteins, so that they are essential to the body's immune mechanism.) For this, Edelman received a share of the Nobel Prize for physiology and medicine in 1972.
Also in 1969, British physicist Dorothy Crowfoot Hodgkin completed our knowledge of the insulin molecule by working out its three-dimensional structure.
And still in 1969, the Chinese-born American biochemist Choh Hao Li (b. 1913) synthesized the enzyme ribonuclease, putting every one of its 124 amino acids into a chain in the right order. Ribonuclease, which catalyzes ribonucleic acid's breakdown into smaller fragments, was the first enzyme to be synthesized.
Sagittarius Calling!
1932 AD
PRINCETON, NEW JERSEY
As radio came more prominently into use for communication and home entertainment, the problem of static (a crackling interference that made communication uncertain and music unpleasant) cried out for correction. Static had a number of causes, including thunderstorms, nearby electric equipment, and aircraft passing overhead.
The Bell Telephone Company, which needed radio for ship-to-shore calls, among other things, set one of its employees, Karl Guthe Jansky (1905-1950), to exploring the problem.
Jansky detected a new kind of weak static from a source that at first he could not identify. It came from overhead and moved steadily. At first it seemed to Jansky that it must be the Sun. However, the source gained slightly on the Sun to the extent of 4 minutes a day. This is just the amount by which the vault of the stars gains on the Sun, so that the source must lie beyond the Solar System.
By the spring of 1932, Jansky had decided that the source was in the constellation of Sagittarius, the direction in which American astronomer Harlow Shapley had placed the center of our galaxy in 1918.
This represented the birth of radio astronomy, in which astronomers learned to receive and interpret radio waves rather than light waves. Light waves, of course, are easily perceived by the retina of the eye and by photographic film. In 1932, however, perceiving radio waves with any precision was extremely difficult, for instruments were lacking. Therefore, the development of radio astronomy was delayed for some twenty years.
²Water for Thirsty Cities
700 BC
NINEVEH
As cities grew, supplying what was needed to so many people so densely packed together became a problem. Air itself, the most immediate and pressing necessity, was available everywhere more or less (though the use of fires in every house could fill that air with unpleasant smoke).
Water was more of a problem. Cities are usually built where there is a water supply, but as they grow, the water supply may become insufficient. Wells within the city limits or just outside may not supply enough. It may then become necessary to fetch water from some distance, either through canals or tunnels or along artificial structures of masonry.
These last are called aqueducts (from Latin words meaning "a drawing off of water") and by 700 B.C., Sennacherib, who was king of Assyria from 704 to 681 B.C., had an aqueduct constructed that would bring water into his capital, Nineveh. At about the same time, Hezekiah, king of Judah from about 715 to about 686 B.C., built an aqueduct to supply Jerusalem with water.
Easier Than IV Plus LXI
1202 AD
PISA, ITALY
An Italian mathematician, Leonardo Fibonacci (ca. 1170-after 1240), had occasion to travel widely in North Africa, since his father was a merchant. There he learned of Arabic numerals and positional notation, which had been advocated by Arabic mathematician Muhammad ibn Al-Khwarizmi (780-850).
Fibonacci wrote a book on the subject in 1202, Liber Abaci (Book of the Abacus). This served to introduce Arabic numerals to Europe, but Roman numerals held their own for three more centuries before succumbing.
Arches: United We Stand
750 BC
ROME, ITALY
The easiest way to build an opening is to set up two vertical pieces of wood, stone, or other material and then balance a horizontal piece above the two.
The horizontal piece, unsupported in the middle, can break with relative ease, and the weakness increases as it grows longer. If instead one uses relatively small pieces arranged in a vertical semicircle so that each piece helps support the piece above, and if one uses mortar to make the pieces adhere to each other, one has an arch.
An arch can span a much wider distance and carry a much heavier load than a horizontal piece can.
Small, primitive arches were used as early as Sumerian times, but a true arch, properly built for maximum strength, showed up for the first time among the Etruscans in 750 B.C.
Θ The Bubble That Stayed
1894 AD
GREAT BRITAIN
Ever since English chemist William Prout (1785-1850) had suggested that all atoms were built up of hydrogen atoms, chemists had been checking the atomic weights of various elements with greater and greater accuracy. The fact that so many atomic weights were not multiples of hydrogen's seemed to disprove Prout's hypothesis.
Twelve years before, for instance, the British physicist John William Strutt, Lord Rayleigh (1842-1919), had shown that the atomic weight of oxygen, although usually considered to be 16 times the atomic weight of hydrogen, is actually 15.882 times the atomic weight of hydrogen.
Rayleigh went on to measure the atomic weight of nitrogen and then encountered a puzzle. Whereas oxygen always had the same atomic weight no matter how it was prepared, nitrogen did not. Nitrogen prepared from the atmosphere consistently showed a slightly higher atomic weight than nitrogen prepared from a variety of nitrogen-containing compounds.
Rayleigh could not find a suitable explanation for this and wrote a letter to the journal Nature, asking for suggestions. The British chemist William Ramsay (1852-1916) rose to the challenge. He remembered having read that British chemist Henry Cavendish (1731-1810) had tried to combine the nitrogen of air with oxygen and had found that a small bubble of gas remained behind, which would simply not combine with oxygen. Cavendish had thought there might be some small quantity of gas in the atmosphere that was more dense than nitrogen, and more inert, too, but had not pursued the matter.
Ramsay repeated the experiment, and he too found himself with a small bubble of gas left over. He had spectroscopic techniques, however, which Cavendish had not had. Ramsay heated the bubble of gas, studied the spectral lines it emitted, and found them to be in positions that fitted no known element.
Clearly here was a hitherto-unknown gaseous element, which made up about 1 percent of the atmosphere. It was completely inert and would not react with any substance. It was also denser than nitrogen. The presence of this new gas as an impurity in the nitrogen obtained from air gave the nitrogen an abnormally high atomic weight, whereas nitrogen obtained from chemicals without any admixture of this impurity gave the true atomic weight.
The discovery was announced on August 13, 1894, and the new gas was named argon, from the Greek word for "inert." As a result, Rayleigh received the Nobel Prize in physics and Ramsay the Nobel Prize in chemistry in 1904.
\Simplifying Radio
1916 AD
NEW YORK, NEW YORK
Until now, radio operation had been a rather complicated thing that had to be left to radio engineers. In 1916, however, the American radio engineer Edwin Howard Armstrong (1890-1954) worked out a system for lowering the frequency of electromagnetic waves and then amplifying them. He called this a superheterodyne receiver.
çAsia: Most Populous Continent
1990 AD
Roughly defined, Asia stretches from the Ural Mountains in Russia in the west to Japan and the Pacific Ocean in the east and from the Arctic Sea south to India and Indonesia.
Like a wide belt across the length of Asia is the vast steppe, a swath of grassland that stretches from east to west. Though almost devoid of people compared to the densely populated southlands of the continent, the steppe has been important in the history of the world. From it have burst such conquerors as the Huns and Mongols, who ravaged both China and Europe.
The southern half of the continent is much more broken up geographically, and thus, culturally as well. The vast Himalayan mountain range, which boasts the tallest mountain in the world, Mt. Everest, has to a great degree isolated Tibet, India and Burma from China and Central Asia. In the far east, wide stretches of water separate Japan, the Philippines and Indonesia from the rest of Asia.
Despite these obstacles, China and India in particular have been extremely important in the history of Asia.
Just as civilization developed around the Nile River and around the Tigris and Euphrates rivers in the Middle East, so it happened in the East. In China people settled around the Yellow River and in India around the Indus River.
In a succession of dynasties and warring kingdoms, China expanded to the south and west and developed a culture advanced in technology, art, literature and philosophy.
India is important as the birthplace of Hinduism and more importantly, of Buddhism, which has spread throughout Asia.
Today, Asia is the most populous continent in the world, with more than three billion people.
╨Ford's Way of Working
1908 AD
DETROIT, MICHIGAN
During the first twenty years of its existence, the automobile had been improved greatly and manufactured in greater numbers. It remained very largely a toy of the rich, however, rather as yachts are today.
The man who changed that was the American industrialist Henry Ford (1863-1947). He had built his first automobile in 1893 and started a car- manufacturing company in 1899. His aim was to produce cars in quantity (mass production) and to make them cheaply enough to put them within reach of middle-class Americans.
His key innovation came in 1908, when he thought of dividing the manufacture of cars into steps, each of which could be performed simply by a single worker. He then placed the future car on a moving belt that brought it to different workers in succession, each of whom performed the assigned task over and over, with all necessary tools and parts within reach. What started at one end of the assembly line was a mere skeleton of a car. What rolled off the other end was a complete, functioning automobile, including a gasoline supply so that it could be driven away.
Ford produced a series of models identified by letters of the alphabet and finally considered the Model T suitable for mass-production. It cost only $950 to begin with, but the price dropped in succeeding years, eventually reaching a low of $290. For the first time, the average man could afford to buy a car, and the automobile age -- still in full swing today -- began.
½Earth at the Center?
140 AD
ALEXANDRIA, EGYPT
Claudius Ptolemaeus (2d century), better known as Ptolemy, was the last important astronomer of the ancient world. He wrote a summary of ancient astronomy, known later to the Arabs as Almagest (the greatest). He drew largely from Hipparchus.
In this synthesis, he described the Earth as the center of the Universe and all the planets as going around it in combinations of circular motions. In order to account for the visible motions of the planets across the skies, those combinations of circular motions had to be complicated indeed, but Ptolemy worked out mathematical methods for predicting planetary motions that seemed adequate to his contemporaries and to future generations for fourteen centuries. (His chief instrument was an astrolabe, a device for determining the latitude of the heavenly bodies. It had been invented a couple of centuries before and is considered the oldest of scientific instruments.)
▒Keeping Time with Molecules
1949 AD
US NAVAL OBSERVATORY, WASH DC
Ever since Dutch astronomer Christiaan Huygens (1629-1695) had invented the pendulum clock in 1656, scientists had depended on accurate time measurements in conducting their experiments and searched always for more and more accurate ways of measuring time.
Eventually the search for natural cyclic movements that were both precise and constant worked down to the molecular level. An ammonia molecule, for instance, vibrated back and forth, taking up its two possible tetrahedral positions alternately, about 24,000,000,000 times per second. At constant temperature, this vibration remained very constant.
In 1949 the American physicist Harold Lyons (b. 1913) was the first to harness this molecular vibration to time-keeping purposes. It was the first atomic clock. As atomic clocks of ever-greater precision were devised, physicists could eventually time events to a millionth of a trillionth of a second.
Two Electron Orbits
1915 AD
MUNICH, GERMANY
The quantized atom of Danish physicist Niels Henrik David Bohr (1885-1962) did not explain all the fine details of spectra. Some dark lines that seemed simple, on closer investigation proved to consist of groups of narrow, closely spaced lines.
The German physicist Arnold Johannes Wilhelm Sommerfeld (1868-1951) felt the answer lay in the fact that electron orbits were more complicated than Bohr had suggested. Bohr had made use of perfectly circular orbits, but the orbits (like planetary orbits) might also be elliptical.
Sommerfeld used Albert Einstein's (1879-1955) theory of relativity to calculate the elliptical orbits and quantum theory to show that only certain kinds of ellipses were possible. The combination of circular and elliptical orbits explained some of the details of the spectra that Bohr's original treatment had left unexplained.
For this reason, people sometimes speak of the Bohr-Sommerfeld atom. It made use of the two great physical theories of the twentieth century, relativity and quanta.
≥The H-Bomb: Into the Abyss
1952 AD
KWAJALEIN ATOLL, MARSHALL ISLANDS
The American effort to produce a nuclear fusion bomb (hydrogen bomb) was successful. Hydrogen-2 fused at a lower temperature than hydrogen-1, and hydrogen-3 fused at a lower temperature still. Hydrogen-2 was a rare isotope of hydrogen, but there was enough present in the Earth's oceans to last humanity for billions of years. Hydrogen-3 was radioactive and had to be formed through nuclear reactions if enough was to be obtained for use. It was planned to fuse a mixture of hydrogen-2 and hydrogen-3 in liquid form by exposure to the temperatures and pressures produced by a fission bomb.
Such a fusion bomb was tested on a coral atoll in the Pacific Ocean on November 1, 1952, wiping out the atoll. The blast yielded energy equivalent to 10,000,000 tons (10 megatons) of TNT -- five hundred times the 20-kiloton energy of the Hiroshima bomb.
Yet it did not give the United States security. Within a year, the Soviets had exploded a fusion bomb of their own. Both sides continually improved the efficiency and power of their fusion weapons, and Great Britain and China also acquired the technology. As Oppenheimer had foreseen in 1951, the world descended further into the abyss of fear, from which it has not yet emerged.
╢There's North and There's North
1881 AD
ARCTIC CANADA
Since the time of English physicist William Gilbert (1544-1603), it had been understood that the Earth must have a North Magnetic Pole and a South Magnetic Pole. The general (and rather natural) feeling was that the magnetic poles would be near, or perhaps exactly at, the rotational poles. However, the Arctic and Antarctic regions of Earth, cold and desolate as they were, could only be explored with great difficulty.
It was not until June 1, 1831, that the North Magnetic Pole was actually reached. The feat was accomplished by a Scottish explorer, James Clark Ross (1800-1862). He found his compass pointing straight down, on the western shore of Boothia Peninsula, at 70.85 degrees North Latitude and 96.77 degrees West Longitude. The pole was discovered only because it was 2,100 miles from the geographic North Pole and therefore relatively accessible. In fact, it was only a few hundred miles north of the Arctic Circle.
ñThe Continent Nation
1990 AD
Australia is the only continent in the world that is also a single country. It was originally inhabited by aboriginal peoples who are believed to have worked their way down the chain of islands that are now Indonesia to settle the continent.
Australia was later claimed by Great Britain, which initially operated parts of it as a penal colony for those convicted of crimes in England.
Australia is the most lightly populated continent in the world, with just 17 million people, or an average of 5.2 per square mile.
The highest point of this island continent is Mount Kosciusko, which rises 7,310 feet above sea level in New South Wales. The lowest point is Lake Eyre in South Australia, a point 52 feet below sea level.
New Zealand, the smaller islands to the right of the picture, were first inhabited by the Maori people, who lost the area to English
immigrants following the costly (for both sides) Maori Wars.
╥The Too-Early Computer
1822 AD
CAMBRIDGE, ENGLAND
French mathematician Blaise Pascal (1623-1662)and German mathematician Gottfried Wilhelm Leibniz (1646-1716) had constructed calculating machines, but these were equipped to do only the very simplest tasks.
About 1822 an English mathematician, Charles Babbage (1792-1871), began thinking of something much, much more ambitious. He wanted a machine that could be directed to work by means of punched cards as in a Jacquard loom, that could store partial answers in order to save them for additional operations to be performed upon them later, and that could print the results.
Everything he thought of could be done, but not by purely mechanical means, using the techniques of Babbage's time. He spent virtually the rest of his life trying to build the machine, his plans growing ever more grandiose.
Babbage had conceived the modern computer, but he didn't have the necessary electronic switches. These were not to be developed for another century.
NBacon Writes the Rules
1620 AD
ENGLAND
The English philosopher Francis Bacon (1561-1626) published Novum Organum (New Organon) in 1620. The reference is to Aristotle's Organon, in which the rules of logic were drawn up.
Bacon argued strenuously that deduction might do for mathematics but it would not do for science. The laws of science had to be induced; that is, established as generalizations drawn out of a vast mass of specific observation. Such experimental science had already been put into practice, but Bacon supplied the theoretical backing for it, describing what is today called the scientific method.
XBacteria on the Tip of a Pin
1676 AD
AMSTERDAM, NETHERLANDS
Microscopists had been looking at minute sections of ordinary living organisms for twenty years and more, but a Dutch microscopist, Antoni van Leeuwenhoek (1632-1723), now surpassed them all.
Whereas other microscopists used combinations of lenses, Leeuwenhoek used small single lenses, but he ground them to perfection, so that they could magnify up to 200 times. He ground a total of 419 lenses in his long lifetime, even though he was already over forty when he took up this hobby.
In 1676, studying pond water, he found it contained living organisms so small they could not be seen with the unaided eye. He called them animalcules, but we call them microorganisms. By whatever name, Leeuwenhoek had opened up an entirely new microscopic zoo to the astonished eyes of humanity. (In 1677 he detected spermatozoa in semen.)
?The Exploding Cosmic Egg
1927 AD
BELGIUM
Friedmann had developed the theoretical concept of an expanding universe, and in 1927 the Belgian astrophysicist Georges-Henri Lemaître (1894-1966) drew what seemed a natural conclusion.
If the Universe was expanding as time went forward, then if we imagined the situation reversed and looked back in time, we should see the Universe contracting. (It would be as though we had taken a film of the expanding Universe and were running it backward.)
If we looked forward, the Universe might well expand forever, but if we look backward, the contraction had to be limited. Eventually, at a point far enough back in time, all the matter of the Universe would be compressed into one relatively small body, which Lemaître called the cosmic egg.
This cosmic egg apparently exploded in what came to be called the big bang and started the expanding Universe that now exists. Of course, Lemaître could offer no scientific explanation of where the cosmic egg came from and just how its explosion led to the present Universe. Physicists have been trying to work that out ever since.
ºSalt Water Power
1800 AD
COMO, ITALY
Italian anatomist Luigi Galvani (1737-1798), noting that dead muscle twitched when touched simultaneously by two different metals, had decided that electricity was involved and that it originated in the muscle. The Italian physicist Alessandro Giuseppe Volta (1745-1827) thought the electricity originated in the metals.
He began to experiment with different metals in contact and was soon convinced that he was correct. In 1800 Volta constructed devices that would produce electricity continuously if it was drawn off as produced. This created an electric current, which turned out to be far more useful than the nonflowing electric charge of static electricity.
At first Volta used bowls of salt solution to produce the flow. The bowls were connected by means of arcs of metal dipping from one bowl to the next, one end of the arc being copper and the other being tin or zinc. Since any group of similar objects working as a unit may be called a battery, Volta's device was an electric battery -- the first in history.
Volta then made matters more compact and less watery by using small round plates of copper and zinc, plus disks of cardboard moistened in salt solution. Starting with copper at the bottom, the disks, reading upward, were copper, zinc, cardboard, copper, zinc, cardboard, and so on. If a wire was attached to the top and bottom of this battery, an electric current would flow when the circuit was closed.
ÆThe Reusable Spacecraft
1981 AD
CAPE CANAVERAL, FLORIDA
Until 1981, all space vessels had been one-time operations, not reusable. It was clear that space exploration could be made more feasible if it were made less expensive by creating reusable vessels.
For that reason, the space shuttle was designed. Its purpose was to go into orbit and then return to Earth. It was not in itself designed to make spaceflight cheap; it was an expensive vessel. However, it would help engineers work out the techniques for developing a future generation of such vessels that would be cheaper.
The first shuttle flight took place on April 12, 1981, which happened, by coincidence, to be the twentieth anniversary of the first spaceflight, by Soviet cosmonaut Yury Alekseyevich Gagarin (1934-1968). The shuttle left and returned safely. It was the first of over a score of such flights during the next four and a half years to be carried through safely.
╬Consequences of a Cloudy Day
1896 AD
FRANCE
The discovery of X rays by German physicist Wilhelm Conrad Röntgen (1845-1923) fascinated a French physicist, Antoine-Henri Becquerel (1852-1908), who had been working on fluorescent substances as his father had before him. He wondered if perhaps the radiation given off by fluorescent substances might include X rays.
A fluorescent substance both he and his father had been interested in was potassium uranyl sulfate. In February 1896 Becquerel wrapped photographic film in black paper and put it in sunlight with a crystal of potassium uranyl sulfate upon it. He reasoned that sunlight would make the crystal fluoresce, and any X rays it produced would penetrate the black paper (as ordinary light would not) and fog the photographic plate.
Sure enough the plate was fogged and Becquerel decided that fluorescence did produce X rays. But then came a series of cloudy days and Becquerel could not continue his experiments. He had a fresh plate neatly wrapped in the drawer with a crystal resting upon it, but there was no sunlight to expose it to. Finally, unable to bear doing nothing, he developed the film anyway, just to make sure that nothing happened in the absence of sunlight.
To his amazement, the film was strongly fogged. Whatever radiation was passing through the paper did not depend on either sunlight or fluorescence. For this discovery, Becquerel received a share of the Nobel Prize in physics in 1903 and rightly so, for it had enormous consequences.
¡Calling on Watson
1876 AD
BOSTON, MASSACHUSETTS
The telegraph, now over thirty years old, transmitted only signals. The British-born American inventor Alexander Graham Bell (1847-1922) wanted something better than that. He wanted to send actual speech over the wires, by turning sound waves into a fluctuating electric current that waxed and waned as the sound waves compressed and decompressed air. The electric current could then be reconverted into sound at the other end.
He finally invented a device capable of doing that and first made use of it accidentally. He had spilled battery acid on his pants and automatically cried out to his assistant, "Watson, please come here. I want you." Thomas Augustus Watson (1854-1934), at the other end of the circuit on another floor, heard the instrument speak and ran downstairs.
On March 7, 1876, Bell patented the telephone. Edison improved it almost at once by devising a mouthpiece that contained carbon powder. When the carbon powder was compressed, it carried more current than when not compressed. As the sound waves compressed and decompressed the carbon powder, the electric current waxed and waned.
The telephone utterly revolutionized human communication.
5Walking Faster With Wheels
1839 AD
COURTHILL, SCOTLAND
The first vehicle a modern would recognize as a bicycle was designed in 1839 by a British blacksmith, Kirkpatrick Macmillan. It had two wheels, of which the rear was slightly larger, and a seat between. It had pedals, which were so arranged as to turn the rear wheel. It was heavy and clumsy and underwent a number of fundamental changes before becoming the instrument of today, but it did work. For the first time, progress had been made in allowing humans to make use of their own muscles to travel at a speed greater than they could run.
Fighting Disease With Forty Days
1403 AD
VENICE, ITALY
Despite the fact that nothing was known about how disease came to be (except for theories of punishment by God or infestation by demons), people did tend to avoid those who were sick with some particularly fatal or loathsome disease.
Thus, leprosy (undoubtedly along with less drastic skin diseases) was treated as something that required isolation. Lepers were driven out of society. When the Black Death struck, people instinctively fled from those affected (sometimes leaving the dying to die and the dead to remain unburied).
In 1403 the city of Venice, always rationally ruled, decided that recurrences of the Black Death could best be averted by not allowing strangers to enter the city until a certain waiting period had passed. If by then they had not developed the disease and died, they could be considered not to have it and would be allowed to enter.
The waiting time was eventually standardized at forty days (perhaps because forty-day periods play an important role in the Bible). For that reason, the waiting period was called quarantine, from the French word for "forty."
In a society that knew no other way of fighting disease, quarantine was better than nothing. It was the first measure of public hygiene deliberately taken to fight disease.
u How the Blood Gets Around
1628 AD
NETHERLANDS
The idea of the Greek physician Galen (129-ca. 199) that the heart was a single pump and that there were pores in the thick muscular wall separating the right ventricle from the left ventricle was not universally accepted.
In 1242 an Arabic scholar, Ibn an-Nafis (d. 1288), wrote a book in which he suggested that the right and left ventricles were totally separate. Blood was pumped out of the right ventricle into arteries that led it to the lung. There, in the lungs, the arteries divided into smaller and smaller vessels, within which the blood picked up air from the lungs. The vessels were then collected into larger and larger vessels until they were brought back to the left ventricle from which the blood was pumped out to the body generally.
In this way, the double pump was explained. One pump was needed for the lungs and aeration; the other for the rest of the body. An-Nafis had grasped the lesser circulation. However, his book was not known to the West until 1924, and it had no effect on later developments.
In 1553 a Spanish physician, Miguel Serveto, known as Michael Servetus (1511-1553), published a book in which he too described the lesser circulation. The major part of the book, however, dealt with the Servetus's theological views, which were Unitarian. Servetus, having ventured into Geneva, which was ruled by his deadly enemy, John Calvin, was taken into custody and burned at the stake.
Calvin then attempted to destroy all copies of Servetus's book, and it wasn't till 1694 that some unburned copies were found.
In 1559 an Italian anatomist, Realdo Colombo (1516?-1559), became the third person to understand, independently, the lesser circulation. His work was the first to reach the medical profession, and it was much more detailed and careful than those of his two predecessors, so it is Colombo who gets credit for the discovery.
Then came the English physician William Harvey (1578-1657). He studied the heart carefully and noticed that each side had valves that allowed blood to enter each of the two ventricles but not to leave except by way of arteries. He also knew about the valves in the veins, since he had studied under Italian physician Girolamo Fabrici (1537-1619), who had discovered them. He experimented with animals, tying off a vein or an artery and noting that the blood piled up in a vein on the side away from the heart, but in an artery on the side toward the heart. It was clear to him that blood flowed away from the heart in arteries and back to the heart in veins.
By 1628, he had all the evidence he needed and he published a seventy-two- page book in the Netherlands with the title De Motu Cordis et Sanguinis (Concerning the Motions of the Heart and Blood). In it, he advanced his findings concerning the circulation of the blood: It leaves the right ventricle, goes to the lungs, and returns to the left ventricle. It then leaves the left ventricle, goes to the body generally, and returns to the right ventricle to begin all over.
The book was received sourly by the medical profession, but Harvey lived long enough to see it accepted. His book represents the beginning of modern physiology.
╕ Electrons' Energy Packets
1913 AD
DENMARK
Now that British physicist Ernest Rutherford (1871-1937) had formulated the nuclear atom, it was possible to view the hydrogen atom as consisting of a nucleus (bearing a charge of +1) and a single electron (with a charge of -1) circling it.
One could argue that the electron, as it circled the nucleus, in effect oscillated from side to side. This oscillation, according to Maxwell's equations, should result in electromagnetic radiation. But if this were so, the electron would lose energy as it circled and would spiral into the nucleus.
The Danish physicist Niels Henrik David Bohr (1885-1962) tried to solve this problem by applying quantum theory to the atom. The electron, he decided, could not radiate energy except in intact quanta, each of which represented a large amount of energy on the atomic scale. Consequently the electron, when it radiated, would lose a large packet of energy and would not spiral into the nucleus gradually but drop very suddenly to a lower orbit nearer the nucleus. It would do this each time it radiated a quantum of energy. Eventually it would reach the lowest orbital state, below which it couldn't fall, and it would then emit no more energy.
In reverse, if the atom absorbed energy, the electron would suddenly rise to a higher orbit, and this would continue with further absorption of energy until it left the atom altogether, at which time the atom would be ionized, becoming a fragment with a positive charge equal in size to the number of electrons that had been boiled off, so to speak. As electrons rose to higher orbits and fell to lower orbits, they would radiate only certain wavelengths, and under other conditions, absorb those same wavelengths, as German physicist Gustav Robert Kirchhoff (1824-1887) had shown over half a century before.
The presence of many electrons rising and falling in orbits might confuse the issue, but hydrogen, with its single electron, should be easier to handle. Indeed, hydrogen has a simple spectrum, giving off radiation at a series of wavelengths that can be related to each other by a rather simple equation. This equation had been worked out by a Swiss physicist, Johann Jakob Balmer (1825-1898), in 1885. It had not seemed to have much significance at the time, but now Bohr could choose orbits for a hydrogen electron that would yield just those wavelengths that the hydrogen spectrum displayed.
Bohr's suggestion wasn't perfect. There were fine details of the hydrogen spectrum that it couldn't account for. There was also no explanation of why the electron, when it was in a particular orbit and oscillating back and forth, did not lose energy. If it couldn't give off an entire quantum, why didn't it stop oscillating?
Bohr's suggestion, however, was the first application of quantum theory to the atom and was enormously important for that reason. The imperfections were gradually removed in succeeding years, and for his work, Bohr was awarded the Nobel Prize for physics in 1922.
+Gray Matters, Bumps Don't
1810 AD
VIENNA, AUSTRIA
In 1810 a German physician, Franz Joseph Gall (1758-1828), published the first volume of a four-volume treatise on the nervous system. In it he stated that the gray matter on the surface of the brain and in the interior of the spinal cord was the active and essential part, and that the white matter, deeper in the brain and on the surface of the spinal cord, was connecting material. In this he was correct.
Gall believed that the shape of the brain had something to do with mental capacity and that different parts of the brain were involved with different parts of the human body. There was something to this, too, but Gall went much too far. He believed he could correlate the shape of the brain with all sorts of emotional and temperamental qualities and that the shape of the brain could, in turn, be deduced from the superficial unevennesses of the skull. This marks the beginning of the pseudoscience of phrenology (from Greek words meaning "study of the mind") in which character is supposedly analyzed by feeling the bumps on the head.
The Brain Recorder
1929 AD
GERMANY
Dutch physiologist Willem Einthoven (1860-1927) had developed methods for detecting the rise and fall of electric potentials involved in the heartbeat and devised the electrocardiogram in 1903.
The German psychiatrist Hans Berger (1873-1941) thought the same might be done for the brain. During the 1920s he devised a system of electrodes that, when applied to the skull and connected to an oscillograph, would give a recording of the rhythmic shifting of electric potentials commonly called brain waves.
In 1929 he published his results, describing alpha waves and beta waves. In this way, electroencephalography (Greek for "the writing of brain electricity") was developed. It offered a technique for the diagnosis of such serious brain disorders as tumors and epilepsy.
:Raised Bread
1800 BC
CAIRO, EGYPT
Fruit juices that are left standing will sometimes ferment; that is, undergo changes that alter the taste. The same is true of moistened grain. Human beings, driven by thirst or hunger, might consume such fermented materials and then find that they liked the taste and the aftereffects. They were, of course, consuming alcohol, formed from sugars and starches by yeast, and they would grow elated as a result, because somewhat intoxicated. (This is not an exclusively human trait. Birds and animals will sometimes greedily feed on fermented fruits and become obviously intoxicated too.)
This may have happened in prehistoric times, but by 1800 B.C. the use of fermented materials was so common that laws had to be passed directing what was to be done in the case of misdeeds committed under the influence of too much beer.
From the beginning of agriculture, grain was converted into flour, which was moistened and made into flat, hard, but nourishing bread. Every once in a while, though, the moistened dough fermented and released gases (carbon dioxide) that caused the bread to rise and grow spongy. The result was leavened bread (from a Latin word meaning "to rise"), which was just as nutritious as flat bread but softer and much more pleasant to eat.
The Egyptians discovered this not long after 1800 B.C. and eventually learned that the process could be controlled. If some of the fermenting bread was saved before it was baked and added to dough that had not yet begun to ferment, the fresh dough would ferment in its turn. One would not have to depend on chance.
≤A Line of Bubbles
1953 AD
DETROIT, MICHIGAN
At this time the most familiar device for detecting the paths of subatomic particles was the cloud chamber invented by Scottish physicist Charles Thomson Rees Wilson (1869-1959). The American physicist Donald Arthur Glaser (b. 1926) thought of reversing its principle.
In the cloud chamber, you have humid air on the point of forming small droplets of liquid. What if you started, instead, with a liquid that was on the point of boiling and forming small bubbles of vapor? In the cloud chamber, a speeding charged particle would encourage the formation of droplets, and a line of droplets would mark out its path. In this new bubble chamber, a speeding charged particle would encourage the formation of bubbles, and a line of bubbles would mark out its path.
Since liquids are denser than gases, a speeding particle will slow more quickly in a bubble chamber than in a cloud chamber, curve more intensely, and reveal its properties more clearly. Then, too, there will be more collisions in the bubble chamber -- more events will take place. Finally, if liquid hydrogen is used as the liquid, it will consist, for the most part, of electrons and single protons, and the simplicity of the background will make the results easier to interpret.
Math in Your Pocket
1971 AD
DALLAS, TEXAS
In 1971 Texas Instruments placed on sale the first calculator that was easily portable. Making use of transistorized circuits, it weighed only 2-1/2 pounds and cost merely $150. In subsequent years, both the weight and the cost decreased dramatically.
çGunpowder in a Tube
1346 AD
CRECY, FRANCE
Once the Europeans got their hands on gunpowder, it didn't take them long to place it in a strong metal tube from which its explosive force could hurl out a ball of rock or metal much more forcefully than any catapult could manage. We don't know who first attempted to build these tubes, or cannon (from the Italian word for "tube"). Some claim that primitive cannons were used at a siege of the city of Metz in 1324.
There is no doubt, however, that they were in use by 1346. Edward III of England, intent on claiming the throne of France, went to war in 1337 over the matter, thus beginning what was eventually to be called the Hundred Years War.
The first great land battle of the war was at Crécy in north-central France on August 26, 1346. The French outnumbered the English, particularly in mounted knights. The French also had crossbow archers from Genoa. The English, however, had longbow archers, and it was no contest. The English archers had it all their own way, and the French were massacred. Edward III also had cannon at Crécy. They were primitive things and accomplished nothing -- but they were a portent of the future.
ìEarly Artillery
400 BC
SYRACUSE, SICILY
The Greeks of this period were good at war. They had developed hoplites (from a Greek word for "heavy shield"), or heavily armed foot soldiers. The hoplites' helmets, breastplates, and leg armor were made of good steel. They carried a shield on one arm (instead of around the neck) and a sword in the other. They also had long spears to thrust with, rather than to hurl. They were trained to fight in close formation as a unit -- it was not the individual champion but the weight of the entire formation that counted. A line of hoplites could wipe out the lightly armed disorderly mob that made up most non-Greek infantry, and it was for that reason that the Greeks managed to defeat the enormous Persian Empire.
The most important Greek city in the West was Syracuse, on the eastern coast of Sicily, which reached its period of greatest power under Dionysius (reigned 405-367 B.C.). He encouraged work on new weapons, and about 400 B.C. his workers devised the catapult (from Greek words meaning "to hurl down"). In its first form it was like a giant bow that was immobile and took many men to cock. When it was released, however, it hurled down upon a city's walls, not a little arrow but a huge rock -- or hurled it over the wall and into the city.
It was the first long-range weapon that could hurl heavy objects, or the first piece of artillery (from a French word relating to a bow, which was the first long-range weapon).
The one big disadvantage of the catapult was its slowness. The enemy could see the cocking going on and had plenty of time to prepare for the blow or avoid it. Nevertheless it was a premonitory example of things to come.
Writing in Color
1906 AD
RUSSIA
The Russian botanist Mikhail Semenovich Tsvett (1872-1919) worked with plant pigments, which are made up of a large number of rather similar organic compounds, difficult to separate into individual substances that can be studied singly. (This is a difficulty that frequently arises in biochemistry.) In 1906 Tsvett found a convenient means of separation. He let a solution of a mixture of the pigments trickle down a tube of powdered aluminum oxide. The different substances in the pigment mixture held onto the surface of the powder particles but with different degrees of strength. As the mixture was washed downward, the substances began to separate, those holding with less strength being washed down farther.
If the tube of aluminum oxide was long enough, the substances in the mixture would be completely separated by the bottom of the column, and they would be washed out individually. The separation could be judged by the appearance of different shades of color on the column, so the technique was called chromatography, from Greek words meaning "writing in color." The name was retained even in the case of mixtures of colorless substances. Chromatography, modified in many ways, became one of the most important techniques for the study of complex mixtures.
╞The Map of You
1911 AD
NEW YORK, NEW YORK
American geneticist Thomas Hunt Morgan (1866-1945) had shown that chromosomes could cross over from one gene to another, which allowed them to be inherited separately where previously they had been linked, or inherited together. Obviously, the farther two genes were from each other on a particular chromosome, the greater the chance that a crossover somewhere along the chromosome would separate them.
Morgan and his assistant, the American geneticist Alfred Henry Sturtevant (1891-1970), investigated the frequency of separation by crossover in an attempt to locate the genes governing particular characteristics on a chromosome. The first such chromosome map was presented in 1911.
▌No More Drippy Clocks
1335 AD
MILAN, ITALY
The first advance over the water clock came in the fourteenth century. Instead of being driven by a rise in water level, the dial on the clock face was driven by the downward pull of gravity on weights. The resulting mechanical clocks did not tell time more accurately than water clocks did, but they were more convenient and required less care. They could be mounted in a tower (either of the city hall or of the town church) for all to see. One was erected in Milan, Italy, in 1335, for instance. It struck the hour, and for the first time citizens could learn the time (to the nearest hour, at any rate) by listening to the number of times the bell rang. (The very word clock is from the French word for "bell.")
Round Yes, But Much Bigger
1492 AD
SPANISH COAST
While the Portuguese were working their way around Africa, there were those who felt that the same result could be achieved another way. Since it was understood that the Earth was spherical, it was bound to occur to people that it might be circumnavigated and that the Far East could be reached by sailing west.
The concept was a simple one and, in fact, it had been suggested by Roger Bacon (ca. 1220-1292) two centuries before. What stopped people from making the effort was the thought that between the western coast of Europe and the eastern coast of Asia might be a vast stretch of ocean that the ships of the day could not be expected to manage.
If Eratosthenes (ca. 276-ca. 194 B.C.) was correct and the Earth was 25,000 miles in circumference, then between Europe and Asia were some 12,000 miles of unbroken sea. Yet other authorities, such as Ptolemy (2nd century), had thought the Earth was smaller than that, and Marco Polo (1254-1324) had thought that Asia extended farther east than it really did.
Combining a smaller Earth with a more eastward Asia, an Italian navigator, Christopher Columbus (1451-1506), was convinced that a westward trip from Europe to Asia was a matter of only 3,000 miles. He thought this could be managed, and he shopped about the various nations of western Europe for financial support so that he could outfit an expedition.
Portugal was a natural target, of course, but the Portuguese experts thought the Earth was larger than Columbus's figure (the Portuguese were right) and were convinced it would not be long before they circumnavigated Africa and reached their goal.
Columbus tried elsewhere without luck and was almost on the point of giving up when things turned out well for him in Spain. With Ferdinand and Isabella ruling jointly over a united Spain, the nation could assault the last scrap of Muslim rule. This was the nation of Granada in the far south of Spain. The joint monarchs prosecuted a vigorous war against Granada and on January 2, 1492, it fell. What's more, Torquemada engineered the expulsion of the Jews from Spain in 1492.
The Spanish monarchs, feeling Spain to be united and strong, decided to give Columbus a minimum of financial backing. With three old ships and a crew of prisoners released from jail for the purpose, he set forth on August 3, 1492. For seven weeks he sailed westward, encountering no land but also encountering no storms. Finally on October 12, he sighted land -- an island, as it turned out, in the Bahamas.
He sailed southward and encountered islands of the West Indies. (To his dying day, Columbus was convinced he had reached the Indies; that is, the eastern coast of Asia. The name of the West Indies and the habit of calling Native Americans Indians are the result of that delusion.) It was not Asia, of course, that he had come upon, but the American continents, a New World, and the Old World would never be the same again.
Columbus was not, of course, the first human being to set foot on these continents. Siberian natives had done so at least thirty thousand years earlier. He was not even the first European to do so, for Leif Eriksson had done it five centuries before. Columbus's feat, however, led almost at once to the beginning of permanent European settlements on the new continents, and that marked their entry into the common current of world history. It is for this reason that Columbus is generally given credit for the "discovery."
Incidentally, the fact that new continents existed that were wholly unknown to the ancients helped eliminate the notion that the ancient thinkers had known everything and had solved all problems. Europeans gained the heady feeling that they now moved beyond the ancients, and that helped make possible the Scientific Revolution that was to start in half a century.
╘Bill, Giotto and Halley's Comet
1705 AD
GERMANY
A little over half a century before, English astronomer Edmond Halley (1656-1742) had predicted that the comet of 1682 would return in 1758. The amateur astronomer Johann Georg Palitzsch (1723-1788) set up his telescope and trained it on the part of the sky where the comet was expected to appear, if it did return. On December 25, 1758, he spotted it, and once the news broke, professional astronomers zeroed their instruments in upon it. The comet has ever since been known as Halley's comet, or in line with the conventions of the present day, Comet Halley.
Calculating backward, Halley's comet turned out to be the one that appeared at the time of the invasion of England by William of Normandy. It was also the comet that Italian artist Giotto di Bondone painted in 1304. The return of Halley's comet suddenly made comets the headliners of astronomy, and for several decades it seemed that the greatest feat any astronomer could achieve was to discover comets.
óPlotting Comets
1472 AD
GERMANY
Comets had always been viewed with such terror that almost no one had been able to observe them rationally. Then in 1472, when a bright comet appeared in the sky, a German astronomer, Johann Müller (1436-1476), refused to allow himself to be governed by fear. (He is better known by his self-chosen name of Regiomontanus, which means King's Mountain, as does the German name of his birthplace, Königsberg.)
Regiomontanus observed the comet from night to night and noted its position against the stars. In this way, for the first time, the exact path of a comet across the sky was plotted. It marked the beginning of rationalism with respect to those bodies.
╥Base Two Versus Base Ten
1700 AD
HANOVER, GERMANY
Our system of positional notation for numbers is based on ten, undoubtedly because we have ten fingers on our two hands. There is, however, nothing magic about the figure 10. Instead of units, tens, hundreds (10 x 10s), thousands (10 x 10 x 10s), and so on, we could have units, eights, sixty-fours (8 x 8s), five-hundred-twelves (8 x 8 x 8s), and so on, or ones, seventeens, two-hundred-eighty-nines (17 x 17s), four-thousand-nine- hundred-thirteens (17 x 17 x 17s), and so on -- or any number.
This was pointed out by German mathematician Gottfried Wilhelm Leibniz about 1700. Some bases for positional notation are, of course, more convenient than others. Using the base 12 or 8 each has some advantages over 10. Leibniz also showed that the binary system based on 2 had its uses. Its positions were units, twos, fours, eights, sixteens, and so on. The only symbols it needed were 1 and 0. The binary system is particularly useful for modern computers.
²Helicopter: As Slow as You Like
1939 AD
STRATFORD, CONNECTICUT
One problem with airplanes is that they must move quickly in order to produce aerodynamic lift under their wings. If they slow up, the lift dwindles and they crash. A device that exerted a force straight upward instead of merely forward as propellers do would eliminate this necessity for speed-born lift. The obvious solution was a large propeller directly overhead. Since the ends of the propeller would mark out a helix as the vehicle lifted upward, such a device was called a helicopter, from Greek words meaning "helical wing."
The Russian-born American aeronautical engineer Igor Ivan Sikorsky (1889-1972) had been working with helicopters for thirty years and finally in 1939 produced a satisfactory model. On September 14, a helicopter with Sikorsky himself at the controls flew successfully. The time was to come when it would be a primary weapon in wars fought in Vietnam and Afghanistan, to say nothing of its uses in tracking traffic, rescue work, and intra-urban transportation.
fThe Unintended Consequence
1793 AD
UNITED STATES
The new textile industry of Great Britain, and the one that was just beginning to arise in New England, meant increasing demands for cotton, which could be grown with great profusion in the southern states. However, it was difficult to pull the cotton threads off the seeds in the cotton bolls, and that limited the quantity that could be produced.
In April 1793, however, an American inventor, Eli Whitney (1765-1825), challenged to do something about the problem, invented the cotton gin (gin is short for engine). It was a simple device in which metal wires poked through slats and entangled themselves in the cotton fibers. The wires were affixed to a wheel, and as the wheel turned, the cotton fibers were pulled off. One gin could produce 50 pounds of cleaned cotton per day.
The effect on the United States was catastrophic. The southern states began to produce cotton in great quantities, and slaves were needed, also in great quantity, to pull the bolls off the plants so that the gins would have enough to work on.
The southern states, which had been giving up on slavery, had to return to it now, defend it, and work up all sorts of excuses for its existence. They developed an agricultural economy based on slave labor, which kept them poor, while the northern states grew rich on wheat and industry. And in the end, it brought on the Civil War.
ÇWhat's in the Middle?
1473-1543 AD
CRACOW, POLAND
The speculations of Aristarchus in 280 B.C. about a heliocentric system in which the Sun was at the center of the Universe, with the planets, including the Earth, revolving about it, had been disregarded, and the geocentric system of Hipparchus (150 B.C.) and Ptolemy (140 A.D.) had been accepted without question.
However, the mathematics needed to work out the planetary motions on a geocentric basis was very difficult. While the Sun and Moon moved steadily west- to-east against the stars, the other planets occasionally reversed direction (retrograde motion) and grew markedly brighter and dimmer as they progressed across the sky.
The Polish astronomer Nicolaus Copernicus (1473-1543) thought, as early as 1507, that if one went back to Aristarchus's view and supposed that all the planets, including Earth, were moving about the Sun, it would become easy to explain retrograde motion. It would also be easy to explain why Venus and Mercury always remained near the Sun and why planets grew dimmer and brighter. In addition to all this, the mathematics for working out planetary motions and positions would be simplified.
m The Skillful Early Artists
20,000 BC
ALTAMIRA, SPAIN
Sometime after 50,000 B.C., a variety of Neanderthal existed with less pronounced eyebrow ridges, even in male adults, with a high forehead and a distinct chin, and with smaller teeth. In short, this was the kind of hominid, quite exactly, that we are. We are Homo sapiens sapiens, and we are sometimes referred to as modern man, though modern human beings is more appropriate terminology to make it clear that men, women, and children are meant and not only men.
Between 50,000 B.C. and 30,000 B.C., the two varieties of Homo sapiens coexisted, but by the latter date, some interbreeding and probably a great deal of slaughter had put an end to the Neanderthals, so that for the last thirty thousand years or so, all living hominids have been of the modern type.
Modern human beings were extremely successful. For the first time, they extended the range beyond where Homo erectus had left it. Between 40,000 B.C. and 30,000 B.C., human beings took advantage of the existence of land bridges that the fall in sea level had produced. They entered Australia from southeastern Asia, and North America from northeastern Asia. No hominids had existed in either continent before. They also found their way to the Japanese islands.
The new lands were steadily overrun, and by 10,000 B.C. human beings had reached the southernmost part of South America, and even Tierra del Fuego, the island to the south of that continent. All the continental areas except Antarctica and the glaciated areas in the north were settled.
Human beings were hunters, of course, and they had developed rituals to improve their success. One, apparently, was to draw pictures of animals being successfully hunted, in the conviction, perhaps, that life would imitate art, or that the spirits that animated animals would be mollified in this way and would cooperate.
In 1879, a Spanish archaeologist, Marcellino de Sautuola (d. 1888), was excavating Altamira Cave in northern Spain, when his twelve-year-old daughter, who was with him, spied paintings on the ceiling and cried out "Bulls! Bulls!"
There were paintings of bison, deer, and other animals in red and black, drawn perhaps as long ago as 20,000 B.C., similar to those seen here drawn in the caves at Lascaux, France.
The drawings spoke highly of the artists' skill. If anything were needed to show that early human beings were our intellectual equals, this would do. In the last twenty millennia, we have gained enormous knowledge and experience, but we are not one whit more human than those ancient cave artists.
So excellent was the art, in fact, that many people refused to believe it was truly ancient. Many felt it to be a fraud of some sort, a modern hoax. It was only with the finding of other caves and other cave paintings that the art was finally accepted as ancient.
The cave paintings were found in remote places and were invisible except by artificial light, so that it is believed they were drawn for religious and ritualistic purposes rather than for display. Nevertheless, they are clearly the result of infinite pains, and it is hard to believe that the artists did not derive joy from their work.
`Curie Finds Uranium Radioactive
1897 AD
PARIS, FRANCE
One of those who followed up instantly on the 1896 discovery by French physicist Antoine-Henri Becquerel (1852-1908) of the radiation from potassium uranyl sulfate was a Polish-born French chemist, Marie Sklodowska Curie (1867-1934). She was the wife of French chemist Pierre Curie.
In 1897 she made use of her husband's discovery of piezoelectricity to measure the intensity of radiation given off by a variety of uranium compounds. She showed that the intensity was always in proportion to the quantity of uranium present.
This demonstrated that the radiation did not come from the compound as a whole, but from the uranium atom specifically. It was an atomic phenomenon and not a molecular one.
Marie and Pierre Curie continued to work on the radiations produced by uranium.
In 1898 Marie Curie showed that thorium, another heavy metal, also produced radiations, and she coined the term radioactivity for the phenomenon, so that it could be said that both uranium and thorium were radioactive.
She also discovered that although pure uranium compounds were always radioactive only to the extent that uranium was present, some uranium ores produced far more radioactivity than could be accounted for by the uranium present. It seemed to her that the ores must contain other elements (in small quantities or they would have been discovered earlier) that were much more intensely radioactive than uranium.
In July 1898 the Curies detected such an element, which they called polonium after Marie Curie's native land. In December 1898 they detected another, which they called radium because of its intense radioactivity.
For their work on radioactivity, the Curies shared the Nobel Prize for physics with Becquerel in 1903. For the detection of polonium and radium, Marie Curie (her husband by then being dead) received the Nobel Prize for chemistry in 1911.
x
Survival of the Few
1859 AD
DOWN, UNITED KINGDOM
The British biologist Charles Robert Darwin (1809-1882), like many biologists, believed that life forms had evolved; that some species, with time, changed into other related species, while some species became extinct.
What puzzled Darwin was the mechanism that drove evolution onward. In 1838 he read Malthus and realized that not only human beings multiplied past the food supply available, but that all living things did.
Therefore, in each generation, there was a competition for survival among the too-many, and those tended to survive who could snatch enough food, or best evade a predator. In short, nature itself would select a few from the many for survival. The characteristics that made survival likely would be inherited by the offspring of the survivers and again there would be a natural selection.
Darwin assumed that there were always variations among offspring, random and tiny variations perhaps, and that nature then used those variations as a means of selection, so to speak. The "better" among the variations would not always do better, since there was always the factor of chance, but on the whole, and in the long run, they would.
Darwin was theorizing, then, on evolution by natural selection. Knowing that this idea would create enormous controversy, and being a gentle person who could not bear to participate in such controversy, he spent some twenty years gathering evidence for his point of view, hoping that when he did publish, the evidence would be so overwhelming that it would preclude argument (though in this he was naive).
In 1858 another British biologist, Alfred Russel Wallace (1823-1913), was in the East Indies. He too had read Malthus and arrived at the notion of evolution by natural selection. Unhampered by Darwin's fear of controversy, Wallace wrote up his theories in three days. Then, in order that his views might be checked by an appropriate expert, he sent his eleven-page paper to Darwin, who could scarcely believe his eyes when he saw himself so anticipated.
There was nothing for Darwin to do but to suggest a joint publication and this was carried through immediately. In the next year, 1859, Darwin reluctantly published a book, best known as The Origin of Species, in which he presented his theory in detail (but not in as much detail as he would have liked, for he had been planning a book five times as long at least). Darwin's book was the most notable scientific work since Newton's great classic. It was the foundation of a new biology, as Newton's had been the foundation of a new physics. It changed the very current of people's thinking, and the world has never been the same.
nAn Electronic Gate
1906 AD
YALE, NEW HAVEN, CONN
The rectifying diode worked out by British electrical engineer John Ambrose Fleming (1849-1945) was a useful tool but limited in its range. That range was extended in 1906 by the American inventor Lee De Forest (1873-1961). He inserted a third element, called a grid, into the tube to make it a triode (three electrodes).
The grid is an electrode with holes in it, so that electrons can move from the hot filament through the holes of the grid to the plate. Even a weak charge placed on the grid can have a relatively enormous effect on the electron current. It can increase the intensity of the current if the grid is slightly positively charged, since it then attracts electrons from the heated filament; and it can decrease the intensity if slightly negatively charged, since it then repels electrons. By placing a small varying charge on the grid, you get a much larger variation in the electron flow.
A triode therefore acts as an amplifier, and it can be modified to perform a great variety of tasks. Radio became more than ever adapted to the transmission of sound through Fessenden's modulation.
,Locating Any Point on a Plane
1637 AD
PARIS, FRANCE
The French mathematician René Descartes (1596-1650) published, in 1637, his Discours de la méthode (Discussions on the Method) -- of finding scientific truth by good reasoning, that is.
In a hundred-page appendix to this book, Descartes combined algebra and geometry. He pointed out that if one drew two perpendicular straight lines, marked the intersection 0, and laid off units on each line, positive numbers to the right and up, negative numbers to the left and down, then every point in the plane could be represented by two numbers, one for its position along the horizontal axis and the second for its position along the vertical axis. (One could add a third axis, in and out, and locate every point in the Universe by three numbers.)
Straight lines and curves could then be expressed by algebraic equations, which would locate every point on the line or curve with reference to the two axes. This combination of disciplines, producing analytic geometry, strengthened both. Geometric problems could be solved algebraically, and algebraic equations could be illustrated geometrically.
It also laid the foundation for the development of the calculus, which is essentially the application of algebra to smoothly changing phenomena that can be represented geometrically by curves of various sorts.
òIgnition by Compression
1897 AD
MUNICH, GERMANY
The four-stroke engine invented by German engineer Nikolaus August Otto (1843-1910) used low-boiling gasoline for fuel and ignited the vapor-air mixture with an electric spark.
A German inventor, Rudolf Diesel (1858-1913), tried to eliminate the complexities that resulted from running an electrical system in conjunction with an engine. By 1897 he had perfected a Diesel engine that ignited the vapor-air mixture by the heat developed through compression. This allowed him to use higher-boiling fuel such as kerosene, which was cheaper and less inflammable (hence safer) than gasoline.
However, the compression had to be great, so the Diesel engine had to be considerably larger and heavier than the Otto engine if the higher pressures were to be brought about and maintained. Diesel engines therefore found their use in heavy transport vehicles such as trucks, buses, locomotives, and ships.
@ Why 60 is so Handy
1800 BC
SUMERIA (IRAQ)
The concept of mathematics is as old as human beings. Even some animals have a primitive number sense. It is certainly difficult to believe that the pyramids, for instance, could have been built without substantial ability in geometry.
The Sumerians, and the Babylonians who succeeded them, were the first to make significant advances in mathematics and in astronomy. By 1800 B.C., they had developed a number system based on 60 that we still follow in some ways, since we still have 60 seconds to the minute and 60 minutes to the hour. Why 60? Because it can be evenly divided by 2, 3, 4, 5, 6, 10, 12, 15, and 30, thus eliminating the frequent need of fractions -- with which the ancients had trouble.
In addition, there are 360 degrees (6 x 60) in the circle. Again, it is a number easily divided. In addition, the Sun takes 365 days to move completely around the sky, so that it travels, relative to the stars, just about 1 degree per day. That too may have influenced the choice of 360.
The sky-watchers of the Tigris-Euphrates valley eventually discovered that, in addition to the Sun and Moon, five bright stars changed position against the remaining "fixed" stars. These moving stars, which we call planets (from a Greek word for "wandering") were given the names of gods and goddesses, and we still do that today. We call the five bright stars Mercury, Venus, Mars, Jupiter, and Saturn. The presence of seven such planets (if we include the Sun and the Moon) gave rise to the seven-day week, with one of the planets in charge of each day. The week as a unit of time was thus instituted by the Babylonians and was adopted first by the Jews, then by the Christians, and through them, by virtually all the modern world.
The seven planets had paths around the sky, paths that passed through certain conglomerations of stars that were termed, in total, the zodiac by the later Greeks. This was divided into twelve constellations, so that the Sun remained in each constellation for about a month. Eventually the Sumerians and Babylonians worked out the pathways in some detail and could predict, in at least a rough manner, where the planets would be at future times. That represented the beginning of mathematical astronomy.
Since the Sun affected the Earth profoundly, making the difference between the day and night, and the Moon's phases marked the length of the month, it seemed natural to suppose that the other planets also had significance to human beings. Imaginative suggestions were made about the influence of each, as it varied in position with respect to the stars and other planets, and an intricate system of foretelling the future from planetary positions was evolved. This is astrology.
Astrology is not true, but people strongly want the security of knowing the future, so that even today astrology is accepted by many people.
eThe Wonders of Science
WELCOME TO SCIENCE ADVENTURE
Copyright (c) 1992 Knowledge Adventure. Text from Asimov's Chronology of Science and Discovery. Copyright (c) 1989 by Isaac Asimov.
Science Adventure takes you on a wild tour of great achievements throughout time and space!
In it, noted science and science fiction writer Isaac Asimov brings his particular blend of knowledge, wit, clarity and informed speculation to the great themes of scientific discovery and invention, from how early hominids may have begun to walk on two feet to the latest in space exploration.
To begin your adventure, just click!
ABOUT THE AUTHOR
Isaac Asimov was born in the Soviet Union in 1920, was brought to the United States in 1923, and became an American citizen in 1928. He was educated in the public school system of New York and obtained his B.S. in 1939, his M.A. in 1941, and his Ph.D. in 1948 -- all in chemistry, all from Columbia University.
He was professor of biochemistry at Boston University School of Medicine but hadn't worked at it since 1958.
He grew interested in science fiction in 1929 and sold his first story to a magazine in 1938. His first book appeared in 1950. Since his first sale he wrote and sold 371 short pieces of fiction and some 3,000 nonfiction essays.
He published more than 425 books of science fiction and nonfiction covering every branch of science and mathematics, history, literature, humor, and miscellaneous subjects.
He lived in New York City and was married to Janet Jeppson Asimov, a psychiatrist and also a science fiction writer. He had two children by an earlier marriage.
Asimov died on April 6, 1992.
UThe Twisting Strings of Life
1953 AD
CAMBRIDGE, ENGLAND
The work of American biochemist Erwin Chargaff (b. 1905) and English biophysicist Rosalind Elsie Franklin (1920-1958) in 1952 had supplied the information necessary to work out the structure of DNA. The key conceptual step was then taken by the English physicist Francis Harry Compton Crick (b. 1916) and the American biochemist James Dewey Watson (b. 1928). They made use of a key X-ray diffraction photograph taken by Franklin and made available to them by her boss, the New Zealand physicist Maurice Hugh Frederick Wilkins (b. 1916), apparently without Franklin's knowledge or permission.
In 1953 Watson and Crick suggested that DNA consisted of two chains of nucleotides arranged as a double helix, with the purine and pyrimidine bases facing each other and the phosphate links on the outside. Each two-ringed purine faced a one-ringed pyrimidine, so that the space between the two strands was constant. Adenines and thymines were paired, as were guanines and cytosines (thus accounting for Chargaff's results). Each strand of the double helix was a model (or template) for the other. In cell division, each DNA double helix would separate into two strands, and each strand would build up its complementary strand on itself; an adenine fitting over every thymine on the strand, a thymine over every adenine, a guanine over every cytosine, and a cytosine over every guanine. In this way two double helixes would appear where there had been one before. Thus DNA underwent replication without changing its structure except for very occasional accidental errors, which represented mutations.
The Watson-Crick structure made so much sense that it was accepted at once. Watson, Crick, and Wilkins shared the Nobel Prize for physiology and medicine in 1962 as a result. By that time Franklin was dead, and her involvement did not have to be considered.
φFirst First Aid
1550 BC
EGYPT
People are sure to get sick at times, or have accidents and be hurt. The problem of getting well, or being made well, naturally concerns everyone. To aid the coming of wellness, people might attempt to conciliate various gods by proper incantations or rituals, make use of various forms of ritualized behavior, or use parts of plants or animals thought to have curative value.
The first written compilation of such cures that we know of is an Egyptian papyrus dated about 1550 B.C. It was discovered in 1873 by a German archaeologist, Georg Moritz Ebers (1837-1898), and is called the Ebers Papyrus in consequence. It contains about seven hundred magical remedies and descriptions of folk medicine for the treatment of various ailments.
uLess Than Nothing
1545 AD
ITALY
Until 1545, mathematicians had assumed that all numbers, whether integers, fractions, or irrationals, had to be greater than zero. It might seem, after all, that one could not possibly have less than nothing.
On the other hand, mathematicians knew there were such things as debts. To have no money and to owe a sum to someone else means having less than no money.
This might seem merely like practical business, nothing to do with ethereal numbers, but Italian mathematician Geronimo Cardano (1501-1576) showed, in 1545, that debts and similar phenomena could be treated as negative numbers, which would follow rules of mathematics very similar to those that ordinary numbers did. You could have negative integers, negative fractions, and negative irrationals.
In that same year, Cardano worked out a general solution for equations of the fourth degree, involving x^4.
A Boy and His Dog
12,000 BC
IRAQ
In the 1950s, fossil remains of dogs were found along with remains of humans in caves near Kirkuk in what is now northern Iraq. They dated from about 12,000 B.C.
How dogs came to be domesticated is not known, of course. My own guess is that, again, children were responsible. A child could form a close bond with a puppy that had been found abandoned, or that was left over when the mother was killed either in self-defense or for food. Once the bond was formed, the child would object strenuously to the use of the puppy as food, and parents might oblige.
It would quickly have turned out that dogs, being hunters and pack animals, will accept a human master as the pack leader. Dogs would go hunting with their masters, help in killing the game, wait for the human beings to take what they wanted, and be satisfied to be thrown a minor share. In this way human beings, for the first time, obtained the services of another species of animal.
By 10,000 B.C., another step had been taken, with the domestication of goats in the Middle East. The goats would be cared for, fed, and encouraged to reproduce. They would supply milk, butter, and cheese and, by dint of judicious culling, meat. What's more, since goats eat grass and other substances humans find inedible, the food supply was increased at no cost. (Dogs have to be given food that would otherwise fill human stomachs.)
Until then, people had found their food by hunting and gathering, with all the insecurities attendant on that. Herding provided a much more secure food supply.
KFrisky Mice Discover Oxygen
1774 AD
ENGLAND
Joseph Priestley (1733-1804) worked with mercury in his collection of gases and could not help using it more directly in his experiments. Mercury, when heated in air, will form a brick-red compound, which we now call mercuric oxide. Priestley heated some of this compound in a test-tube by using a lens to concentrate sunlight upon it. When he did this, the compound broke up, liberating mercury, which appeared as shining globules in the upper portion of the test-tube.
In addition, a gas was given off that possessed most unusual properties. Combustibles burned more brilliantly and rapidly in it than they did in ordinary air. Mice placed in an atmosphere of this gas were particularly frisky, and
Priestley himself felt "light and easy" when he breathed it. When Lavoisier heard of the experiments of Priestley and of Rutherford, he realized in the light of his own experiments that air must consist of a mixture of two gases: one-fifth was Priestley's gas, which Lavoisier named oxygen (from Greek words meaning "acid producer," because it was mistakenly felt at the time that all acids contained oxygen), and four-fifths were Rutherford's gas, which Lavoisier named azote (from Greek words meaning "no life"), but which later came to be known as nitrogen.
Clearly, it was oxygen that supported combustion and animal life and oxygen that was involved in rusting. Animals must consume oxygen and produce carbon dioxide, and from Priestley's earlier experiment, plants must consume carbon dioxide and produce oxygen. Between these two forms of life, the atmosphere's makeup remained stable.
ΘThe Brilliant Snail
1200 BC
TYRE, PHOENICIA
The human urge to beautify is irresistible, and since we can see colors, we usually find them, singly and in combination, to be more attractive than black and white. The Old Stone Age artists used colored earths to make their paintings.
As early as 3000 B.C., dyes were used to color otherwise white or yellowish cloth, both in Egypt and in China. Indigo, a blue color extracted from a plant, was used and madder, a red color extracted from the root of another plant. By 1400 B.C., cloth could be dyed in virtually all colors.
The chief trouble with most early dyes was that they tended to bleach in the sun and to wash out in water, so that dyed fabrics quickly grew dim and blurred.
One dye that was very resistant both to sun and water was obtained from a snail in the eastern Mediterranean. To obtain the dye was a tedious task, but the resultant red-purple color was brilliant and stayed brilliant. The city of Tyre in Phoenicia had developed this dye industry by 1200 B.C. so that the color was called Tyrian purple. Between the difficulty of amassing a quantity of it, and its great desirability, its price went sky-high, but it still sold, albeit only to the rich and powerful. Tyre grew wealthy out of its dye trade and was able to support its merchant fleet and undertake trading ventures that made it richer still.
Some believe that the Greek name Phoenicia, applied to the land in which Tyre was a city, came from a Greek word meaning "red-purple" in reference to the dye.
5Earth: Home Sweet Home
1989 AD
THIRD PLANET, SOLAR SYSTEM
You may have heard that Earth is a mere speck near the edge of our galaxy, and that is true. But don't underestimate Earth, it is actually an amazing -- but delicate -- little planet.
As many environmentalists have pointed out, Earth's atmosphere has just the right amount of ozone and carbon dioxide. If there was much more or less of either, Earth's surface would be too hot or cold.
Or, suppose Earth was a bit closer to the sun. The added heat would prevent the clouds from raining. But move it a little further away and too little water would evaporate from the oceans, so clouds would not form.
If you painted the Earth's surface a darker color, it would absorb too much heat. But paint it a lighter color and the surface would reflect too much heat and become too cold.
While Earth is small, it's distance from the sun and tilt and rotation and gravity and many other factors make it ideal for life.
This wonderful planet is a slightly flattened ball measuring about 24,860 miles around at the equator. It is covered with a 5- to 40-mile thick crust divided into plates that slide slowly around on the mantle, a mass of hot, gooey rock surrounding a core of molten metal.
Because Earth is slightly tilted in relation to the sun, either its north or south end is closer to the sun at any time. Sunlight strikes the closer end more directly and intensely, causing summer, and strikes the further end at a greater angle and less intensely, causing winter.
Today, many scientists are encouraging us to change our lifestyles so we don't upset the delicate balance that makes Earth a wonderful place to live. They are concerned that some human activities, such as burning fossil fuels, clearing forests and releasing man-made chemicals into the atmosphere, may upset the planet's environment.
╚Measuring the Earth
1684 AD
FRANCE
Eratosthenes' figure for the circumference of the Earth in 240 B.C. had not been bettered in a thousand years.
In 1684, however, certain observations of the French astronomer Jean Picard (1620-1682) were published posthumously. Instead of noting the distance of the Sun from the zenith (the point in the sky that is directly overhead) at different places on the Earth by measuring its shadow, as Eratosthenes had done, Picard measured the distance of a star from the zenith at different places. With telescopes, that was the more accurate method, and Picard calculated the Earth's circumference as 24,876 miles and its diameter as 7,900 miles, figures that are very close to the best we have today.
╠The United States' Birthplace
1990 AD
Shown here is the Northeastern United States, the birthplace of the United States. People from Europe (particularly England and Germany) settled all along the northeast coast of the continent, and gradually spread westward.
The land was -- of course -- inhabited when the Europeans arrived, and unfortunately, conflicts often arose between settlers and Native Americans. And usually it was the Native Americans who suffered the most in these disputes.
Oh No! The Sun's Going Out
585 BC
MILETUS, ASIA MINOR
In studying the motion of the planets along the path of the zodiac, the Babylonian astronomers could not help but note that sometimes the motions would bring two of them fairly close together. This would be most spectacular in the case of the Sun and the Moon. Every once in a while the Moon would pass in front of the Sun and obscure part or sometimes all of it. At times, too, the Sun would be on one side of the Earth, and the Moon would be directly on the other. The Earth's shadow would then fall on the Moon, obscuring it. Thus, there could be either a solar eclipse or a lunar eclipse. (Eclipse is from Greek words meaning "to leave out," since when one happened, the Sun or the Moon would seem to be left out of the sky.)
An eclipse is a frightening spectacle. Those who become aware of it may actually think that the Sun or the Moon is dying, with incalculable consequences. Even if it is understood that the Sun or Moon is only obscured temporarily, there is a feeling that it is an omen of evil sent by the gods as a warning.
However, by studying the movements of the Sun and Moon, early astronomers learned to predict when eclipses would take place. Since that made the eclipses appear to be automatic and unavoidable phenomena, it removed their unexpected and ominous connotations. (There is some feeling that even prehistoric watchers of the sky learned to tell when lunar eclipses would occur, and that the stones at Stonehenge in southwestern England were arranged as a kind of observatory that allowed prediction of such phenomena.)
The Greek philosopher Thales (624-546 B.C.) seems to have learned the Babylonian methods and predicted an eclipse of the Sun, one that we now know (by calculating backward) took place on May 28, 585 B.C. This added greatly to Thales' prestige and also helped make eclipses less frightening, since they were demonstrated to be predictable.
)Farming: A Tiger by the Tail
8000 BC
MESOPOTAMIA
Human beings led a nomadic life. As long as hunting was a major source of food, they had to be prepared to follow migrating herds of animals. Even if they lived on plants and on nonmigrating animals, a tribe lingering in one place too long would consume the available food and have to move elsewhere for fresh foraging.
Even when human beings became herders, they remained nomads. The herds had to be taken to fresh pastures now and then, either because of seasonal changes or because of overgrazing.
About 8000 B.C., however, in the same region where animals were first domesticated, something new arrived, heralding a change greater than any since the first use of fire.
What it amounted to was that plants were domesticated. Somehow it occurred to human beings to plant seeds deliberately, to wait for them to grow, to water them, and to wait for them to ripen while destroying competing plants. Then the plants could be harvested and would serve as food.
It was tedious and back-breaking work, but the net result was that a great deal of food could be obtained, far more than by hunting and gathering, or even herding, since plant life is more copious than animal life.
The coming of herding and agriculture, particularly agriculture, meant that a given area of land could support a larger population than before. There was less starvation, more children survived, and the population increased.
Agriculture began in northern Iraq where wheat and barley grew wild, and it was these that were domesticated. The kernels of grain could be ground into flour that could be stored for months on end without spoiling and could be baked into a tasty and nutritious bread.
Agriculture, for the first time, condemned human beings to a sedentary existence. Once a farm was established, there could be no further wandering. The farmers had to remain with the farm, which was fixed in one place.
A sedentary life had its dangers. As long as human beings hunted and gathered, or even herded, danger could be avoided. If a hungry, marauding tribe approached, intent on taking what food they could find, the tribe already present, if they decided fighting would be too dangerous, could always flee. Farmers could not run, at least not without abandoning their farms and seeing their lifework ruined and themselves faced with starvation. Once the population had increased, thanks to agriculture, they could not possibly find enough food to maintain themselves except by continuing with agriculture -- they had a tiger by the tail.
Farmers therefore had to be prepared to fight at whatever cost, and they gathered together for mutual self-protection. They would find a site on an elevation (so that they could throw missiles downward, whereas an enemy would have to throw them upward, with lesser effect) and with a secure water supply (you can go without food for a period of time but not without water). There they would build houses and surround them with a protective wall. The result would be a city, and the inhabitants would be city-dwellers, or citizens.
In northern Iraq, for instance, near the site where herding and agriculture developed, are the remains of a very ancient city, founded perhaps in 8000 B.C., at a site called Jarmo. It is a low mound into which, beginning in 1948, the American archaeologist Robert J. Braidwood dug carefully. He found the remains of houses built with thin walls of packed mud and divided into small rooms. The city may have held no more than a hundred to three hundred people, but cities grew rapidly larger.
Agriculture made it possible for farmers to produce more food than their own families needed. This meant that people could do things other than farming -- for example, engage in artisanry or art -- and trade their products for some of a farmer's excess food. For the first time, human beings could find time to think of something other than the next meal. In addition, living in close quarters in a city, they could interact easily, and the innovations and ideas of one could be rapidly transmitted to the others. As a result, the coming of agriculture and of cities meant the coming also of a new and more complex way of life, which we call civilization (from a Latin word for "city-dweller"). The civilized area was small at first, but it spread outward steadily until it now occupies virtually the entire world.
G
It Depends Where You Sit
1905 AD
BERN, SWITZERLAND
The Michelson-Morley experiment of 1887 was still troublesome. The work of Irish physicist George Francis FitzGerald (1851-1901) and Dutch physicist Hendrik Antoon Lorentz (1853-1928) in 1895 got rid of the difficulty in a way, but the notion of decrease of distance and increase of mass seemed to hang in the air without an overall physical theory for support.
The German-born physicist Albert Einstein (1879-1955) supplied that in 1905. He began with the assumption that the speed of light in a vacuum would always be the same, regardless of the motion of the light source relative to the observer. This was what Michelson and Morley had observed, but Einstein maintained that he was unaware of the Michelson-Morley results when he worked out his theory.
From this assumption it was possible to deduce length contraction and mass increase with velocity. It was also possible to deduce that the speed of light in a vacuum was an absolute speed limit and that the rate of time-flow would decrease with velocity.
This is Einstein's theory of special relativity. It is relativity, because velocity has meaning only as relative to an observer, there being no such thing as "absolute rest" against which an "absolute motion" can be measured. There is also no such thing as "absolute space" or "absolute time," since both depend on velocity and therefore have meaning only relative to the viewer. Nevertheless, despite this absence of absolutes, the laws of physics still held for all "frames of reference." In particular, British mathematician James Clerk Maxwell's equations in 1865 still held, though the much older and more revered laws of motion as worked out by Newton had to be modified. The theory is special, because it confines itself to the special case of objects that are moving at constant velocity. Under those conditions, the theory does not take into account the effect of gravitational interactions, which are everywhere present and which force accelerations on motion.
Einstein's view of the Universe seemed to go against common sense, but that was only because the average person deals with a Universe of small distances and small velocities. Under those conditions, Newton's theories hold almost perfectly. In fact, Einstein's equations reduce to Newton's under such conditions. However, where large distances and large velocities are involved, Einstein's equations hold and Newton's do not.
In the eight decades since special relativity was advanced, endless tests and observations have upheld it completely. No divergences between reality and the Einsteinian view have been found.
pMessages From the Heart
1903 AD
DENMARK
That muscles gave rise to tiny electric potentials had been known since Italian anatomist Luigi Galvani's (1737-1798) time. It seemed natural to suppose, then, that the heart, beating rhythmically, might give rise to rhythmic electric potentials. Perhaps a departure from the natural rhythm might be used to diagnose pathological conditions before they could be discovered in any other way. The problem was to detect the small currents with sufficient accuracy.
In 1903 a Dutch physiologist, Willem Einthoven (1860-1927), developed the first string galvanometer. This consisted of a delicate conducting thread stretched across a magnetic field. A current flowing through the thread would cause it to deviate at right angles to the direction of the magnetic lines of force. The delicacy of the device was sufficient to make it possible to record the varying electrical potentials of the heart.
The result was an electrocardiogram. The abbreviation is EKG because in German "cardio" is spelled with a k. For the development of electrocardiography, Einthoven was awarded the Nobel Prize for medicine and physiology in 1924.
_Electricity In, Motion Out
1831 AD
NEW JERSEY
American physicist Joseph Henry (1797-1878) discovered electrical induction in 1823 independently of English physicist Michael Faraday (1791-1867), but the latter published first by a few months and gets the credit. Henry went on to study the reverse process. If the rotary motion of a copper wheel cutting across magnetic lines of force can induce an electric current, then an electric current ought to be able to produce a rotary motion.
In essence, Faraday had already shown this in a simple way), but in 1831 Henry devised a much more practical version of such a machine, one in which a wheel would turn if electric current was supplied. This was the first practical electric motor (from a Latin word meaning "to move").
The importance of the motor cannot be overemphasized. A motor can be made as large or as small as desired. It can be run by electricity brought to it over a distance of many miles. Most important of all, it can (unlike a steam engine) be started in a moment and stopped in a moment.
The supply of cheap, abundant electricity made possible by Faraday's discovery of the generator (once it was sufficiently improved) would have been useless without some means of putting it conveniently to work. Henry's motor (once it was sufficiently improved) did that, so that between them, Faraday and Henry ushered in the age of electricity.
─Embryo: A Look at Life
1973 AD
STOCKHOLM, SWEDEN
People have always been able to see much of the world around them, and even -- by examining dead people -- to observe the interior structure of the human body.
But it is only recently that optical and surgical equipment has been developed that allow us to watch the interior of the body in action. In this picture we see one of the most amazing aspects of life, the development of a human being in its mother's womb.
Because human beings are born all the time, we sometimes forget how amazing this process is.
The life process starts when two half-cells -- one half from the mother and the other half from the father -- join together into one full-cell.
Though this cell is so tiny you couldn't see it without a microscope, it contains an astonishing amount of information. The entire design for a person, a being more complicated than anything people have ever designed, is contained in just the smallest part of the cell. This information chain (called "DNA," for deoxyribonucleic acid) is so small that scientists can't see it with regular optical microscopes, so they use powerful electron microscopes. If computer designers could easily duplicate this information chain, they could build computers far more powerful than anything available today.
But this original cell not only contains all the information necessary to design a human body, but also has the ability to build the body. In other words, this little cell is not only like a giant library, but also like a factory that can reproduce itself!
Over nine months in the womb, the body grows. Within several weeks you can begin to recognize the head, then later you can see the arms and feet, and finally -- at birth -- the full body.
äENIAC: Not a Laptop
1946 AD
UNIVERSITY OF PENNSYLVANIA
American electrical engineer Vaannevar Bush (1890-1974) had devised a computer that made use of radio tubes as electronic switches in addition to the usual mechanical parts.
The obvious next step was to make an entirely electronic computer, with no moving mechanical parts at all. This was done by the American engineers John William Mauchly (1907-1980) and John Presper Eckart, Jr. (b. 1919), who devised the first practical electronic digital computer in 1946. It was called ENIAC (electronic numerical integrator and computer).
It was an enormous, energy-guzzling device, weighing 30 tons and taking up 1,500 square feet of space. Though it was a wonder of its time, ENIAC was retired some nine years after it had been set up. It was by then hopelessly obsolete, for its descendants were growing steadily smaller, cheaper, more efficient, and much more capable.
pFirst Trip Around the Moon
1968 AD
LUNAR ORBIT
On September 17, 1968, the Soviet probe Zond 5, with no crew aboard, circumnavigated the Moon. On December 24, 1968, the American probe Apollo 8, with three astronauts aboard -- Frank Borman (b. 1928), James A. Lovell, Jr. (b. 1928), and William A. Anders (b. 1933) -- circumnavigated the Moon ten times. The stage was finally set for a lunar landing.
2Great Seasons from Earth's Orbit
1920 AD
YUGOSLAVIA
Weather is so erratic that even the most modern devices have trouble predicting it long in advance. Nevertheless, very general cycles of weather may exist, and these may explain the periodic ice ages that have occurred in the last million years of Earth's history.
In 1920 the Yugoslavian physicist Milutin Milankovich (1879-1958) suggested that astronomic factors played a part. Slow oscillations in the eccentricity of Earth's orbit and in the tilting of the Earth's axis, together with the precession of that axis, seemed to suggest a 40,000-year cycle, which could be divided into a Great Spring, Great Summer, Great Autumn, and Great Winter, each about 10,000 years long.
Milankovich's suggestion was ignored at the time, but after more than half a century, it came to be considered seriously.
^Europe: A Bright Setting Sun
1990 AD
On ancient Assyrian monuments are some of the earliest references to Europe and Asia. In contrast to "Asu" (Asia), which means "Land of the rising sun," "Ereb" (Europe) means "land of darkness," or "land of the setting sun."
Despite that rather dismal description, Europe has actually had many bright days in science, art and government.
Europe is the land area located north of the Mediterranean Sea and west of the Ural Mountains in Soviet Union. Its culture owes much of its character to two major forces: the Greeks and the Romans.
From the sixth and fourth centuries BC, the seagoing Greeks spread their arts and sciences throughout the Mediterranean basin. Then the Romans adopted it and spread it to places the Greeks had barely touched. But the Romans also added much, including their own versatile language, Latin, and their expertise in government and law. Even with the fall of the Roman Empire, much Roman civilization survived through the Roman Catholic Church.
Even today, much art and science is built on Greek foundations, and much law and government is based on the Roman model.
ñInvisible Glasses
1854 AD
GERMANY
For some six centuries, people who were nearsighted, farsighted, or astigmatic had worn spectacles, or eyeglasses, to correct their vision.
Eyeglasses, however, are a noticeable adjunct that call attention to a physical shortcoming. Furthermore, the myth arose that men who wore glasses were effeminate and that women who wore them were ugly. (The movies, in particular, helped propagate these mischievous ideas.) For that reason, it seemed useful to correct vision in a less conspicuous way.
As early as 1887, a German physician, Adolf Eugen Fick (1829-1901), had worked out the notion of contact lenses, small lenses that would just fit over the iris of the eye, correcting vision without anyone noticing it.
Glass in direct contact with the eye, however, would be irritating and dangerous. In 1954 plastic contact lenses were produced, which proved useful and popular, and contact lenses are now in common use.
ΓThe Cold Squeeze
1823 AD
LONDON, ENGLAND
Generally speaking, there are two ways of making a gas condense into a liquid. You can cool it. This deprives the gas of energy, and its molecules sink toward each other and cling together. You can also put it under pressure. This forces the molecules toward each other until they cling. Naturally, if you use cold and pressure, you do better still.
English physicist Michael Faraday (1791-1867) was the first to use cold and pressure in a systematic attempt to liquefy gases. He used a strong glass tube bent into a boomerang shape. In the closed bottom, he placed some substance that, when heated, would liberate the gas he was trying to liquefy. He then sealed the open end. He placed the bottom end in hot water. This liberated the gas in greater and greater quantities and, since the gas was in the limited space within the tube, it developed greater and greater pressure.
The other end of the tube Faraday kept in a beaker filled with crushed ice. At that end the gas would be subjected to both high pressure and low temperature and would liquefy. In 1823 Faraday liquefied the gas chlorine in this manner. (Chlorine's normal liquefaction point is -34° C.) Using this method, Faraday liquefied several other gases, too.
YHyping Up Protons
1929 AD
UNITED KINGDOM
In the quarter-century since the discovery of radioactivity, the most energetic particles easily available to nuclear physicists had been alpha particles. The shorter the half-life of a particular radioactive isotope, the more energetic the alpha particles they produced. In 1906 British physicist Ernest Rutherford (1871-1937) used alpha particles to bombard atoms and induce nuclear reactions, but even the most energetic alpha particles could only do so much. Of course, cosmic ray particles were more powerful still, much more powerful, but they were not under scientists' control.
What was needed was some way of beginning with ordinary nuclear particles, say protons obtained by ionizing hydrogen atoms, and then accelerating them, perhaps by means of an electromagnetic field.
This was first accomplished by the British physicist John Douglas Cockcroft (1897-1967) and his coworker, the Irish physicist Ernest Thomas Sinton Walton (b. 1903). In 1929 they devised a voltage multiplier that would build up high electrical voltages capable of accelerating protons to the point where they contained more energy than the alpha particles occurring in nature. This was the first particle accelerator (better known to the public for a time as an atom-smasher). For this work, Cockcroft and Walton were awarded the Nobel Prize for physics in 1951.
Strange & Charmed; Quark Twins
1974 AD
BROOKHAVEN NATIONAL LAB, NEW YORK
While there may be only twelve leptons, there are a large number of hadrons, beginning with the pion, which is the least massive hadron, through over a hundred more massive ones.
Leptons, however, are fundamental particles, which cannot be broken down into simpler ones (as far as we now know), while hadrons are composite particles and are made up of quarks. Quarks, like leptons, seem to be fundamental particles.
In 1974 three kinds of quarks were known: u-quarks, d-quarks, and s-quarks. (The letters stand for up, down, and strange, respectively, though sometimes the s is made to stand for sideways to match the other two.) However, theoretical considerations indicated that quarks ought to exist in pairs. Up-quarks and down-quarks were a pair; there ought to be a quark to serve as the pair of the strange-quark. Such a new quark was named a c-quark even before it was discovered, the c standing for charmed.
In 1974 the American physicist Burton Richter (b. 1931), using the enormous energies of the latest particle accelerators, produced a particle that, from its properties, had to include a c-quark in its makeup. Another American physicist, Samuel Chao Chung Ting (b. 1936), working independently, also produced a particle that had to contain a c-quark. The two shared the Nobel Prize for physics in 1976.
A third pair of quarks, the t-quark and the b-quark (which may stand for top and bottom, or for truth and beauty, depending on the level of whimsy), undoubtedly exist also. If so, there are twelve quarks (the ones I've mentioned and their antiparticles) to match the twelve leptons. This may be significant, though no one yet can explain why quarks and leptons should match each other in number, or why that number should be twelve.
╞Light Conversation
1970 AD
LONDON, ENGLAND
Since current electricity had come into use metallic wires, especially those of copper, had been used to conduct the current wherever it was needed.
By 1970 techniques had been developed to conduct light by means of fine, very clear glass fibers. The fibers were coated with plastic or with a second type of glass so chosen that any light that tended to travel out of the fiber into the coating would be totally reflected. In this way, light could follow the fiber around curves and corners. With the use of lasers, such light could be as easily modulated as electric currents, so that sound waves could be converted into light of varying amplitude and, at the other end, reconverted into sound waves.
Fiber optics, by replacing expensive copper with cheap glass and by using the tiny waves of light, which can carry enormous amounts of information, was instantly seen as having the potential of greatly extending communication by telephone.
wUnited We Calculate
1960 AD
DALLAS, TEXAS
Transistors had been in existence for a dozen years, constantly being made smaller and more reliable. By 1960 they could be made so small that it made no sense to try to handle them as separate units.
Instead, small pieces of thin silicon or some other semiconductor, about a quarter-inch square, were etched with tiny transistor circuits. These chips did the work of many transistors and were called integrated circuits.
The use of integrated circuits made computers smaller, cheaper, and more versatile. As time went on, more and more circuits -- eventually thousands -- could be etched into a single chip.
≈Drosophila Make Research Fly
1907 AD
NEW YORK, NEW YORK
In 1865 Austrian botanist and Augustinian monk, Gregor Johann Mendel (1822-1844), had worked out the laws of inheritance by studying pea plants, and in 1902 these laws had been verified for animals by British biologist William Bateson (1861-1926). However, animals are much harder to work with on the whole than plants are. In 1907, however, the American geneticist Thomas Hunt Morgan (1866-1945) began to use a tiny insect called Drosophila, or fruit fly. They have only four chromosome pairs in each cell, are simple to feed, and breed readily and copiously at brief intervals.
In studying them, Morgan found that there were characteristics that were linked and inherited together, but that the linkage was not necessarily permanent. Every once in a while, two characteristics that had previously been inherited together were suddenly inherited independently. He was able to correlate this with the fact that chromosomes sometimes interchanged parts so that two characteristics ordinarily on the same chromosome came to be on different chromosomes.
Fruit fly research greatly hastened the pace at which knowledge of genetic mechanisms increased. For his work with them, Morgan was awarded the Nobel Prize for medicine and physiology in 1933.
░No Two the Same
1885 AD
ENGLAND
In 1885 British anthropologist Francis Galton (1822-1911) pointed out the individuality of fingerprints. No two people (barring identical twins) had identical fingerprints, and Galton worked out a thoroughgoing system of classifying and identifying them.
In handling smooth surfaces, people always left sweaty, greasy fingerprints, even when these were unnoticeable unless the surface was appropriately powdered.
Eventually, fingerprints proved a useful way of showing that a given person had been present at a given place and had handled a given object. This added a new dimension to forensic medicine (from a Latin word referring to a public place such as a courtroom).
Never Ending Fractions
1586 AD
NETHERLANDS
Mathematicians had found fractions difficult to handle ever since the days of the Sumerians. Special rules had to be worked out to deal with them.
In 1586, however, Dutch Mathematician Simon Stevin (1548-1620) showed that they could be made part of ordinary positional notation. To the right of the units column (on the other side of a decimal point) could be the tenths column, then the hundredths column, and so on. Thus 2-1/4 would become 2.25; 2-1/8 would become 2.125; 2- 7/8 would become 2.875; and so on.
The disadvantage of such decimal fractions is that some never end.
Thus 2-1/3 is 2.3333333 . . . forever; 2-5/6 is 2.8333333 . . . forever; and so on. Despite this, decimal fractions greatly simplified computations involving fractions.
aFranklin's Shocking Discovery!
1752 AD
PHILADELPHIA, PENNSYLVANIA
The Leyden jar had become a favorite plaything of many scientists. One of them was Benjamin Franklin.
In 1747 Franklin rejected French physicist Charles-Françcois de Cisternay du Fay's notion of two electrical fluids. He thought there was only one, which could exist in an excess (above normal) or in a deficiency (below normal). Excess repelled excess, since neither could accept the other's. Similarly, deficiency repelled deficiency, since neither could offer anything to the other. Excess, however, attracted deficiency, and the electrical fluid poured from the excess to the deficiency, neutralizing both and leaving each uncharged.
Franklin suggested that the excess be called positive electricity and the deficiency negative electricity. There was no telling which variety of electricity, vitreous or resinous, was positive and which negative. Franklin guessed arbitrarily and happened to guess wrong. That makes no difference, however. The names can be used and the literal meanings forgotten.
Franklin noted the manner of discharge of the Leyden jar. When the electrical charge was drawn off, it emitted a spark of light and a crackle of sound. Franklin was struck by the similarity to a tiny lightning stroke and an equally tiny crack of thunder. He at once reversed the thought. During a thunderstorm, did Earth and sky set up a gigantic Leyden jar, and was the lightning and thunder an equally gigantic discharge?
He decided to experiment. In 1751, he flew a kite in a thunderstorm. The kite carried a metal point to which a long silk thread was attached. At the bottom of the thread, near Franklin (who held onto the silk by way of a second thread that remained dry), was a metal key. As the thunderclouds gathered and the silk thread began to show signs of electrical charge (the separate fibers repelled each other), Franklin put his knuckle near the key and it sparked and crackled just like a Leyden jar. Moreover, Franklin charged a Leyden jar from the key just as easily as if it were a friction machine. The Leyden jar charged by heavenly electricity behaved precisely as though it had been charged by earthly electricity. The two electricities were identical.
Franklin was able to put his discovery to practical use at once. Lightning, he decided, hit a particular building when that building gathered charge during a thunderstorm. His experience with Leyden jars showed that they discharged much more easily if a sharp needle was attached to them. Indeed, the charge leaked out so easily through the needle that they couldn't be charged in the first place. Why not, then, attach a sharp metal rod to the top of a building, and ground it properly, so that any charge that gathered might leak away rapidly and silently and no charge would accumulate to the point where a disastrous discharge would be forced.
Franklin published his thoughts on the matter in 1752 in Poor Richard's Almanac, and the lightning rods, as they were called, began to go up at once, first in America and then in Europe. They proved efficacious, and for the first time in history, a natural catastrophe was averted not by prayer or by magical incantations of one sort or another, but by reliance on an understanding of natural laws. Once lightning rods appeared on church steeples (which, being the highest point in town, were particularly vulnerable), the point was made for all to see.
ëCatching People Off Guard
1893 AD
VIENNA, AUSTRIA
Austrian physician Josef Breuer (1842-1925) had started to use hypnotism in the treatment of mental diseases such as hysteria. The method had later been taken up by Austrian physician Sigmund Freud (1856-1939), but he eventually abandoned hypnotism for free association, allowing the patient to talk randomly and at will with a minimum of guidance. In this fashion, the patient was gradually put off guard, and matters came to be revealed that in ordinary circumstances would have been kept secret from the patient's conscious mind.
The advantage of this method over hypnotism was that the patient was aware of what was going on at all times and did not have to be informed afterward of what had been said.
In 1893 Freud and Breuer published The Psychic Mechanism of Hysterical Phenomena. This is considered to have laid the foundations of the medical technique of psychoanalysis.
Fuel Cell: Laboratory Curiosity
1839 AD
UNITED KINGDOM
Ordinary electric batteries, even the copper and zinc Daniell cell developed by British chemist John Frederic Daniell (1790-1845), obtain their energy by, in effect, burning metals. Electricity, as obtained from batteries, would be much cheaper if ordinary fuels could be burned instead, a fuel cell.
In 1839 the British physicist William Robert Grove (1811-1896) devised an electric cell that made use of hydrogen and oxygen, producing electricity as they combined into water. Even today hydrogen is still rather expensive, however. Using methane or coal dust along with oxygen would be close to ideal, but in all the century and a half since Grove's discovery, scientists have not been able to make the fuel cell practical. It remains a laboratory curiosity.
RNew York-Albany: Just 32 Hours
1807 AD
NEW YORK, NEW YORK
Since American inventor John Fitch (1743-1798) failed to make his steamboat succeed, the notion had not been taken up again. But then the American inventor Robert Fulton (1765-1815) tackled the project. In 1807 he built the Clermont, 133 feet long. This vessel performed well, steaming up the Hudson from New York to Albany in 32 hours, maintaining an average speed of nearly 5 miles per hour.
Soon he had a fleet of steamboats in operation, and unlike Fitch, he was commercially successful. For this reason, Fulton is usually considered the inventor of the steamboat.
öHerschel Counts Stars
1785 AD
BATH, UNITED KINGDOM
British astronomer William Herschel (1738-1822) reported in 1785 on his attempt to determine the shape of the conglomeration of stars of which we were part. To count all the stars all over the sky was, of course, impractical. He therefore took samples. He chose 683 regions, well scattered, and counted the stars he could see in each one. (This was the first application of statistical methods to astronomy.)
He found that the number of stars per unit area of sky rose steadily as one approached the Milky Way, was maximal in the plane of the Milky Way, and minimal in the direction at right angles to that plane. This, he thought, would be explained if the star system were lens-shaped, with the Milky Way marking out the long diameter of the lens all around.
Such a lens-shaped star collection had been supposed by earlier astronomers, but Herschel had now made it a matter of close observation. For the first time, the Galaxy truly took shape, although even then no astronomer had a conception of its true size or of the vast number of stars it contained. Herschel thought it contained a hundred million stars -- an enormous underestimate.
╞Galileo: Sarcastic but Right
1633 AD
ROME, ITALY
Galileo Galilei (1564-1642) had long accepted the Copernican idea of a heliocentric planetary system, but he was reluctant to be open in this view, for the papacy was strong in Italy and geocentrism was the only allowable astronomical view in Catholic doctrine of the time.
Urban VIII (1568-1644) had become Pope in 1623, and Galileo thought him to be a friend. In 1632, therefore, he took the chance of publishing a book with the title, in English, Dialogue on the Two Chief World Systems. The dialogue has three actors: a Ptolemy-supporter, a Copernicus-supporter, and a neutral person seeking information.
The book created a stir. In the first place, it was written in Italian rather than in Latin, so that it was not confined to scholars but could reach the general public. In the second place, Galileo was a brilliant writer, much given to sarcasm, and he certainly gave the Copernican the best of it. What's more, it was easy to persuade the Pope that the Ptolemy-supporter was meant to be a satire on him personally.
Galileo was therefore brought before the Inquisition in the most famous confrontation between science and religion prior to the evolution controversy in the present century.
On June 22, 1633, under the threat (but not the use) of torture, he was forced to renounce any of his views that were at variance with geocentrism. Sometimes Galileo is blamed for giving in, but he was seventy at the time, and he had the example of Italian philosopher Giordano Bruno (1548-1600), a generation before, to keep in mind.
However, the victory of the Church was an empty one. The heliocentric theory continued to gain an ever-firmer hold on the minds of scientists and ordinary people everywhere.
φJumping Frog Legs!
1780 AD
ITALY
An Italian anatomist, Luigi Galvani (1737-1798), noticed in 1780 that the muscles of dissected frog legs twitched wildly when a spark from a Leyden jar struck them. This was not too surprising. Electric shocks made living muscles twitch, why not dead ones, too?
Since Benjamin Franklin (1706-1790) had shown that lightning was electrical in nature, Galvani wondered whether muscles would twitch if exposed to a thunderstorm. He therefore placed frog muscles on brass hooks outside the window so that they rested against an iron latticework.
The muscles did indeed twitch during the thunderstorm, but they also twitched in the absence of it. In fact, they twitched whenever they made simultaneous contact with two different metals.
Apparently, electricity was involved, but where did it come from, the metals or the muscle? Galvani decided it was the muscle, and he spoke of animal electricity. In this he was wrong, but electricity was involved with nerve and muscle action just the same.
Link-Up In Space
1985 AD
EARTH ORBIT
Maneuverability in space was increasing rapidly. On December 15, 1965, the American satellite Gemini VII, having been in space for fourteen days, approached within several feet of the previously launched Gemini VI. This was the first space rendezvous.
On March 16, the American satellite Gemini VIII linked up with another orbiting vessel. This was the first actual docking of one space vessel with another -- a maneuver essential if human beings were to be sent to the Moon and brought safely back.
QMaking New People?
1973 AD
UNIVERSITY OF COLORADO
It is one thing to understand the fundamental chemistry of the DNA molecules that make up the genes; it is another to be able to modify that chemistry. In 1973 two American biochemists, Stanley H. Cohen and Herbert W. Boyer, showed that when DNA was broken into fragments and these were combined into new genes, the new genes could be inserted into bacterial cells, where they could be reproduced whenever the cells divided in two.
This was the beginning of genetic engineering. It offered a technique for something as simple and useful as modifying defective genes to make them normal, thus holding out the hope that genetic defects might someday be cured. It also offered the possibility of something as far-reaching as the ability to direct human evolution (with all the treacherous side effects that might involve).
▒ Mendel's Pea Plants
1865 AD
BRNO, CZECHOSLOVAKIA
There was a flaw in the theory of evolution proposed by British biologist Charles Robert Darwin (1809-1882) in 1858. Granted that in every generation of a particular species there are random variations, there are also (to some extent, at least) random matings. Therefore, the variations should tend to vanish into an average, since extremes are not likely to mate with similar extremes. (It might even be argued that the second law of thermodynamics requires this tending toward an average.)
The flaw was addressed by an Austrian botanist and Augustinian monk, Gregor Johann Mendel (1822-1884), who experimented with peas that he grew in the monastery garden.
Carefully, Mendel arranged for various plants to self-pollinate, wrapping them to guard against accidental pollination by insects. Carefully, he saved the seeds produced by each self-pollinated plant, planted them separately, and studied the new generation.
Mendel found that if he planted seeds from dwarf pea plants, only dwarf pea plants sprouted. The seeds produced by this second generation also produced only dwarf pea plants. The dwarf pea plants "bred true."
Seeds from tall pea plants behaved in a more complicated fashion. Some bred true, but some did not. Those that did not breed true gave rise to tall plants three-quarters of the time and to dwarf plants one-quarter of the time.
Mendel then crossed dwarf pea plants with the tall pea plants that bred true. All the peas produced grew into tall pea plants. The characteristics of dwarfness seemed to have disappeared.
Next Mendel had each of this new generation of tall plants self-pollinate and found that they produced peas that grew into tall plants and dwarf plants in a 3-to-1 ratio. Dwarfness had been submerged in one generation but had then shown up in the next.
In other words, tallness was dominant and dwarfness recessive, so that tallness overwhelmed dwarfness -- but only temporarily.
Mendel found that other types of traits in pea plants worked the same way. There was no mixing of extremes.
Mendel also found that male and female contributed equally. It was as though each organism had two factors for a particular trait and each contributed one of them to the offspring. If the factors were different in the offspring, and one was dominant, the recessive characteristic didn't show but was still there. It might be the one handed on to the next generation, and if the other parent also handed on a recessive, so that the offspring had two recessives and no dominant, the recessive trait would appear again.
Mendel thus worked out the Mendelian laws of inheritance, as they were later to be called, and founded the science of genetics (from a Greek word meaning "to give birth to"). He published his first paper on this work in 1865 (a second followed in 1869), but it was totally ignored for thirty-three years.
Since the Mendelian laws showed that extremes did not mix into a blind average, but continued to show up, they provided the mechanism by which natural selection could bring about a gradual change in species. Thus, Mendel corrected the flaw in Darwin, but both Mendel and Darwin were dead before the world of science came to realize what had happened.
u
Geometry: Proof Upon Proof
300 BC
ALEXANDRIA, EGYPT
Geometry, as a practical study, may have begun in Egypt, where the building of pyramids and the necessity of reestablishing boundaries after the Nile flood made it essential. The Greeks made it theoretical, however, working with ideal points, lines, curves, planes, and solids. They attempted to prove things by reason alone and without actual measurement. (Reason was the mark of the philosopher, measurement was only for the artisan, and the Greek scholars were snobs. Snobbery turned out to be useful in mathematics, though not in experimental science, where the Greeks fell badly short.)
A number of Greek mathematicians contributed to the development of geometry, particularly Eudoxus. It was Euclid (fl. ca. 300 B.C.) who brought geometry to maturity, however. He worked in Alexandria, Egypt, and thereby hangs a tale.
The city of Alexandria, on the seacoast at the westernmost branch of the Nile delta, had been founded by Alexander the Great (356-323 BC) and named after himself. It was a largely Greek city, though it contained many Egyptians and Jews as well. It quickly became the largest and most cosmopolitan city of the Greek world. Ptolemy I (ca. 366-ca. 283 B.C.), who ruled over Egypt after Alexander's death, established his capital at Alexandria.
Ptolemy I saw himself as a patron of the arts and sciences and founded the Museum, so-called because it was an institution devoted to the Muses, the patron goddesses of learning. He and his son, Ptolemy II (308-246 B.C.), made the Museum the largest and most important of all the ancient universities. Associated with it was the largest of all the ancient libraries. The Ptolemies encouraged scientists and thinkers generally to come to Alexandria and subsidized them well. Euclid, a Greek mathematician who may have studied at the Academy, moved from Athens to Alexandria as a result, symbolizing the "brain drain" that followed, as Greeks poured out of Greece proper into the new dominions of the Hellenistic kingdoms that succeeded Alexandria. Perhaps about 300 B.C., Euclid began compiling all the geometrical findings of earlier mathematicians into a textbook eventually called Elements. He added comparatively little himself, but what he did was beyond price.
He began with a minimum number of statements that were so self-evident that they required no proof. From these axioms, he proceeded systematically to prove theorem after theorem, each proof depending only on the axioms and on previous proofs, so that geometry was given a firm foundation and structure. It was the most successful textbook ever written and has been used, in more or less modified form, to this day.
YGiotto's Realistic Comet
1301 AD
ITALY
A bright comet was visible in Europe's sky in 1301. It created the usual panicky stir, but the Italian artist Giotto di Bondone (ca. 1267-1337), usually known by his first name, observed it with an artist's eye.
Till then, and for a considerable time afterward, those who drew comets let their panic be their guide and presented the silliest pictures imaginable. In 1304, however, Giotto painted The Adoration of the Magi, in which he pictured the star of Bethlehem as a comet, and seems to have let the comet of 1301 guide his brush. Giotto's is the first realistic depiction of a comet.
yThe Dream of Flying
1809 AD
UNITED KINGDOM
The dream of active flight had exercised the human imagination for millennia.
Usually, however, human beings could only think of imitating the birds. The Greek myth of Daedalus had that legendary inventor building a frame to which he stuck feathers in wax and which he moved in birdlike fashion with his arms.
The first person to consider the principles that would really keep objects in the air was a British scientist, George Cayley (1773-1857). He visualized flying devices with fixed wings that presented appropriate surfaces to the air, tails with control surfaces to allow turning and braking, and propulsive mechanisms. He described all this in publications that began to appear in 1809.
In these he founded the science of aerodynamics. While the state of technology at that time did not allow the construction of such devices, when they did come a century later, they fulfilled Cayley's requirements.
Balloons had been in existence for seventy years, proving that objects that were themselves denser than air could remain aloft under proper conditions of winds and updrafts, but Cayley was the first to study, scientifically, the conditions under which air might keep a heavier-than- air object aloft. He thus founded the science of aerodynamics. He realized that what was needed were fixed wings, like the flaps of a flying squirrel, rather than moving wings, like those of birds.
He worked out the basic shape that airplanes would eventually have -- wings, tail, streamlined fuselage, and rudder. He also realized that he needed an engine and propeller to be able to proceed against the wind, but he knew that no engine then existing would be light and powerful enough to do so.
In 1853 he built the first device so constructed aerodynamically as to glide with the wind and lift with the updrafts -- a glider, as it came to be called. Cayley, too old to take the risk, ordered his coachman to take the first glider flight. The coachman did so, vehemently objecting, flew 500 yards, and survived. Over the second half of the nineteenth century, glider-flying became a popular sport, as balloon-flying had been in the first half.
(Whoops! Vulcanized Rubber
1839 AD
UNITED STATES
Rubber had come to the attention of Europeans when explorers found Native Americans using it. It was obtained from the sap of a tree originally native to tropical America but since grown in southeastern Asia and in other places as well.
Rubber was recognized as a useful waterproofing material, since it was impervious to water and wasn't rotted by it either. The trouble was, though, that when it grew cold, it stiffened and became brittle, and when it grew hot, it became soft and sticky. Attempts were made to find ways of making rubber less sensitive to temperature change, but at first there was only failure.
Then, in 1839, the American inventor Charles Goodyear (1800-1860) had a stroke of luck. He was trying to add sulfur to rubber when some of the mixture came accidentally into contact with a hot stove. To Goodyear's astonishment, those portions that weren't scorched too badly became dry and flexible, and they didn't lose flexibility in the cold or dryness in the heat. He began to heat the rubber-sulfur mixture to higher temperatures than anyone else had tried and thus obtained vulcanized rubber (after Vulcan, the Roman god of fire).
It was only with this discovery that rubber became truly useful, far more useful eventually than anyone might have suspected in Goodyear's day.
^Fire on Water
673 AD
CONSTANTINOPLE
The Arabs, emerging from their peninsula in 632 B.C., began an amazing series of conquests that in the space of fifty years seemed to bring to life again the old Persian Empire with Arabia and North Africa added. Nothing more seemed needed but the city of Constantinople itself before all the European dominions of the old Roman Empire would fall. In 673 the Arab army was just across the Hellespont from Constantinople, and their fleet was offshore. It seemed that nothing could possibly save the city.
There was in the city, however, an alchemist named Callinicus (7th century), of Egyptian or Syrian birth, who had arrived in Constantinople as a refugee. He had invented a mixture containing naphtha, plus potassium nitrate and calcium oxide, perhaps (we don't know the exact recipe), which not only burned but would continue to burn on water even more fiercely. This Greek fire was spurted out of pipes into the paths of the wooden ships of the Arabs. The fear of being set on fire, and the horror of watching fire burn on water, forced the Arab fleet to retreat and Constantinople was saved.
WGreenhouse Earth?
1988 AD
EARTH
It had been known since 1884, when Swedish chemistry student Svante August Arrhenius (1859-1927) had pointed it out, that carbon dioxide in the atmosphere acted as a heat trap, making Earth's temperature warmer than it would otherwise be. (This was called the greenhouse effect.)
It was also known that the carbon dioxide content of the atmosphere had been rising steadily since 1900, partly because of the increasing use of coal and oil, which produce carbon dioxide when burned, and partly because of the cutting down of forests, which are the most efficient consumers of carbon dioxide.
As it happened, 1987 was the warmest year yet recorded by weather bureaus, and 1988 was warmer still. What's more, 1988 saw disastrous droughts in the United States and elsewhere. There was a feeling that the greenhouse effect was intensifying, and world concern began to intensify accordingly.
Rising temperatures would not only alter Earth's climate (probably for the worse) but could promote the melting of Earth's ice caps to produce a disastrous rise in sea level of up to 200 feet. The greenhouse effect, plus the thinning of the ozone layer, the steady rise in environmental pollution, and the inexorable increase in population, seemed to have placed the very habitability of our planet at risk, and a sense of crisis was beginning to pervade the world.
╞The Great Lakes Hub
1990 AD
Below you are the Great Lakes of the United States and Canada. The border between the United States and Canada runs down the middle of Lake Superior, a giant body of water larger than several states.
To the right of Lake Superior are lakes Michigan, Huron, Erie and Ontario.
At the south tip of Lake Michigan is the city of Chicago, Illinois, a communications center through which roads, railroads, airports serve the midwestern United States.
ÖThe Properties of Nothing
1645 AD
GERMANY
Once Italian physicist Evangelista Torricelli (1608-1647) had produced a vacuum by allowing mercury to pour out of a tube, it seemed to some that vacuums could be produced in more direct ways. Perhaps air could simply be pumped out of any vessel, and larger volumes of vacuum could be formed than Torricelli had managed.
A German physicist, Otto von Guericke (1602-1686), produced the first practical air pump in 1645. It worked like a water pump but with parts sufficiently well fitted to be reasonably airtight. It was run by muscle power and was slow, but it worked. Guericke produced a large enough vacuum to make useful experiments possible.
He was able to show that a ringing bell within a vacuum could not be heard, thus bearing out Aristotle's contention that sound would not travel through a vacuum. Guericke also showed that candles could not burn in a vacuum and that animals could not live.
He also weighed a metal sphere before he evacuated it and then again afterward. The small loss in weight was obviously the weight of air that had been inside. From that, and the volume of the air, he was able to get the first measurement of air's density.
ª Gutenberg's Movable Type
1454 AD
GERMANY
There is no way to overestimate the importance of writing. Nevertheless, it can't be denied that writing is a tedious process, and there have always been efforts to hasten it. The Egyptians worked out faster ways of scrawling their complicated symbols, and the Romans worked out systems of shorthand.
The ancient Sumerians, however, developed little cylinders of hard stone with designs incised into them that could be rolled onto soft clay so that the designs were impressed, and these could be made permanent by baking. The cylinders could be used over and over again and served as a signature for the owner.
Why could not the same system be used for pressing symbols onto a sheet of paper? If a block with a raised reversed symbol on it is smeared with ink, it can press an inked symbol (nonreversed) onto paper. The Chinese started doing this about the year 350, and by 800 they were carving entire pages on wooden blocks. Such a page could then be printed any number of times, all the impressions being exactly alike. But then, it took a long time to carve the wooden block into a bas-relief with all the symbols perfectly formed.
Later the Chinese got the idea of using a different block for each symbol, so that the blocks could be arranged into any desired combination to give any desired page. By 1450 they had movable wooden characters of this type, and by 1500 they were making use of metal characters.
By then, though, the Europeans had out-stripped them (though it is possible that news concerning movable type had reached Europe from China and given the Europeans a head start).
The German inventor Johannes Gutenberg (ca. 1390-1468) had been working out the matter of movable type since 1435. He had paper to work with (it had long ago reached Europe from China) and he experimented with different inks. He also designed a printing press, a device that would press the paper down on all those little metal characters evenly.
By 1454 Gutenberg had worked out all the bugs in his process and was ready for the big task: he began to put out a Bible, in double columns, with forty-two Latin lines to the column. He produced three hundred copies of each of 1282 pages and that produced the three hundred Gutenberg Bibles. It was the first printed book, and many people consider it the most beautiful ever produced -- so that the art was born at its height. The Gutenberg Bibles that remain today are the most valued books in the world.
ⁿMontgolfiers' Flying Zoo
1783 AD
PARIS, FRANCE
Light objects can be borne on the air, as all of us observe in the case of small feathers, dandelion seeds, and so on. If objects are light enough, they needn't depend on wind and updrafts to remain in the air (or on muscular power as in the case of birds, bats, and insects). A light enough object can actually float in air, just as wood floats on water.
There are no known solids or liquids that are lighter than air, but some gases are. It occurred to two French brothers, Joseph-Michel Montgolfier (1740-1810) and Jacques-Étienne Montgolfier (1745-1799), that hot air expanded and was therefore lighter than an equal volume of cold air. If a quantity of hot air filled a light balloon, the hot air would float in the air and might have enough upward push to carry the balloon with it. In fact, if the balloon was large enough, there might be sufficient buoyancy to carry a human being upward.
On June 5, 1783, in the marketplace of their hometown, the brothers filled a large linen bag, 35 feet in diameter, with hot air. It lifted 1,500 feet upward and floated a distance of a mile and a half in 10 minutes. They went to Paris, and on September 19, they managed a flight of 6 miles before a crowd of three hundred thousand that included Benjamin Franklin.
The balloon carried up not only itself but a wicker basket in which were a rooster, a duck, and a sheep, which were not harmed. Finally, on November 20, a hot-air balloon carried into the air a French physicist, Jean Françcois Pilatre de Rozier (1756-1783), and a companion. They were the first aeronauts in history.
Meanwhile, a French physicist, Jacques-Alexandre-César Charles (1746-1823), having heard of the hot-air balloons, realized that hot air had comparatively little buoyancy and lost that little as it cooled, though a fire in the basket underneath might suffice to keep it warm for a while. The gas hydrogen, studied by British chemist Henry Cavendish (1731-1810), was much lighter than hot air and had much greater buoyancy. What's more, the buoyancy was permanent. On August 27, 1783, Charles constructed the first hydrogen balloon and subsequently used one to rise nearly 2 miles in the air.
In subsequent decades, ballooning became almost a craze, and it was also used for scientific purposes.
≈First Drawing of Earth at Center
1507 AD
CRACOW, POLAND
The speculations of Aristarchus (fl. ca. 270 B.C.) in about 280 B.C. about a heliocentric system in which the Sun was at the center of the Universe, with the planets, including the Earth, revolving about it, had been disregarded, and the geocentric system of Hipparchus (fl. 146-127 B.C.) and Ptolemy (2nd century) had been accepted without question.
However, the mathematics needed to work out the planetary motions on a geocentric basis was very difficult. While the Sun and Moon moved steadily west- to-east against the stars, the other planets occasionally reversed direction (retrograde motion) and grew markedly brighter and dimmer as they progressed across the sky.
The Polish astronomer Nicolaus Copernicus (1473-1543) thought, as early as 1507, that if one went back to Aristarchus's view and supposed that all the planets, including Earth, were moving about the Sun, it would become easy to explain retrograde motion. It would also be easy to explain why Venus and Mercury always remained near the Sun and why planets grew dimmer and brighter. In addition to all this, the mathematics for working out planetary motions and positions would be simplified.
Copernicus did not, in his suggestions, abandon all Greek ideas. He clung to the notion that planets had to move in orbits that were circles and combinations of circles, and in this way he retained much unnecessary complexity.
The difference between Aristarchus and Copernicus was that Aristarchus merely presented his notion as a logical way of looking at the planets. Since others thought it wasn't logical, that ended it. Copernicus, however, used the Aristarchean idea to work out the actual mathematics of the planetary motions and show the reduction in complexity. This meant that even if people denied that the heliocentric system could be true, they would still be apt to use it as a simplified device for calculations.
Nevertheless, Copernicus hesitated to publish his theory and his computations, because he knew that the geocentric theory was approved by the Catholic Church. To advance a heliocentric theory would surely create a storm. He therefore quietly circulated his book only in manuscript form.
Finally he let himself be persuaded by enthusiastic friends to have the book printed. It was entitled De Revolutionibus Orbium Coelestium (Concerning the Revolution of Heavenly Bodies). He dedicated it to Pope Paul III (1468-1549) as a placatory gesture, and then died. The story is that Copernicus was given the very first copy of his book on the day of his death. As Copernicus had forseen, the book created a loud and violent storm. The Catholic Church put the book on its Index, forbidding the faithful to read it, and did not lift the ban till 1835. The Lutherans were equally hostile. The book could not be suppressed, however. With the coming of printing, far too many copies flooded the libraries of the scholars.
Copernicus's book totally overturned Greek astronomy, and though it was fifty years before astronomers generally could bear to turn their backs on Ptolemy and accept the fact that the vast Earth flew through space on an annual journey about the Sun, the book marked the birth of what came to be called the Scientific Revolution. With it came final proof that the ancients did not know it all and that moderns might strike out on their own in new directions and reach new heights -- and they certainly did.
It could be argued that just as printing made the Protestant Reformation possible, it also made the Scientific Revolution possible.
ÿThe Heroic Steam Engine
50 AD
ALEXANDRIA, EGYPT
Although Alexandria was now Roman and well past its great days, the Museum and the Library still existed, and a Greek engineer, Hero (1st century), worked there at about this time. Hero constructed a hollow sphere to which two bent tubes were attached, the openings pointing in opposite directions. When water was boiled in the sphere, the steam escaped through the tubes and, as a result of what we now call the law of action and reaction, caused the sphere to rotate rapidly. (The modern lawn sprinkler works in precisely this fashion, using the force of flowing water rather than steam.)
Hero had produced a steam engine. This does not represent the invention of the device, since it did not affect society. It is mentioned only as a curiosity and because it makes one wonder what might have happened if Greek science had continued unabated, uncrushed by the weight of Roman lack of interest.
╩Ultraviolet Sparks
1887 AD
GERMANY
The German physicist Heinrich Rudolph Hertz (1857-1894) was interested in British mathematician James Clerk Maxwell's (1831-1879) equations. As part of his investigation of electromagnetic effects in the light of those equations, he set up an electrical circuit that oscillated. It surged alternately, first into one, then into the other of two metal balls separated by an air gap. Each time the potential reached a peak in one direction or the other, it sent a spark across the gap.
In the course of these experiments, Hertz noted that when ultraviolet light shone on the negative terminal of the gap, the one from which the spark issued, the spark was more easily elicited. This did not seem to have anything to do with what he was trying to observe, so he noted the matter but did not follow it up.
This was the first observation of the effect of light on electrical phenomena, however. This photoelectric effect turned out to be extremely important.
öThe Hip Bone's Connected to the...
1972 AD
GREAT BRITAIN
X rays had been used in medical diagnosis for three-quarters of a century, but in all that time they had been used only to obtain a two-dimensional photograph of a three-dimensional body.
In 1972 a technique was introduced called computerized axial tomographic scanning (CAT scan), in which numerous X-ray "stills" were taken in such a way that they could be put together to form a three- dimensional image.
In another medical advance, the British surgeon John Charnley devised the first satisfactory plastic replacement for the fitting of the thighbone into the hip socket, in 1972, thus preventing crippling through joint degeneration.
6Easier than Dragging
3500 BC
SUMERIA (SOUTHERN IRAQ)
Where objects are too heavy to be carried by hand, transportation over land becomes a problem. Even where land is fairly smooth, there is considerable friction, whether the ground is sandy, pebbly, or grassy. Heavy objects had to be dragged on sledges by sheer force at first, and even when animals stronger than humans were used (oxen, for instance), it was slow going.
It could be made easier if crude rollers in the form of wooden logs were placed under sledges. The rollers turned rather than dragged, and that cut down on friction considerably. It meant less work, but might actually take more time, as rollers had to be picked up from the back and put down again in front. What is needed is an axle and wheels.
We don't know how someone came to think of attaching two rollers to the sledge back and front in such a way that they rolled inside the straps that held them and remained with the sledge at all times. At the end of each roller, solid wooden wheels were then placed to lift the sledge off the ground, and the wheels turned freely.
A wheeled cart moves more quickly and with far less effort than a sledge, even a sledge on rollers, so that such carts marked a revolution in land transportation. They made trade easier, for one thing.
Such carts had showed up in Sumeria by 3500 B.C.
¢Which Way the Wind Blows
1831 AD
CONNECTICUT
An American meteorologist, William C. Redfield (1789-1857), traveled through Connecticut soon after a hurricane had ripped through New England on September 3, 1821. He noticed the manner in which the trees had fallen and deduced that, as the storm had traveled northeastward, the winds had spiraled.
He spent the next ten years studying storms and in 1831 published his evidence to the effect that storm winds whirl counterclockwise around a center that moves in the normal direction of the prevailing winds.
Eventually it was discovered that this was true only in the northern hemisphere. In the southern hemisphere, storm winds whirl clockwise.
UMind and Mesmer's Method
1774 AD
VIENNA, AUSTRIA
Throughout history, diseases had been cured (so it was said) by various mystic rites, by the laying on of hands, the saying of prayers, and so on.
In 1774 the German physician and mystic Franz Anton Mesmer (1734-1815) began to apply science to this by waving magnets over his patients, and effecting cures in some cases. Later, he discovered that magnets were unnecessary and that the same happy results could be achieved by simply passing hands over the patient. He claimed to be making use of animal magnetism.
Naturally, in some cases he did not effect a cure, and he was driven out of Vienna, where he first practiced, as a quack. He went to Paris, where again he was first popular and then forced to leave. His methods were examined by such men as Franklin and Lavoisier.
Franklin, for one, although he condemned Mesmer's mysticism, recognized that the mind influenced the body: that it could cause disorders and that it could be used to correct them.
What Mesmer was dealing with (without understanding it as well as Franklin did) were psychosomatic ailments, where often it is only necessary for patients to believe they will be cured in order to be cured. Mesmer's methods, refined and freed of some of their mumbo jumbo, became respectable half a century later as hypnotism, and some of them entered psychoanalysis later still.
öThe Key to Computing
1960 AD
DALLAS, TEXAS
Since transistors had first been developed in 1948, they had been made steadily smaller, cheaper, and more reliable. By 1975 they had become so small, and the circuits upon them had been etched in so compact a manner, that they could be called microchips.
This meant that computers also could be made very small, very cheap, and very powerful. And this made possible personal computers, the first of which were introduced in 1975, foreshadowing the coming of word-processors and robots.
With the microchip, the computer was no longer suitable only for government and large industries. It began to invade the domain of the general public.
Storehouses of Knowledge
640 BC
NINEVEH
Welcome to the Science Adventure Library! You can use the card catalog in the library picture to find any topic you wish.
Just click on the card catalog drawer containing the topic you want to find, then click on the topic itself. Science Adventure will take you right to a screen on that topic.
As a shortcut, just type the topic you want to find from anywhere in Science Adventure. The index will automatically appear and take you to the index entry you have typed.
Though electronic libraries such as this one are new, books and libraries have been around for ages.
Books, whether clay bricks covered with cuneiform or papyrus covered with hieroglyphics and rolled up (the word volume is from the Latin word for "to roll up") were hard to come by in ancient times. To get an additional copy of a book, it had to be copied over, stroke by stroke, by a meticulous and thoroughly literate scribe. Such copying took a long time and was hard work, so that books were both rare and expensive.
Only a few people could own books, and a library (from a Latin word for "book") consisting of several books must have been the mark of a rich man or the painfully accumulated store of a scholar. Only monarchs with the resources of kingdoms behind them could accumulate large libraries in the modern sense.
The first such monarch that we know of was Ashurbanipal. He arranged to have every book in his kingdom copied and the copy placed in his library at Nineveh. He ended up with thousands of books, all carefully cataloged.
tIndia: Home of Eastern Religion
1990 AD
At the upper edge of the Indian subcontinent you can see the Himalayan Mountains. In this range is Mt. Everest, at 29,028 feet above sea level, the tallest mountain in the world.
Though the mountains are tall, they have not always been tall enough to keep out invaders.
Thousands of years ago, starting with Aryan tribes from Central Asia, invaders have filed through the famous Khyber Pass in the northwest of this mountain range to conquer the land.
Though empires have risen and fallen here, India's major influence upon the world is undoubtedly religious. Here Hinduism was developed and is still powerful today, and from here (though it is no longer very influential in India) Buddhism had its start.
While Hinduism is not a major influence outside India, Buddhism is. Buddhism has become a major religious force throughout Southeast Asia and as far away as Japan.
dStealing the Revolution
1790 AD
PAWTUCKET, RHODE ISLAND
Great Britain's economic position was improving enormously with its ingenious new textile machinery and the manner of powering it by steam. It was easy for the British leaders to see that if they could retain a monopoly on this Industrial Revolution, Britain might easily become the strongest power in the world -- economically, at any rate.
For this reason, what we would today call an "iron curtain" was clamped down. Blueprints of the new machinery were not allowed to leave the country, and neither were engineers who were experts in the new technology.
The new nation of the United States wanted the new technology to aid in its economic independence from Great Britain, without which its political independence wouldn't amount to much. It therefore did its best to steal the knowledge by encouraging defectors. It found its man in Samuel Slater (1768-1835).
Slater was an engineer who knew the new technology intimately, but who also knew that he could advance only so far in the class-ridden society of Great Britain. The United States was offering money for his knowledge and he decided to go for it. He couldn't take any blueprints with him, of course, so he painstakingly went about memorizing every detail of the machinery. He then disguised himself as a farm laborer and sneaked out of the country. In 1789 he arrived in the United States and made contact with rich merchants in Rhode Island.
In 1790, working from memory, Slater began building the first American factory based on the new machinery, in Pawtucket, Rhode Island.
In this way, the Industrial Revolution came to the United States, and once the process of proliferation began there was no stopping it. It continues to this day. Of course, when other nations try to make use of our technology in the same way that we made use of Great Britain's, we are, very naturally, indignant.
Light You Can't See
1800 AD
BATH, ENGLAND
It seemed natural to suppose that light, by its very nature, could be seen; light that could not be seen would be a contradiction in terms. Yet invisible light existed.
British astronomer William Herschel (1738-1822) in 1800 had formed a sunlight spectrum and tested different parts of it with a thermometer to see if some colors delivered more heat than others. He found that the temperature rose as he moved toward the red end of the spectrum, and it seemed sensible to move the thermometer just past the red end in order to watch the heating effect disappear.
Except that it didn't. The temperature rose higher than ever at a spot beyond the red end of the spectrum. The region was called infrared (below the red).
How to interpret the region was not readily apparent. The first impression was that the Sun delivered heat rays as well as light rays and that heat rays refracted to a lesser extent than light rays. A half-century passed before it was established that infrared radiation had all the properties of light waves except that it didn't affect the retina of the eye in such a way as to produce a sensation of light.
Herschel's discovery of infrared radiation naturally created a stir. German physicist Johann Wilhelm Ritter (1776-1810) was also studying the Sun's spectrum, but he was more interested in the chemical changes it brought about.
It had been known for nearly two centuries that light broke down the white compound silver nitrate, darkening it (by liberating tiny specks of metallic silver). This was first reported in 1614 by an Italian chemist, Angelo Sala (1576-1637).
Ritter soaked strips of paper in silver nitrate solution and placed them in different sections of the spectrum to see how rapidly they darkened. He found that the darkening was least rapid in the red end of the spectrum and took place faster and faster as one progressed toward the violet end. Ritter, perhaps influenced by Herschel's experience, proceeded to place strips of soaked paper beyond the violet end, where nothing could be seen. There the darkening proceeded faster still. Apparently, there was radiation beyond the violet end of the spectrum as well as beyond the red. The new radiation was called ultraviolet (the prefix ultra is from a Latin word meaning "beyond").
{Connecting Ear and Throat
1552 AD
ITALY
Flemish anatomist Andreas Vesalius's (1514-1564) new anatomy spurred on the field generally.
The Italian anatomist Bartolommeo Eustachio (1520-1574) prepared a book on anatomy in 1552, nine years after Vesalius's. In some respects it was more accurate than the earlier book, but the illustrations were not as beautiful.
Eustachio described a narrow tube connecting the ear and the throat, which has been known as the Eustachian tube ever since, though it may have been discovered by a Greek physician, Alcmaeon (6th century B.C.), two thousand years before.
Eustachio was also the first to describe the adrenal glands.
Jupiter's Varied Moons
1979 AD
The probes Voyager 1 and Voyager 2 passed by Jupiter in March and July, respectively, of 1979. The most interesting result was that they gave humanity its first close look at the four Galilean satellites.
The satellites are subject to tidal heating from Jupiter, a heating that increases rapidly as distance from Jupiter decreases. Thus, Ganymede and Callisto, the outermost pair, are both covered with craters as might be expected and seem to be made up largely of icy material.
Europa, second-closest to Jupiter, is not cratered -- it has, in fact, the smoothest solid surface yet seen in the Solar System -- but cracked and criss-crossed with lines (rather like the old maps of Mars that showed the supposed canals). Apparently Europa is covered with a worldwide glacier that has liquid underneath. Any cosmic collision that might ordinarily cause a crater merely cracks the glacier, and the hole produced is then repaired by the formation of additional ice.
Io, the closest of the four satellites to Jupiter, has no water at all, the heating having driven it off. In fact, the inner heating produces active volcanoes, which the probes photographed in actual eruption. Sulfur dioxide exudes and breaks up into sulfur and oxygen. Io's surface is therefore covered by a yellow to red layer of sulfur, which fills in any but the most recent of craters. The eruptions also account for the thin gas that fills Io's orbit, forming a doughnut around Jupiter.
In addition to all of this, three more small satellites were discovered, all of them closer to Jupiter than any that had been discovered from Earth. This made sixteen satellites all told for Jupiter. Finally, very close to Jupiter, a thin ring of debris was found, so that Jupiter joined Saturn and Uranus in being a ringed planet.
¬Japan: The Rising Sun
1990 AD
Almost 150 years ago, Japan, the land of the rising sun, was isolated. Earlier the country had cut off contact with the outside world. But then American Commodore Matthew Perry, in search of new markets for American goods, forced the Japanese to open their ports. And considering it was forced to do so, Japan acted with surprising speed and enthusiasm.
From a society little removed from feudalism, Japan quickly rose to become a mighty military power that defeated the Russians, Chinese and Koreans. And during World War II the country engaged the United States in some of the most difficult battles it ever faced.
World War II was ended when American bombers dropped atomic bombs on Hiroshima and Nagasaki, near the south tip of the large island of Honshu.
Since its World War II defeat, Japan has risen again, but this time as a powerful economic nation.
The peninsula to the left of Japan is Korea, which has been divided into two halves following World War II. The north half was occupied by the Soviet Army and adopted communism, while the southern half was occupied by the United States and became capitalist and mostly democratic, though with instances of military rule.
4Cowpox Now, Smallpox Never
1796 AD
GLOUCESTERSHIRE, ENGLAND
Inoculation had been used to fight smallpox for some eighty years, but it was dangerous.
The English physician Edward Jenner (1749-1823) knew that in his native Gloucestershire there were tales to the effect that anyone who caught cowpox (a very mild disease, prevalent among cows, that somewhat resembled smallpox) was thereafter immune not only to cowpox but also to smallpox. (Since milkmaids almost invariably caught cowpox early and then never got smallpox, they retained a clear complexion. This in itself may have been enough to fuel the romantic cliché of the time concerning pretty milkmaids.)
Finally Jenner decided to test the matter. On May 14, 1796, he found a milkmaid who was undergoing an attack of cowpox. He took the fluid from a blister on her hand and injected it into an eight-year-old boy named James Phipps who, of course, got cowpox. Two months later, Jenner inoculated the boy with smallpox in the manner usual for those days. The boy did not get smallpox. Two years later, he found someone else with active cowpox and tried again. It worked this time also, and he felt it safe to announce his discovery. The Latin word for cow is vacca, so cowpox is vaccinia.
Jenner coined the word vaccination to describe his use of cowpox inoculation to create immunity to smallpox. In this way, he founded the science of immunology.
Such was the dread of smallpox that the new technique was instantly adopted and quickly spread all over Europe. It was the first case of a serious and frightening disease that could be reliably prevented.
kPowered by Exhaust
1941 AD
RUGBY, UNITED KINGDOM
During the forty-year history of air flight, planes had been propelled through the air by the aptly named propeller. There was no question, though, that a plane could also be made to move through the air, perhaps even more quickly and efficiently, by means of the rocket principle -- by burning fuel and ejecting a jet of exhaust gas at high speed (such planes are therefore called jet planes).
The advantage jet planes had over rockets such as those developed in 1926 by American physicist Robert Hutchings Goddard (1882-1945) was that they traveled through the atmosphere, so they needed to carry only fuel and could make use of the oxygen in the surrounding air as the oxidizer.
Plans for engines that made some use of the jet principle can be traced back to 1921, but the first patent for a jet engine of the type used today was obtained by a British aeronautical engineer, Frank Whittle (b. 1907), in 1930. The first jet plane making use of Whittle's engine was flown in May 1941. Jet planes were developed too late to play much of a role in World War II, but they came into their own afterward.
√Galileo Spots Jupiter's Moons
1610 AD
ITALY
Other than the Sun and the Moon, the planets known to the ancients were seen merely as points of light. When Galileo Galilei (1564-1642) turned his telescope on them, however, he found that they expanded into little orbs. Clearly, they were extended bodies but were too small, or too distant, or both, to show as orbs to the unaided eye. (The stars, however, remained points of light even when viewed by telescope.)
Jupiter was not only an orb but, in January 1610, Galileo observed four dimmer objects in its immediate vicinity. As he watched from night to night, he saw that they were circling Jupiter, as the Moon circles the Earth. They were, in short, four moons of Jupiter. German astronomer Johannes Kepler (1571-1630) later referred to them as satellites, a Latin word referring to those who remain close to someone rich or powerful in the hope of picking up scraps and favors.
Jupiter's four satellites were the first objects ever seen in the sky that clearly circled some object other than Earth, which was a strong point against Ptolemy's geocentrism. For that reason, the discovery displeased the rigidly religious. Some refused to look through the telescope in order to avoid seeing the satellites. One pointed out that since the satellites were not mentioned by Aristotle, they clearly did not exist.
Seeking support from Cosimo II (1590-1621) of the Medici family, who in 1609 had become grand duke of Tuscany (an Italian state with its capital at Florence), Galileo called the satellites "the Medicean stars." Fortunately, the name didn't stick. The German astronomer Simon Mayr, known by his Latin name of Simon Marius (1570-1624), saw the satellites soon after Galileo. He named them, in order of increasing distance from Jupiter, Io, Europa, Ganymede, and Callisto, after individuals closely associated with Jupiter (Zeus) in the Greek myths.
Galileo also noted that Jupiter and Saturn both had orbs that did not appear perfectly circular, as did the orbs of the Sun and Moon, but were somewhat elliptical.
<A Pioneer by Jupiter!
1973 AD
CAPE CANAVERAL, FLORIDA
On March 2, 1972, a Jupiter probe, Pioneer 10, had been launched -- the first probe intended to yield information concerning the outer Solar System. After passing safely through the asteroid belt, Pioneer 10 reached the vicinity of Jupiter on December 3, 1973, and passed only 85,000 miles above Jupiter's surface, going right through the planet's magnetosphere. Jupiter's magnetic field, forty times as energetic as Earth's, made itself felt at a distance of 4,300,000 miles from the planet.
From the data obtained by the probe, it was possible to build a picture of the planet's structure. It would seem that Jupiter is a ball of hot liquid hydrogen mixed with some helium (a constitution much like that of the Sun).
The temperature rises rapidly with distance beneath the visible cloud surface. At 600 miles below, it is already 3,600° C; at 1,800 miles below, it is 10,000° C; at 15,000 miles below, it is 20,000° C; and at the very center of Jupiter, it is 54,000° C. Below 15,000 miles, hydrogen takes on a metallic form.
Pioneer 10 carried a message from Earth etched into a 6- by 9-inch gold-plated aluminum slab. It showed a man and woman next to an outline of Pioneer 10 drawn to scale. Also included were details of the Solar System and its location in the Universe relative to distant pulsars.
zIsland Universes
1755 AD
KONIGSBERG, PRUSSIA (KALININGRAD)
Do the stars in the sky spread out evenly and indefinitely in all directions or are they contained in a finite volume with a particular shape? To the eye it might seem that the first alternative is correct -- except for the Milky Way. Once Galileo showed that the Milky Way consisted of very many, very dim stars, it became clear that there are far more stars in the direction of the Milky Way than in other directions. In 1750, an English astronomer, Thomas Wright (1711-1786), maintained that the stars formed a flattened finite system, but his writings were so mystical that it was hard to take him seriously.
In 1755, however, the German philosopher Immanuel Kant (1724-1804) made a similar suggestion. He said the Sun was one of a large number of stars that existed in a lens-shaped conglomerate, and that the Milky Way was the result of looking into the sky along the long axis of the lens. This conglomerate came to be called the Galaxy, from a Greek word for the Milky Way. Kant also suggested that certain nebulas, such as the one in Andromeda, were other galaxies or, as he called them in a dramatic phrase, "island universes."
In this, Kant was quite correct, but it was to be over half a century before the Galaxy's existence could be clearly demonstrated and over a century and a half before the existence of other galaxies could be demonstrated.
≡Tut's Tomb
1352 BC
EGYPT
The ancient Egyptian pharaohs had magnificent burials, and much in the way of gold and other precious materials was interred with them. Every effort was made to keep the tombs from being rifled and the contents stolen, even to the extent of placing the tomb at the center of a solid pyramid.
All efforts failed. All tombs were burglarized -- and a good thing, too. If all the gold had remained buried, it would have ruined the economy of the ancient world. The tomb-robbers did civilization a remarkable favor by restoring the tomb contents to circulation.
By 1000 B.C., the great days of the pharaohs were over, and every last tomb was empty -- except one. From 1361 to 1352 B.C., the pharaoh ruling over Egypt had been Tutankhamen. He was only about 21 when he died, but he was given the usual sumptuous burial. His grave was at once robbed, but for a wonder, the robbers were caught in the act and forced to return the loot.
Perhaps the fact that the grave had been looted had gotten out but the return had been kept quiet. At any rate, no further effort at looting was made for two centuries. Then, while a grave was being excavated for a later pharaoh, the resulting showers of stone chips covered the entrance to Tutankhamen's tomb, hiding it so effectively that it came down to the twentieth century intact.
A British archaeological expedition under George Edward Stanhope Molyneux Herbert, Earl of Carnarvon (1866-1923), and Howard Carter (1873-1939) found the first sign of the entrance to Tutankhamen's tomb on November 4, 1922. Three days later they reached the sealed burial chamber, and a rich treasure trove of ancient Egyptian artifacts was uncovered. It gave tremendous impetus to Egyptian studies.
It also gave rise to the silly tale of the "Pharaoh's curse," when Lord Carnarvon died five months later of an infected mosquito bite complicated by pneumonia, but surely no sane man could believe Tutankhamen had anything to do with it. Carter lived on for seventeen years after opening the tomb.
Laser: Hotter than the Sun
1960 AD
LOS ANGELES, CALIFORNIA
The principle of the maser, which produced an intense, coherent, monochromatic beam of microwaves, could be applied to any wavelength, including those of visible light. This had been pointed out by American physicist Charles Hard Townes in 1953.
The first maserlike device capable of producing an intense, coherent, monochromatic beam of visible light was constructed in May 1960 by the American physicist Theodore Harold Maiman (b. 1927), making use of the three-level principle worked out in 1956 by Dutch-born American physicist Nicolaas Bloembergen (b. 1920).
Maiman designed a ruby cylinder with its ends carefully polished flat and parallel and covered with a thin silver film. Energy was fed into it from a flash lamp until it emitted a beam of red light.
The coherent light so produced had only a slight tendency to spread and could be concentrated into so tiny a point that, at that point, temperatures could be reached far higher than the surface of the Sun. The device was first called an optical maser, but since it could be described as light amplification by stimulated emission of radiation, the initials of that phrase were used and it came to be called a laser.
Lasers soon proliferated into many different types, with many different uses.
çNo Grooves to Wear Out
1972 AD
NETHERLANDS
Since the phonograph had been invented, sound had been reproduced through the vibration of a needle running along a groove. Eventually, of course, both needle and groove wore out, so that sound reproduction became imperfect.
In 1972 laser disks (also called compact disks) became practical. Here the sound was picked up by a laser beam, which translated it into information recorded on flat disks in the form of microscopically small pits. These could then be picked up by other laser beams. There was no question of wear, more sound could be packed onto a given surface, and reproduction was nearer perfection than ever before.
åHow Earth's Core Stays Hot
1906 AD
DISTRICT OF COLUMBIA, UNITED STATES
In 1906 the American geologist Clarence Edward Dutton (1841-1912) suggested that pockets of radioactivity in the Earth's crust delivered enough heat over time to activate volcanic action.
This was the beginning of the understanding that radioactivity added substantial heat to the Earth's crust, enough to balance that lost by radiation, so that any attempt to judge the Earth's age by calculating the time it took Earth to "cool down" from an initial high temperature was far off base. Earth could be billions of years old and still retain a heated interior.
Dutton also developed methods for determining the depth of earthquake origins and the velocity with which earthquake waves traveled through the Earth. This opened the way for a technique that finally offered strong evidence concerning the physical and chemical nature of the Earth's deep interior.
4Observe, But Measure Too
1769 AD
FRANCE
Although Scottish chemist Joseph Black (1728-1799) had demonstrated the usefulness of quantitative measurements in chemistry, what made them an integral part of the science was the work of French chemist Antoine-Laurent Lavoisier (1743-1794), who is universally considered the father of modern chemistry.
There were at this time some who still clung to the Greek theory of elements and their changeability. They argued that if water were boiled for a long time, a sediment appeared, and that this was clearly a conversion of water into a kind of earth, in line with Greek thinking.
Lavoisier decided, in 1769, to test this matter. He boiled water for 101 days in a device that condensed the water vapor and returned it to the flask, so that no water was lost in the process. He weighed both water and vessel before and after the boiling.
Sediment did appear, but the water did not change its weight during the boiling, so the sediment wasn't formed out of the water. The flask itself, however, had lost an amount of weight just equal to the weight of the sediment.
In other words, the sediment was material from the glass, slowly etched away by the hot water and precipitating in solid fragments. Here was a clear-cut example of the way in which observation, without measurement, could be useless and misleading.
A Theory of the Obvious
260 BC
SYRACUSE, ITALY
Levers were used in prehistoric times. It is no great trick for a lively mind to try to pry up a rock with a long stick and to find that it works better if another, smaller rock is placed under the stick to give the stick something to push against. It would then quickly be discovered that the closer the small rock is to the big rock being pried up, the easier the prying gets.
Nevertheless, the precise mathematics of lever action was not worked out until the Greek scientist Archimedes (ca. 287-212 B.C.) did it about 260 B.C.
You might say, "What difference does it make that scholars worked out fancy theories and mathematics for levers, when practical people had been actually using such devices for thousands of years?"
The point is that use without theory is largely hit and miss. Advances are made, yes, but slowly. Once a useful theory is worked out, however, it is like removing a blindfold. It becomes obvious how a device might be improved, or what new observations need to be made. With a theory, advances speed up enormously. Therefore we give Archimedes credit for the principle of the lever, regardless of how long the lever had been in use before his time.
Archimedes also worked out the principle of buoyancy, the manner in which any object immersed in a fluid displaces a volume of fluid equal to its own volume. This provided a way of measuring volume, a way of explaining why some things float and some don't, and so on. Archimedes grasped the principle quite suddenly when he lowered himself into a public bath and noticed the water overflow.
The story is that he sprang out of the bath and raced home nude, shouting "Eureka! Eureka!" ("I have it! I have it!"). He had been given the problem of checking whether a golden crown was adulterated with a less dense metal or not, without damaging the crown. For that he had to know the volume, and the buoyancy effect would give it to him. (The ancient Greeks, by the way, did not mind nudity, so Archimedes' action was not as bizarre as might be thought.)
7Lewis and Clark Expedition
1804 AD
MISSOURI RIVER, USA
President Jefferson wanted the new territory of Louisiana to be explored. For the purpose, he chose Meriwether Lewis (1774-1809), who in turn chose William Clark (1770-1838). These two, with a party of about forty young men, made up the Lewis and Clark Expedition.
They went to St. Louis where they remained over the winter of 1803-1804. Then on May 14, 1804, they moved up the Missouri River and followed it back to its source. This brought them to the American border, but they went on anyway into the Oregon Territory, the only part of the American continents that had still not been effectively claimed by any one power. They followed the Columbia River to the Pacific Ocean, which they reached on November 15, 1805, and then returned to St. Louis, which they reached on September 23, 1806. This was the first trip across the United States from ocean to ocean and back. The Lewis and Clark Expedition brought back information on the Indian tribes of the region, on animal life (including huge herds of bison), on plant life, and on natural features.
jA Jarring Experience in Leyden
1745 AD
LEYDEN, NETHERLANDS
The glass sphere English physicist Francis Hauksbee (ca. 1666-1713) produced in 1706 was surpassed as an electricity-storing device by the work of a Dutch physicist, Pieter van Musschenbroek (1692-1761).
In 1745 he placed water in a metal container suspended by insulating silk cords, and led a brass wire through a cork into the water. He built up an electric charge in the water but did not realize how much had accumulated in the device until an assistant happened to pick it up and touch the brass wire outside the cork. The container promptly discharged all of the electric charge it had accumulated and gave the poor assistant a fearful shock. It was the first good-sized artificial electric shock anyone had ever received. (The lightning stroke is worse, of course, but it is a natural electric shock.)
A German physicist, Ewald Georg von Kleist (1700-1748), independently produced the same device at about the same time. He discovered the strength of the charge by accidentally discharging it into his own body. He said he wouldn't take another such shock to be the king of France and worked with the device no longer.
Because Musschenbroek popularized the device and because he worked at the University of Leyden in the Netherlands, the electricity-storing device came to be called a Leyden jar. It was at once made use of by other experimenters.
Lightning Fire
500,000 BC
BEIJING, CHINA
The cave near Beijing had traces of campfires. This meant that fire had been "discovered" some five hundred thousand years ago. Here is a characteristic that marks off human beings from all other organisms. Every human society in existence, however primitive, has understood and made use of fire. No living creature other than human beings uses fire in even the most primitive fashion.
I have put discovered in quotation marks, for fire was not discovered in the usual sense. Lightning could start a fire ever since Earth's atmosphere gained enough oxygen to sustain one and Earth's land surface possessed a forest cover that could burn, and that means for some four hundred million years. From that fire, then as now, any animal capable of fleeing would flee.
2Lilienthal: Grace in Flight
1891 AD
GERMANY
Four decades had passed since English engineer George Cayley (1773-1857) had built the first glider capable of carrying a human being. Now a German aeronautical engineer, Otto Lilienthal (1848-1896), made them into things of grace and ability. As early as 1877 he had shown that curved wings were superior to flat wings as far as gliding was concerned. In 1891 he launched himself on his first glide. He died a few years later in a crash landing, but he made gliding popular, and it turned out to be not too long a step from a glider to an airplane.
kNew York-Paris Nonstop
1927 AD
PARIS, FRANCE
On May 20-21, 1927, the American aeronaut Charles Augustus Lindbergh (1902-1974) flew from New York to Paris. Others had flown across the Atlantic Ocean before, but Lindbergh did it nonstop and alone in a small single- engine plane, Spirit of St. Louis, in a flight that kept him awake for 33-1/2 hours. With this feat, aeronautics came of age.
─Lister Washes His Hands
1865 AD
GREAT BRITAIN
Anesthetics had come into use nearly twenty years before, but if the process had become more nearly painless, it still remained deadly. The operation might be successful, yet the patient might develop inflammation and die. In 1865 the British surgeon Joseph Lister (1827-1912) learned of French chemist Louis Pasteur's (1822-1895) germ theory of disease and it occurred to him that death after operations might result from a germ infection to which the traumatized tissues were particularly susceptible. The germs producing the infection might come from the doctors themselves, or from their instruments.
Lister therefore instituted the practice of using phenol solutions to clean hands and instruments, and the death rate after operations dropped at once. Hungarian physician Ignaz Phillipp Semmelweiss (1818-1865) had attempted the same thing seventeen years earlier, but without the justification of Pasteur's theory, and physicians refused to listen.
This shows the importance of theory in the most practical of affairs.
Eventually, chemicals less irritating and more effective than phenol were used, and antiseptic (from Greek words meaning "against putrefaction") surgery became the rule.
ΦOne Giant Leap for Mankind
1969 AD
THE MOON
At 4:18 P.M. eastern daylight savings time on July 20, 1969, Neil Alden Armstrong (b. 1930) and Edwin Eugene Aldrin, Jr. (b. 1930) brought the lunar module of Apollo 11 to the surface of the Moon, while Michael Collins (b. 1930) remained in orbit about the Moon. Neil Armstrong stepped out, the first human being to set foot on any world other than the Earth, saying "That's one small step for a man, one giant leap for mankind." John Kennedy's goal of reaching the Moon by the end of the decade had been reached.
Earth safely at 12:51 P.M. eastern daylight savings time on July 24, eight days after takeoff. A second American ship landed on the Moon in November 1969, and astronauts remained on the Moon's surface for 15 hours.
uFirst Time Around the Earth
1523 AD
STRAIT OF MAGELLAN
Ferdinand Magellan (ca. 1480-1521) is the English name of a Portuguese navigator, financed by Spain, who sailed west with five ships on September 20, 1519, in search of the Far East. When he reached the eastern bulge of South America, he began looking for a southern end to that continent, which he found on October 21. For over five weeks, he felt his way through what is now known as the Strait of Magellan, amid storms, and on November 28, it opened into an ocean and the storms ceased. As Magellan sailed on and on through good weather, he called this new ocean the Pacific.
However, the Pacific Ocean was far larger than anyone would have expected, and was sadly free of land. For ninety-nine days, the ships sailed through unbroken sea, and the men underwent tortures of hunger and thirst. Finally they reached the island of Guam, then they sailed westward to the Philippine Islands.
There, on April 17, 1521, Magellan died in a skirmish with the inhabitants. The expedition continued westward, however, and a single ship with eighteen men aboard, under the leadership of Juan Sebastián de Elcano (ca. 1476-1526), finally arrived back in Spain on September 7, 1522. This first circumnavigation of the globe had taken three years, and if the loss of life can be set aside, the single returning ship carried enough spices to make the voyage a complete financial success.
The voyage showed beyond doubt, at last, that the Earth was 25,000 miles in circumference, as Eratosthenes had calculated in about 240 B.C. It showed also that the Earth possessed a worldwide ocean in which the continents existed like huge islands.
Magnets of Magnesia
500 BC
MAGNESIA (MANISA), ASIA MINOR
In the sixth century B.C. it was discovered (by a shepherd, according to legend) that a certain kind of ore attracted iron. Since the ore was found near the Asia Minor city of Magnesia, it came to be called the Magnesian stone, or in English, a magnet, and the phenomenon was magnetism. The phenomenon was first studied by Thales. It was eventually found that stroking with the magnetic ore could turn a sliver of iron or steel into a magnet.
Somehow it was discovered that if a magnetic sliver was allowed to turn freely, it would come to rest pointing in a north-south direction. We don't know how this fact was discovered, but the Chinese were the first to be aware of it.
It is referred to in Chinese books dating as far back as the second century.
The Chinese never used the magnet for direction-finding in navigation, because by and large they were not great navigators. The Arabs may have learned of it from them, however, and perhaps some Crusaders learned of it from the Arabs.
United States Enters Space Age
1958 AD
CAPE CANAVERAL, FLORIDA
In 1958 the United States entered the Space Age. The Soviet Union had placed two satellites in orbit in 1957, Sputnik I on October 4 and Sputnik II on November 3. The latter carried a dog, the first living animal to be placed into orbit.
The first successful American satellite was Explorer I, which was launched on January 31, 1958. It carried counters designed to estimate the number of charged particles in the upper atmosphere, and detected about the expected concentrations of particles at heights of up to several hundred miles, but at higher altitudes the number fell to zero. Two other satellites launched soon afterward, one by the United States and one by the Soviet Union, recorded the same phenomenon.
The American physicist James Alfred Van Allen (b. 1914) did not believe the count could really fall to zero. He felt that what happened was that the count went so high it put the counter out of action.
When Explorer IV was launched by the United States on July 26, 1958, it carried special counters that were shielded with a thin layer of lead to keep out most of the radiation (rather like wearing sunglasses to protect the eyes). The radiation that penetrated the lead was not enough to overwhelm the counters, and now the count went up and up and up with increasing altitude -- far higher than scientists had expected.
It appeared that surrounding the Earth, outside the atmosphere, there were belts containing high concentrations of charged particles that moved along the lines of force of Earth's magnetic field. These particles approached the Earth's surface in the neighborhood of the Earth's magnetic field. There they were responsible for the aurorae and, at times of unusually high concentration, for magnetic storms that affected the compass and electronic equipment. These belts were at first called the Van Allen belts but were eventually referred to as the magnetosphere.
This was the first important discovery -- an entirely unexpected one -- to be made as a result of the launching of artificial satellites.
How Far to Mars?
1672 AD
CAYENNE, FRENCH GUIANA
Nineteen centuries before, Hipparchus (fl. 146-127 B.C.) had determined the distance to the Moon. Since then, no further heavenly distance had been determined accurately. The parallaxes of all other heavenly bodies were far too small to measure with the unaided eye, and the telescopes weren't quite good enough to do the job.
However, German astronomer Johannes Kepler's (1571-1630) elliptical orbits and his three laws of planetary motion had made it possible to build a model of the Solar System in the proper proportions. If any planetary distance could be obtained, then all the other distances would be known too.
Italian-born French astronomer Gian Domenico Cassini (1625-1712) tackled the job. Thinking his telescope might be good enough if he viewed Mars from two places sufficiently far apart, he sent another French astronomer, Jean Richer (1630-1696), to Cayenne in French Guiana on the northern shore of South America.
In 1672 Cassini determined the position of Mars against the stars as seen from Paris and, using the position of Mars as given in reports from Cayenne, worked out the parallax of Mars. That gave him the distance between Mars and Earth at that time, and from that he could calculate the other distances of the Solar System.
From his figures, he determined that the Sun was 87,000,000 miles from the Earth, as compared with the 5,000,000-mile distance that Aristarchus had estimated. Cassini's estimate was 7 percent too low, but for a first try it was amazingly close.
For the first time, an appropriate idea of the size of the Solar System was obtained. Even allowing for the slightly low figure Cassini had, it was clear that the orbit of Saturn, which was then the farthest known planet, had to be over 1,600,000,000 miles across.
The stars must be farther still. No one yet knew how much farther the stars must be, but Cassini gave human beings the first shocking realization of how small they and their world were compared to the Universe. There were other and greater shocks yet to come.
ëWhere are the Martians?
1976 AD
MARS
In 1975 two Mars probes had been launched by the United States, Viking 1 on August 20 and Viking 2 on September 9. Both went into orbit about Mars in mid-1976, and they took the best photographs of the Martian surface yet.
On July 20, 1976, Viking 1 came down to the Martian surface at what would have been, on Earth, the edge of the tropical zone. Some weeks later Viking 2 came down in a more northerly position. In coming down, they discovered that the Martian atmosphere, though chiefly carbon dioxide, was also 2.7 percent nitrogen and 1.6 percent argon.
The Martian surface was rocky, as Earth's surface is. The Martian surface, however, was richer in iron and sulfur and poorer in aluminum, sodium, and potassium. There was no sign of life on Mars on a scale visible to the eye. The Viking probes were equipped to run experiments on Martian soil to see if any microscopic forms of life were present. The experiments were carried through with ambiguous results, but there was no trace of organic material in the soil, and this led astronomers to believe that certain lifelike responses to the experiments were the result of some odd chemical behavior of the soil.
There were signs of dry riverbeds, however, complete with tributaries. It may be that in ages past there was a reasonable supply of liquid water on Mars. If so, where did it go, and what led to such an extreme cooling of the planet?
ÅMaxwell's Lines of Force
1855 AD
UNITED KINGDOM
English physicist Michael Faraday (1791-1867) had introduced the concept of lines of force, but since he knew no mathematics, he could only describe them pictorially.
The British mathematician James Clerk Maxwell (1831-1879) was able to translate Faraday's concept into mathematical form in 1855 and show that the former's intuitive grasp of the subject was completely correct.
"The Home of the West
1990 AD
Here, along the northern regions of the Mediterranean Sea, is the home of much of Western philosophy, government and literature.
In the upper right of the picture, that jagged peninsula and those islands you see in this satellite's-eye view is Greece and the Aegean islands, where Socrates and Plato and Aristotle taught philosophies that affect the world today. And there Homer wrote his Iliad and Odyssey, two foundational works of western literature.
Now sail west across the Adriatic Sea to the boot of Italy. A city called Rome, located near the middle of this peninsula, rose to rule a long-lived empire from the British Isles to the Euphrates River, spreading Greek and Roman culture throughout Europe and serving as a model for republicanism, a form of government still influential today. Rome once controlled the Mediterranean so completely that the Romans called it "Mare Nostrum," or "Our Sea."
The Mediterranean was probably first settled because of its pleasant climate and natural harbors. It has been the chief trade route in history and long before ships ventured out into the stormy Atlantic Ocean, the waters of this inland sea were being crisscrossed by trading vessels.
The name Mediterranean is Latin and means "in the middle of land," and it certainly is, though it is not quite enclosed. At its west end it is almost shut off from the Atlantic Ocean by the Strait of Gibraltar, and on the east it narrows at the Dardanelles, which lead into the Black Sea.
It has one other major connection: the Suez Canal. The canal, built in 1869 by the French, cuts across a narrow strip of Egypt to meet the Red Sea, which connects with the Indian Ocean. Though too small for many of today's large ships, the Suez was once a vital shortcut to the East, and is still a shorter route for smaller ships.
╛Multiplication by Division
1883 AD
BELGIUM
The discovery of the mechanism of cell division by German anatomist Walther Flemming (1843-1905) stimulated many biologists into investigating the matter further.
The Belgian cytologist Edouard Joseph Louis-Marie van Beneden (1846-1910) found that the number of chromosomes in the cells of a particular species was always constant, though the number varied from species to species. (It is now known that there are forty-six chromosomes in human cells.)
Furthermore, he discovered that in the formation of the sex cells (that is, the ova and spermatozoa), the division of chromosomes during one of the cell divisions was not preceded by a doubling. Each egg and sperm cell, therefore, ended with only half the usual number of chromosomes. (This halving of number was called meiosis, from a Greek word meaning "to make smaller"). Consequently, when a sperm cell entered an egg cell in the process of fertilization, the chromosomes reached their normal number for the species, half of them coming from the mother and half from the father.
Meiosis fit in perfectly with Austrian botanist and monk, Gregor Johann Mendel's (1822-188) genetic discoveries but those discoveries were still being ignored.
OMariner Maps Mercury
1974 AD
MERCURY
Mariner 10 had been launched on November 3, 1973. On February 5, 1974, it passed by Venus just 3,600 miles above its cloud layer and then headed for Mercury. On March 19, 1974, it passed within 435 miles of Mercury's surface. It moved into an orbit about the Sun in such a way that it passed near Mercury a second and third time. On the third approach, it passed within 200 miles of Mercury's surface.
Mariner 10 confirmed Mercury's rotation rate and temperature and showed that it had no satellite and no significant atmosphere. It determined the diameter, mass, and density of Mercury with greater precision than had been possible before. In addition, it allowed about three-eighths of Mercury's surface to be mapped.
The photographs it took of Mercury showed a landscape that looked very much like that of the Moon. There were craters everywhere, the largest being 125 miles in diameter. Mercury is not as rich in "seas" as the Moon is. The largest one sighted is about 870 miles across and is called Caloris (heat). Mercury also has cliffs that are a couple of hundred miles long and about 1-1/2 miles high. In addition Mariner 10 discovered that Mercury had a small magnetic field, about a hundredth as intense as the Earth's. This is puzzling, for Mercury does not rotate quickly enough to have a field, if current theories are correct.
éDon't Sneer at Meteors
1794 AD
WITTENBERG, GERMANY
It was the common experience of human beings that objects sometimes fell from the sky. Such falls had been reported. The Kaaba, the sacred black stone of the Muslims, was probably a meteorite that fell from the sky. In Ephesus, a stone was worshipped in the temple of Artemis that was probably a meteorite, and periodically reports of witnessed falls were received.
During the Age of Reason, such tales were discounted and dismissed by men of science.
In 1794, however, a German physicist, Ernst Florens Friedrich Chladni (1756-1827), published a book in which he suggested that meteorites did fall and that this happened because the space near Earth contained the debris of a planet that had once existed but had exploded. This was the first time that a reasonable explanation had been offered for meteorites, and the tide slowly began to turn. It took a while, though.
I The Revolutionary Failure
1881 AD
CLEVELAND, OHIO
In 1881 a German-born American physicist, Albert Abraham Michelson (1852-1931), devised an interferometer, with the financial help of Bell (1847-1922), who had invented the telephone five years before.
This device acted to split a beam of light in two, send the parts along different paths, then bring them back together -- a way of treating light that British mathematician James Clerk Maxwell (1831-1879) had suggested six years before. Then, no one had had an instrument capable of the job; now Michelson had one.
If the two portions of the light traveled precisely the same distance at the same speed, they would then come back together in phase, and the light would be unchanged. If their distance or speed were slightly different, however, the two beams would be slightly out of phase when they rejoined, and interference fringes should be set up such as those English physicist Thomas Young (1773-1829) had detected and used to prove the wave nature of light.
At this time, it was thought that light, being a wave, had to be a wave of something. Consequently, it was supposed that all space was filled with a luminiferous ether. (The word luminiferous is from Latin, meaning "light-carrying," and ether harks back to Aristotle's aether -- see 350 B.C., Five Elements.) This luminiferous ether was thought to be in a state of absolute rest, and the Earth was thought to be moving at some particular speed relative to it, called Earth's absolute motion.
Michelson used his interferometer to measure Earth's absolute motion by sending two halves of a light beam traveling at right angles to each other. Light sent in the direction of Earth's motion through the ether and back again ought to complete its trip a little sooner than light traveling at right angles to the motion and back. Therefore the two halves of the light should rejoin out of phase, and by measuring the width of the interference fringes, one should be able to measure the speed of Earth relative to ether. Once that was known, the absolute motion of all other bodies should follow.
However, the experiment failed. No interference fringes were found. Michelson assumed there was something wrong with the experiment and set about refining it. It took years before he was satisfied that there truly were no interference fringes. That observation helped revolutionize science.
¥Spectacles to Microscopes
1590 AD
AMSTERDAM, NETHERLANDS
It must have dawned on people rather early that there were ways of making small objects appear larger in size. Dewdrops on a leaf or on a blade of grass will make the surface they rest on look larger. Spheres of glass will do the same.
The people who would most notice this sort of thing and be most concerned with it were the spectacle-makers, since the convex lenses used to correct far-sightedness acted to magnify objects.
The spectacle-making industry was most advanced in the Netherlands at this time. It occurred to a Dutch spectacle-maker, Zacharias Janssen (1580-ca. 1638), that if one lens magnified somewhat, two would magnify to a greater extent. He placed a convex lens at each end of a tube and found that magnification was indeed improved. The improvement wasn't great, but Janssen's tube can be viewed as the first microscope, and its descendants were to revolutionize biology.
Home of Three Faiths
1990 AD
THE MIDDLE EAST
What Greece and Rome have been to Western government and philosophy, the Middle East has been to its religious life.
All three of the major western religions (Judaism, Christianity and Islam) have their origin in this area.
At the eastern edge of the Mediterranean Sea, on the right of the picture, is Israel, the home of the Jewish and Christian faiths. Further to the east, across the desert of Saudi Arabia, is Mecca, the most holy city of Islam, and the site where Muhammad first began teaching.
\The Electron's Charge
1911 AD
UNITED STATES
The ratio of the electric charge of the electron to its mass had been worked out and compared with that of ordinary ions by British physicist Joseph John Thomson (1856-1940). The size of the electric charge in an absolute sense, however, was not known.
The American physicist Robert Andrews Millikan (1868-1953) tackled the job. Beginning in 1906, he had followed the course of tiny electrically charged water droplets falling through air, under the influence of gravity, against the pull of a charged plate above. The evaporation of the water confused the results, and in 1911 he began to use tiny oil droplets instead.
Every once in a while, such an oil droplet attached itself to an ion, which Millikan produced by passing X rays through the chamber. With the ion added, the effect of the charged plate above was suddenly strengthened and the droplet would fall more slowly or perhaps even rise. The minimum change in motion was due, Millikan felt, to the addition of a single electronic charge. By balancing the effects of the electromagnetic attraction upward and the gravitational attraction downward, both before and after such an addition, Millikan was able to calculate the charge on a single electron. The figure we now have is sixteen- quintillionths of a coulomb.
For this work, Millikan was awarded the Nobel Prize in physics in 1923.
f"The Eagle Has Landed"
July 21, 1969
MOON, EARTH ORBIT
For centuries people dreamed of what it would be like to go to the moon. They imagined methods of getting there and strange lunar creatures. But on July 21, 1969, it really happened. Astronaut Neil Armstrong first set foot on the moon. "That's one small step for man, one giant leap for mankind," he said.
Armstrong and Edwin "Buzz" Aldrin landed on the moon in the Eagle lunar module. While on the surface they performed various experiments, planted a U.S. flag and explored the area around their landing site. Meanwhile, Michael Collins orbited the moon in the Apollo 11 "Columbia" command module.
This great scientific accomplishment was prompted by a scare. In April 1961, Soviet Cosmonaut Yuri Gagarin became the first man in space. Jolted by this Soviet accomplishment, the United States decided it must catch up.
And it did. Through a series of space programs, from the single seat Mercury capsules to the slightly larger two-man Gemini missions, and finally to the three-man Apollo spacecraft, America gradually obtained the expertise in space exploration necessary for a trip to the moon.
²Samuel's Outstanding Signals
1838 AD
BALTIMORE, MARYLAND
The idea of a telegraph had occurred to a number of people, including American physicist Joseph Henry (1797-1878) and the British inventor Charles Wheatstone (1802-1875). It was just a matter of setting up a long wire and sending electricity through it in pulses by opening and closing a key. Combinations of pulses could be interpreted as letters and words.
What was needed was not so much a scientist, however, as a promoter, who could raise the necessary money to set up a sufficiently long wire, with relays to keep the signal from fading with distance. One such promoter, who had been working on the task since 1832, was the American artist Samuel Finley Breese Morse (1791-1872).
In 1838 he produced a logical list of short and long electric impulses (dots and dashes) for the various letters of the alphabet.
This is called the Morse code to this day. It was the simple combination in Morse code of "... --- ..." that made the letter equivalents, SOS, the international distress call.
Multiplication Becomes Addition
1614 AD
SCOTLAND
Numbers can be written in exponential form. Thus, 2^4 is four twos multiplied together, or 16; while 2^5 is five twos multiplied together, or 32. Nine twos multiplied together, or 2^9, is 512. Since 16 x 32 = 512, we can say that 2^4 x 2^5 = 2^9. Instead of multiplying numbers, we add exponents. This turns out to be a general rule. In the same way, instead of dividing numbers, we can subtract exponents.
If 16 is 2^4 and 32 is 2^5, then 22 must be 2 to some exponent that lies between 4 and 5. If we had the exponents for all numbers listed in a convenient table, multiplication would be reduced to addition, and division to subtraction, with a great saving in time and trouble.
The Scottish mathematician John Napier (1550-1617) spent years working out formulas that would give him appropriate exponents for a great many numbers, and he called them logarithms (from Greek words meaning "proportionate numbers"). In 1614, Napier published his table of logarithms and they at once became useful in all sorts of complicated computations that scientists were forced to make. Nothing better was to come along for over three centuries.
═Space: A Vacuum That's Not
1930 AD
SANTA CRUZ, CALIFORNIA
Three centuries earlier, it had come to be understood that there was a vacuum between the astronomical bodies. It was all too easy then to assume that the vacuum was perfect; that there was really nothing at all once one got outside any atmosphere that might be clinging to the immediate surface of a body.
In 1930, however, the Swiss-born American astronomer Robert Julius Trumpler (1886-1956) noted that the light of the more distant globular clusters was dimmer than would be expected from their sizes. The more distant the cluster, the more marked this departure from the expected brightness. What's more, the more distant the cluster, the redder the light.
The easiest way of explaining this was to suppose that space, even far from sizable bodies, was not a perfect vacuum. (Indeed, a perfect vacuum does not exist and probably cannot exist in the Universe.) There are thin wisps of gas and dust throughout interstellar space, and over vast distances, there is enough of this -- of dust, particularly -- to dim and redden light. By taking the dimming effect of this interstellar matter into account, the size of the Galaxy was shown to be somewhat smaller than Shapley's too-large estimates.
òThe Clue From Drifting Neptune
1846 AD
UNITED KINGDOM
The planet Uranus, discovered by British astronomer William Herschel (1738-1822) in 1781, was naturally observed frequently and carefully by many astronomers. In 1821 the French astronomer Alexis Bouvard (1767-1843) had shown that Uranus's position in the sky had drifted somewhat from the position to be expected if the gravitational influence of the Sun and various planets were taken into account.
One possibility was that an as-yet-unknown planet existed beyond Uranus whose gravitational influence had not been taken into account.
A British astronomer, John Couch Adams (1819-1892), attempted to calculate where such a distant planet might be in the sky based on the discrepancy in Uranus's position. He made some reasonable assumptions as to its mass and its distance from the Sun, and by October 1843, he had a possible position located. Unfortunately, he could not interest the Astronomer Royal, George Biddell Airy, in his work.
Meanwhile, a French astronomer, Urbain-Jean-Joseph Leverrier (1811-1877), was attempting the same task independently, and he ended with a position very similar to that of Adams. He wrote to a German astronomer, Johann Gottfried Galle (1812-1910), and asked him if he would check that region of the sky.
As it happened, Galle had a new map of that portion of the sky, and when he started looking, on September 23, 1846, he found the planet almost at once, for it was fairly bright (as seen through the telescope). It was not on the map. Because of its greenish color, the new planet was named Neptune after the Roman god of the sea. Although Galle actually saw the planet first, the credit for its discovery is divided between Adams and Leverrier. The whole story is usually regarded as the greatest victory that Newton's law of gravitation was to achieve, for a tiny apparent deviation from that law was enough to lead to the discovery of a giant planet.
Later in 1846, the British astronomer William Lassell (1799-1880) discovered a satellite of Neptune, which he named Triton after a son of Neptune (Poseidon) in the Greek myths. It was a large satellite, larger than our Moon, and was the last large satellite to be discovered.
╬The Most Complex Cells
1889 AD
GERMANY
Of all the cells, the nerve cells seem most complex, and of all the organs and systems of organs, the brain and nervous system seem most complex. Moreover, of all the parts of a human body, the brain and nervous system are, or should be, the most interesting, since it is they that make us human. German anatomist Heinrich Wilhelm Gottfried von Waldeyer-Hartz (1836-1921) was the first to maintain that the nervous system was built out of separate cells and their delicate extensions. The delicate extensions, he pointed out, approached each other closely but did not actually meet, much less join, so that the nerve cells remained separate. He called the nerve cells neurons, and his thesis that the nervous system is composed of separate neurons is the neuron theory.
An Italian histologist, Camillo Golgi (1843 or 1844-1926), fifteen years before, had devised a system of staining with silver compounds that brought out the structure of neurons in fine detail. Using this stain he could demonstrate that Waldeyer-Hartz's views were correct. He could show that fine processes did indeed issue from the neurons and that those from one neuron approached but did not touch those of neighboring neurons. The tiny gaps between one neuron and the next are called synapses (oddly enough, from a Greek word meaning "union," which they appeared to be at a casual glance but were not in actuality).
A Spanish histologist, Santiago Ramón y Cajal (1852-1934), improved on Golgi's stain, and by 1889 had worked out the cellular structure of the brain and spinal cord in detail, firmly establishing the neuron theory. For their work on the neuron theory, Golgi and Ramón y Cajal shared the Nobel Prize in medicine and physiology in 1906.
ÉNerves: Not Pipes
1766 AD
SWITZERLAND
From Greek times, nerves had been thought to be hollow tubes that carried some sort of subtle fluid, perhaps in analogy to veins and arteries.
A Swiss physiologist, Albrecht von Haller (1708-1777), dismissed this possibility and decided to reach no decisions on nerves that could not be demonstrated by experiment. His experimental work, which he published in 1766, showed that muscles were irritable; that is, a slight stimulus to the muscle would produce a sharp contraction. He also showed that a stimulus to a nerve would produce a sharp contraction in the muscle to which it was attached. The nerve was the more irritable and required the smaller stimulus.
Haller judged, therefore, that it was nervous stimulation that controlled muscular movement. He also showed that the tissues themselves do not experience a sensation but that the nerves channel and carry the impulses that produce the sensation.
Furthermore, Haller showed that nerves all led to the brain or to the spinal cord, which were thus clearly indicated as the centers of sense perception and responsive action. For all this, he is considered the founder of modern neurology.
«Supernova Watch
1987 AD
LA SERENA, CHILE
The last supernova that had been visible in our own Milky Way Galaxy was one studied by Kepler in 1604. Since then, the nearest supernova had been one spied 2,300,000 light-years away in the Andromeda galaxy, but at the time it was not known to be a supernova and was not carefully studied even with the instruments then available. Since then, the only supernovas to have been noted had been in still more distant galaxies.
In February 1987, however, a supernova was caught in its early explosive stage in the Large Magellanic Cloud. That was not in our own galaxy to be sure, but it was in the galaxy closest to our own, only 150,000 light-years away. The explosion had been heralded by a spray of neutrinos, some of which were caught in recently devised neutrino telescopes. Undoubtedly, as more and better instruments of the sort are built, the sky will be regularly scanned for neutrinos that may herald supernova explosions.
The Magellanic supernova was carefully studied as the light built up and faded and as the nebulosity about it expanded and thinned. In 1988 the expected appearance of a pulsar at its center rotating two thousand times per second was reported.
¬Why Doesn't the Moon Fall?
1669 AD
CAMBRIDGE, ENGLAND
In the years 1665-1666, Newton (1642-1727) was staying at his mother's farm in order to escape the London plague. One evening he saw an apple fall from a tree at a time when the Moon was shining peacefully overhead and began to wonder why the Moon didn't fall. He then thought that perhaps it did, but that it was also moving horizontally and fell at each moment just enough to make up for the curvature of the Earth. Thus, the Moon fell forever but only succeeded in moving around the Earth in one of Kepler's ellipses.
Newton spent considerable time trying to work out how Earth might pull at the Moon as it pulled at the apple, and at what rate the Moon might be falling, but he was not satisfied with his calculations and put them to one side. Some say it was because there was no good determination of the exact size of the Earth at the time; others say it was because he didn't know how to allow for the fact that every bit of Earth was pulling at the Moon from slightly different distances and angles. He needed a mathematical tool that would help him solve that problem.
In 1669 he began working on such a tool, a mathematical technique that came to be called calculus. This was a more versatile technique than anything invented earlier, and science could not do without it these days. Calculus is the beginning of higher mathematics.
Working on the calculus at roughly the same time as Newton was a German mathematician, Gottfried Wilhelm Leibniz (1646-1716). Both he and Newton worked out the technique -- Newton, perhaps, a little sooner -- but Leibniz ended with a better symbolism.
This is not unusual. Frequently two scientists working independently come up with the same answers in response to the same problems. Often the solution is to give them joint credit. Sometimes, however, there are arguments about which scientist was really first, and this may even degenerate into accusations of plagiarism.
That is what happened this time. Exacerbated by national prejudices, English versus German, there was a Homeric battle that poisoned the scientific community for years without ever settling anything. Today, Newton and Leibniz are given joint credit for the calculus.
IIt Can Set a Line o' Type
1884 AD
DETROIT, MICHIGAN
Ever since the invention of printing in 1454, advances had been made in the speed with which it could be carried through. The greater the speed, the more printed matter would be produced, the more would be read, and the more would be desired, especially as literacy increased the world over.
One bottleneck, however, was the setting of type. Plucking out an individual letter and setting it in line was time-consuming.
In 1884 a German-born American inventor, Ottmar Mergenthaler (1854-1899), patented a machine that, when directed by an operator at a keyboard, could set a whole line of type at one time. It was therefore called a Linotype machine. For the next three-quarters of a century it was a mainstay of publishing -- especially newspapers, which increasingly had to be turned out steadily and in quantity.
╧The First Nuclear Reactor
1942 AD
CHICAGO, ILLINOIS
The idea advanced in 1942 by Hungarian-born physicist Leo Szilard (1898-1964) for a nuclear chain reaction could not be made practical. Once the Manhattan Project had been put in motion, Italian-born American physicist, Enrico Fermi (1901-1954) was placed in charge of producing such a chain reaction. Uranium and uranium oxide were piled up in combination with graphite blocks in a structure called an atomic pile. Neutrons colliding with the carbon atoms in graphite did not affect the carbon nuclei but bounced off, giving up their energy and moving more slowly as a result, thus increasing their chance of reacting with uranium- 235.
Making the pile as large as possible made it more likely that neutrons would strike uranium-235 before blundering out of the pile altogether and into the open air. The necessary size was the critical mass. Naturally, the more enriched in uranium-235 the pile was, the smaller the critical mass needed to be.
Cadmium rods were inserted into the pile, because cadmium would soak up neutrons and keep the pile from becoming active prematurely. When the pile was large enough, the cadmium rods were slowly withdrawn and the number of neutrons produced slowly increased. At some point, the increase would reach the level where more were being produced than were being harmlessly consumed by the cadmium. At that time the nuclear chain reaction would begin and the whole thing would go out of control in a moment.
What stopped that from happening was that some neutrons didn't come out of the bombarded nuclei at once. In other words, after the pile went critical, there was a slight pause before the delayed neutrons were emitted and everything went awry. During that pause, the cadmium rods could be shoved in again.
At 3:45 P.M. on December 2, 1942, in the squash court of the University of Chicago, the chain reaction became self-sustaining and was choked off. The atomic age had begun. The atomic pile was the first nuclear reactor.
σThe Rock Oil Revolution
1859 AD
TITUSVILLE, PENNSYLVANIA
Petroleum (from Latin words meaning "rock oil"), sometimes called simply oil, is a complex mixture of hydrocarbons, formed, it is believed, from the fat content of myriads of microorganisms in the distant past.
In the Middle East, where petroleum is particularly common, some was found even on the surface. There the smaller molecules evaporated, leaving behind a tarry substance variously called pitch, bitumen, and asphalt.
This was used in waterproofing. From pitch one could also sometimes extract a flammable liquid called naphtha (from a Persian word meaning "liquid"), which could be used in lamps. There was a limit to what could be obtained on the surface, however. It was also possible to dig for it. Two thousand years before, the Chinese had dug for brine and occasionally obtained oil.
An American railway conductor, Edwin Laurentine Drake (1819-1880), had invested in a firm that gathered oil for medicinal purposes, from seepages near Titusville, Pennsylvania. It occurred to Drake, who knew about the brine- drilling, that oil could be drilled for as brine was.
He studied drilling methods and, in 1859, set about using those methods at Titusville. He drilled 69 feet into the ground and, on August 28, struck oil. He had drilled the first oil well, which was soon producing 400 gallons per day. Other drillings followed, and other oil wells. The first consequence of this was that kerosene could be obtained in great quantities from petroleum, and the kerosene lamp became almost universal in the United States and elsewhere. Kerosene served to replace whale oil and to cut down somewhat on the carnage that humanity was visiting on those inoffensive animals.
Much more than that, however, lay in the future.
These Chemicals Stick Together
1815 AD
FRANCE
Joseph Louise Gay-Lussac (1778-1850) worked carefully with the poisonous gas hydrogen cyanide. In 1815 he discovered a related poisonous gas, cyanogen.
He went on to show that the carbon-nitrogen combination, or the cyano group, was very stable. In chemical changes, the two bound atoms tended to be transferred as a unit. Relatively tightly bound units that maintained their integrity through various chemical changes came to be called organic radicals.
This represented a major step forward in the understanding of organic chemistry; that is, the study of those chemicals and chemical changes characteristic of organisms.
sOrion: A Cloud of Gas
1864 AD
SPACE
Some patches of nebulosity, including the Milky Way itself, had turned out to be clusters of faint stars. A number of Messier objects -- nebulas named after French astronomer Charles Messier (1730-1817) -- had turned out to be globular clusters of stars. Was any nebulosity what it appeared to be -- simply a cloud of gas?
In 1864 English astronomer William Huggins, studying the Orion nebula, found that its spectrum was typical of what would be expected of a luminous gas. It is, indeed, a large cloud of gas (though we know today that stars are embedded in it and that they are what heat the gas to luminosity.)
÷Punching Holes in the Ozone
1985 AD
ANTARCTICA
In 1985 a hole in the ozone layer over the Antarctic was detected by the British Antarctic survey, and the ozone concentration elsewhere was abnormally low. This was taken as disturbing confirmation of the deleterious effect of chloro\fluoro\carbons on ozone.
Chloro\fluoro\carbons, introduced in 1930 by American chemist Thomas Midgley, Jr. (1889-1944), were first used in air-conditioning and later in spray cans. The compounds contained chlorine and fluorine atoms attached to a carbon skeleton and seemed absolutely safe.
As such chemicals were released into the air by spray cans and eventually leaked out of air-conditioning units, they did not accumulate in such quantities as to present direct difficulties for any living organism.
On the other hand, some chloro\fluoro\carbons inevitably drifted upward into the atmosphere and there they encountered the ozone layer. In 1974 two American scientists, F. Sherwood Rowland and Mario Molina, pointed out that such chlorofluorocarbons had the potential for destroying the ozone layer, even if they were present in comparatively small amounts. And indeed, in recent years the ozone layer has been observed to be thinning.
As the ozone layer thins, more energetic ultraviolet light from the Sun will be able to reach Earth's surface, causing increases in the incidence of such problems as skin cancer and cataracts. Worse yet, the ultraviolet may be deadly to soil bacteria and ocean plankton, with incalculable effects on Earth's ecological balance.
NKeeping the Pace
1957 AD
UNIVERSITY OF MINNESOTA
The heart beats regularly, speeding up when exertion or emotion increases the oxygen requirements of the body and slowing down again in repose. For half a century, it had been known that a special patch of cells in the heart initiated the beat, and the patch was called, popularly, the pacemaker. When the pacemaker was diseased or damaged, the heartbeat could not be maintained properly and death might ensue.
Then an artificial pacemaker was devised that used a regular electrical pulse to initiate the heartbeat. At first such things were so bulky they had to be carried outside the body. The first pacemaker that was compact enough to be inserted under the skin in the patient's chest was devised in 1957 by the American physician Clarence Walton Lillehei. Pacemakers are now common among the elderly population.
½Pascal's Costly Calculator
1649 AD
FRANCE
In 1642 the French mathematician Blaise Pascal (1623-1662) invented a calculating machine that could add and subtract. It had wheels that each had 1 to 10 marked off along its circumference. When the wheel at the right, representing units, made one complete circle, it engaged the wheel to its left, representing tens, and moved it forward one notch.
With such a machine, as long as the correct numbers were entered into the device, there was no possibility of a mistake.
He patented the final version in 1649, but it was a commercial failure. It was too expensive, and most people continued to add and subtract on their fingers, on an abacus, or on a sheet of paper.
▓Pasteur Stops Whines, Saves Wine
1856 AD
PARIS, FRANCE
In 1856 France's wine industry was in a bad way. Wine often went sour as it aged, and millions of francs were lost. French chemist, Louis Pasteur (1822-1895) undertook the task of investigating the problem.
He studied samples of wine under the microscope and found that, when wine aged properly, it contained yeast cells that were spherical globules. Wine that was souring contained elongated yeast cells. He decided there were two types of yeast cells, one of which created lactic acid.
He also decided that the only solution to the problem was to kill the yeast cells, good and bad alike, after the alcohol had formed but before the acid had a chance to form. The wine should be heated gently at about 50° C and then stoppered and left to age without the influence of yeast.
The vintners were horrified at the suggestion, but they were desperate enough to try it, and they found that it worked. The process of gentle heating was called pasteurization, and it was eventually applied to milk, too, to prevent diseases that might otherwise be spread by its contamination. This episode turned Pasteur's attention to the world of microorganisms, with enormously important results.
&Stomach Calling Pancreas!
1902 AD
RUSSIA
The pancreas begins to secrete its digestive juice as soon as the acid food contents of the stomach enters the small intestine. How does the pancreas "know" that food, requiring digestion, is making its appearance? The natural assumption is that the entering food stimulates a nerve that in turn stimulates the pancreas. The Russian physiologist Ivan Petrovich Pavlov (1849-1936) suggested that this was so.
Two British physiologists, Ernest Henry Starling (1866-1927) and his brother-in-law, William Maddock Bayliss (1860-1924), tested the matter. They cut all the nerves leading to the pancreas -- yet it still performed on cue.
They then discovered that the lining of the small intestine secreted a substance (which they named secretin) under the influence of stomach acid. It was this secretin that stimulated the pancreatic flow. In short, then, Starling and Bayliss had discovered that it was possible for chemical messages as well as nerve messages to exist in the body.
Eventually other chemical messengers were discovered and Starling suggested they be called hormones, from Greek words meaning "to rouse to activity." Secretin was the first hormone to be recognized as such, but epinephrine, isolated by American pharmacologist John Jacob Abel (1857-1938), turned out to be a hormone, also.
\The Wonderful Accident
1928 AD
LONDON, ENGLAND
Some discoveries are made by accident. In 1928 Scottish bacteriologist Alexander Fleming (1881-1955), who had discovered lysozyme, left a culture of staphylococcus germs uncovered for some days. He was through with it, actually, and was about to discard the dish containing the culture when he noticed that some specks of mold had fallen into it. Around every speck, the bacterial colony had dissolved away for a short distance.
Bacteria had died and no new growth had invaded the area. Fleming isolated the mold and eventually identified it as one called Penicillium notatum, closely related to ordinary bread mold. He decided that it liberated some compound that, at the very least, inhibited growth, and he called the substance penicillin.
Fleming tested the mold on various types of bacteria and found that some were affected and some were not. Human cells were not affected. He did not go further, and it was to be over a decade before scientists returned to the problem. Nevertheless, for this discovery, Fleming received a share of the Nobel Prize for medicine and physiology in 1945.
ïHow to Grow Viruses
1948 AD
HARVARD UNIVERSITY, CAMBRIDGE
A great many of the advances in the fight against bacterial infection over the previous three-quarters of a century had resulted from the ability to grow pure bacterial cultures in the laboratory. This meant the bacteria could be studied easily and methods for slowing or stopping their growth could be developed.
Viruses, however, grow only within living cells, and working with organisms is much slower and less certain than working with Petri dishes. For this reason, viral diseases were far more difficult to fight than bacterial diseases.
Of course one needn't grow the viruses in adult organisms. They could be grown in the developing embryos in chicken eggs, or in those same embryo cells mixed with blood. The trouble was that although viruses would grow there, so would bacteria, and the bacteria would mask the viruses.
Once penicillin became available, however, it could be added to the chicken embryo broth. This prevented the growth of bacteria but did not affect the viruses. The American microbiologist John Franklin Enders (1897-1985) developed this technique in 1948, and it became useful in searching for ways to fight viral diseases, notably poliomyelitis (infantile paralysis). For this work, Enders, along with his colleagues Thomas Huckle Weller (b. 1915) and Frederick Chapman Robbins (b. 1916), shared the Nobel Prize for medicine and physiology in 1954.
GPhonograph: The Wavering Track
1877 AD
MENLO PARK, NEW JERSEY
In 1876 Edison had opened the first industrial research laboratory, at Menlo Park, New Jersey. In 1877, the same year in which he improved the telephone mouthpiece in a crucial manner, he also made what he always said was his favorite invention -- the phonograph (from Greek words meaning "sound-writing").
He put tinfoil on a cylinder, set a free-floating needle skimming over it as the cylinder turned, and connected a source that would carry sound waves to the needle. The needle, vibrating in time to the sound waves, impressed a wavering track on the tin. Afterward, following that track, the needle reproduced the sound waves in a form that was a bit distorted but recognizable.
We all know what the phonograph, and its much improved descendants, have done to bring music (good and bad) into the home.
îPower From Light
1954 AD
WASHINGTON DC
Photovoltaic cells continued to be improved, and eventually some with efficiencies of up to 30 percent appeared. As efficiency rose and the cost of manufacture fell, it seemed the time might come when electricity could be manufactured directly out of sunlight. If the Sun were used in that fashion, we would never run out of the supply and there would be no chemical pollution.
0Pi: It's Never Quite Round
1596 AD
NETHERLANDS
The ancient Greeks had their favorite problems and one of them was squaring the circle; that is, given a circle of a particular size, to construct a square with the same area. The rules were that you could only use a straight- edge (something that would draw straight lines) and a compass (something that would draw circles) and you had to do it in a finite number of steps.
Unfortunately, they could never solve that problem.
In working with it, though, they got involved with the ratio of the circumference of a circle to its diameter, a ratio that we now refer to as pi (one of the Greek letters). Anyone can measure the diameter and then run a piece of string around the circumference, straighten it, and measure that, too. It turns out that the circumference (for any circle at all) is just a little over 3 times as long as the diameter. But what is the ratio exactly?
There are geometric ways of trying to get the exact ratio, and Greek scientist Archimedes (ca. 287-212 B.C.) had gotten a figure of about 3.142. Better values were obtained in later centuries until, in 1596, the Dutch mathematician Ludolf van Ceulen (1540-1610) obtained a value of pi to twenty decimal places. (Later in life, he got it to thirty-five decimal places.)
Even that didn't give an exact value, but it was so nearly exact that no reasonable computation involving pi would need a more exact value. (In Germany, pi is still sometimes called Ludolf's number.) Since then, pi has been obtained to a vastly greater number of decimal places, but even so there is no exact figure.
WBarbara's Sleeping Pills
1863 AD
BERLIN, GERMANY
In 1863 the German chemist Adolf von Baeyer (1835-1917) discovered barbituric acid. (There is a story that he named it for a girlfriend of the moment whose name was Barbara.) Barbituric acid is the parent substance of a family of compounds known as barbiturates, which are well known today for their use in sleeping pills.
e Galileo Drops The Ball
1589 AD
PISA, ITALY
Aristotle had stated that the heavier an object was, the more rapidly it would fall. It seemed reasonable to say so. Why shouldn't a heavier body fall more rapidly? It is clearly being attracted to Earth more strongly, or it wouldn't be heavier. Furthermore, anyone who watches a feather, a leaf, and a stone falling will see at once that the stone falls faster than the leaf, which in turn falls faster than the feather.
The trouble is that light objects are impeded by air resistance, and in order to avoid that one should consider only relatively heavy objects. Thus, if one observes the falling of a rock that weighs 1 pound and another that weighs 10 pounds, air resistance is insignificant in either case. Do we then see that the 10-pound rock nevertheless falls faster than the 1-pound rock?
In 1586, Dutch mathematician Simon Stevin (1548-1620) is supposed to have dropped two rocks at the same time, one considerably heavier than the other, and showed that they struck the ground at the same time. Later accounts said it was Galileo who demonstrated this by dropping different weights simultaneously from the Leaning Tower of Pisa. Both stories may or may not be true.
What is certain, though, is that in 1589 Galileo started a series of meticulous tests with falling bodies. Such bodies fall too rapidly to make it easy to measure the rate of fall accurately, especially since no accurate way of measuring short periods of time had yet been worked out.
Galileo therefore allowed balls to roll down inclined planes. The more nearly level the plane, the more slowly the balls moved under the pull of gravity and the more easily their rate of fall could be measured by primitive methods such as water dripping out of a small hole. In this way Galileo found it quite easy to show that as long as the balls were heavy enough to be relatively uninfluenced by air resistance, they rolled down an inclined plane at the same rate.
He was also able to show that the balls rolled down the inclined plane with a constant acceleration -- that is, they gained speed with time at a constant rate, under the constant pull of gravity.
This settled another important point. Aristotle had held that in order to keep a body moving, a force had to be continually applied. This again seemed to fit observation. If an object were sent sliding across a floor, it would quickly slow to a stop. To keep it moving, you would have to keep pushing.
For this reason, it was felt that the planets in their eternal movement about the Earth had to be continually pushed by angels.
Galileo's observations showed that a constant push was not necessary to keep an object moving, if friction was removed. If a constant pull was exerted by gravity, for instance, an object moved with a constantly increasing speed. Consequently, no angels were required to keep the planets moving.
Galileo's experiments on moving bodies were so impressive that, even though he was not the first to conduct experiments -- French scholar Peter Peregrinus (13th century) had done so more than three centuries before -- he is usually given credit for having founded experimental science.
»
Planck's Grainy Energy
1900 AD
GERMANY
German physicist Gustav Robert Kirchhoff (1824-1887) had pointed out that a black body (one that absorbed all electromagnetic radiation that fell on it) would radiate at all wavelengths if heated. Thus, a hollow body with a small hole in it would absorb all the radiation that entered through the hole, for virtually none of it would be reflected and find its way out again. If such a body was heated, radiation would therefore emerge from the hole at all wavelengths, with very little at the extremes and with a peak at some intermediate value. The higher the temperature, the shorter the wavelength of the peak value.
A number of physicists tried to work out mathematical equations for the distribution of wavelengths in such black body radiation. British physicist John William Strutt, Lord Rayleigh (1842-1919) and Wien both advanced equations in 1900, but Rayleigh's worked well only for the long-wavelength half, and Wien's only for the short-wavelength half. Neither one could work out an equation that gave the distribution across the board.
Then a German physicist, Max Karl Ernst Ludwig Planck (1858-1947), produced an equation that did just that. In order to derive that equation, he had to assume that energy was given off not continuously but in discrete pieces, and that the size of the piece was inversely proportional to the wavelength. Thus, since violet light had half the wavelength of red light, violet light would be delivered in pieces that were twice the size, and therefore twice the energy content, of red light.
Planck called the bits of energy quanta (singular, quantum, a Latin word meaning "how much?"). He worked out the relationship between energy and wavelength (or energy and frequency, since frequency is 1 divided by the wavelength), making use of a very small value called Planck's constant, which represents the "graininess" of energy. Since Planck's constant is exceedingly small, energy has a very fine grain indeed, and it is not noticeable in most circumstances, so that the laws of thermodynamics could be deduced as though energy were a continuous fluid without grain. The problem of black body radiation was the first in which the graininess had to be taken into account.
There was no evidence, at first, for the existence of quanta, except for the fact that it made the equation for black body radiation possible. Even Planck himself suspected that quanta might be only a mathematical device that had no physical meaning.
Nevertheless, the quantum theory, as it is now called, proved so fundamental that all physics prior to 1900 is called classical physics and all physics after 1900 modern physics. For his work, Planck received the Nobel Prize for physics in 1918.
┤Planet X and Uranus
1930 AD
FLAGSTAFF, ARIZONA
Neptune had been discovered by British astronomer John Couch Adams (1819-1892) and French astronomer Urbain-Jean-Joseph Leverrier (1811-1877) because Uranus was not moving in its orbit exactly as it should, so that the gravitational field of a more distant planet was suspected.
Neptune's presence reduced but did not entirely wipe out the discrepancies in Uranus's orbit, and some astronomers thought that a still more distant but fairly large planet might exist beyond Neptune.
Percival Lowell, who was so enthusiastic about Martian canals, was also enthusiastic about this "Planet X" and spent much of his time calculating its possible orbit and then searching for it. He died without having found it, but at Lowell Observatory, which he had founded, the search went on.
The American astronomer Clyde William Tombaugh (b. 1906) continued the search methodically. His technique was to take two pictures of the same small part of the sky on two different days. Each of these would show from 50,000 to 400,000 stars. Despite all those stars, the two plates would be identical if the spots of light were stars, and only stars. If the two plates were projected on a screen in rapid alternation, none of the stars would seem to move. If one of the "stars" was really a planet, however, one that had moved against the starry background during the interval between photographs, as the plates were alternately thrown upon the screen, that one object would seem to dart back and forth.
On February 18, 1930, Tombaugh found such a flicker in the constellation Gemini. From the smallness of the shift, the object had to be moving very slowly and must therefore lie beyond Neptune. On March 13, 1930, the seventy-fifth anniversary of Lowell's birth, the discovery was announced. The new planet was named Pluto, first because that god of the nether darkness was appropriate to a planet swinging farthest out from the light of the Sun, and second because the first two letters were the initials of Percival Lowell.
In time, though, Pluto turned out to be a small planet incapable of influencing Uranus's orbit measurably. The possibility of another large planet beyond Neptune therefore remains to this day.
ΩAqueduct to the Past
1592 AD
POMPEII, ITALY
The cities of Pompeii and Herculaneum, near the base of Mt. Vesuvius in southern Italy, had been buried under lava and ash when the volcano unexpectedly erupted on August 24, 79.
For fifteen centuries they remained hidden, until an Italian engineer, Domenico Fontana (1543-1607), began tunneling under a hill in order to establish an aqueduct. The ruins were discovered in the process.
This brought the realization that part of the past was actually preserved for investigation in the present. Excavation for the deliberate purpose of studying the past did not start for another century, but the subject matter of the study was known to be waiting, so this discovery might be viewed as the beginning of modern archaeology.
FIt Just Feels True
1742 AD
RUSSIA
A mathematician who thinks some statement seems true but can't prove it's true may then advance it as a conjecture.
The most famous conjecture is one made by a German mathematician who worked in Russia, Christian Goldbach (1690-1764).
To explain it, we begin by saying that a prime number is any number greater than 1 that can only be divided by itself and 1. There are an infinite number of primes. The first few are 2, 3, 5, 7, 11, 13, 17, 19, and 23.
It seemed to Goldbach that any even number greater than 2 could be expressed as the sum of two primes (sometimes in more than one way). Thus, 4 = 2 + 2; 6 = 3 + 3; 8 = 5 + 3; 10 = 5 + 5; 12 = 7 + 5; 14 = 7 + 7; 16 = 11 + 5; 18 = 13 + 5; 20 = 13 + 7; 22 = 11 + 11; 24 = 13 + 11; 26 = 13 + 13; 28 = 23 + 5; 30 = 23 + 7; 32 = 19 + 13; 34 = 17 + 17; 36 = 23 + 13; 38 = 19 + 19; 40 = 23 + 17; 42 = 23 + 19; and so on.
No mathematician has ever found an even number higher than 2 that could not be expressed as the sum of two prime numbers. Every mathematician is convinced that no such number exists and that Goldbach's conjecture is true. However, no mathematician has ever been able to prove the conjecture.
But that sort of thing is the excitement of mathematics and of science generally. We shall never run out of problems, and some will always remain incredibly tantalizing.
╔The Colors in White
1666 AD
CAMBRIDGE, ENGLAND
The English scientist Isaac Newton (1642-1727), curious about light, conducted a series of crucial experiments in 1665 and 1666. He allowed a beam of light to pass through a prism (a triangular piece of glass) and then fall on a white wall.
What emerged was a band of colors, the least bent portion of the light being red, and then following, in order, orange, yellow, green, blue, and violet, each merging gradually into the next. Were the colors produced by the glass? No, for when Newton passed the light that had emerged from the prism through a second prism oriented in the opposite direction, all he got was white light. The colors had recombined. This meant that light had to be looked upon in a totally new way. It had always been assumed that white light was "pure" light and that color was introduced as an impurity through the effect of material substances on the light.
Newton's work made it clear that color was an inherent property of light and that white light was a mixture of different colors. Matter affected color only by absorbing some kinds of light and transmitting or reflecting others. Exactly what it was that made light assume different colors was not yet clear, however.
Creations and Falls
1812 AD
PARIS, FRANCE
French anatomist Georges Cuvier (1769-1832) found important and interesting fossils. In 1812 he reported the fossil remains of a creature that clearly must have had wings and been able to fly but whose skeleton showed it to have been a reptile. It was named pterodactyl, from Greek words meaning "wing-finger," because the membrane of its wing was stretched out along one elongated finger.
Cuvier could see that fossils represented creatures that were extinct and that the deeper the stratum and the older the remains, the less the fossils resembled modern organisms. Nevertheless, he couldn't accept the idea of evolution.
Instead, in a book entitled Inquiry into Fossil Remains, published in 1812, he advanced the notion that there had been numerous creations, each one ended totally by some catastrophe and followed by a new creation of life closer to that of the present.
This view, called catastrophism, is usually considered the opposite of James Hutton's uniformitarianism, and for a long time the two were considered mutually exclusive. However, it is quite possible that Earth's history shows periods of uniformitarianism interspersed by episodes of catastrophism (though none of the catastrophes, so far, seem to have been complete).
Cuvier was the first to go into detail on the appearances of ancient forms of life, and he attempted to classify them, as far as possible, by using the same system used for living species. In this way, he is considered to have founded paleontology, the study of ancient extinct forms of life.
ⁿ Egypt Starts Big Building Fad
2650 BC
GIZA, EGYPT
Thanks to the Nile, the Egyptians were able to grow a surplus of food so that many could devote themselves, for at least part of the year, to other tasks. That meant that the Egyptian rulers could put the Egyptian people to work on public projects designed to show the greatness of their rulers and, through them, of the nation and the people. The projects would also serve as memorials to that greatness to future generations.
Thus the Egyptian rulers built elaborate houses (or palaces, as we now call them). Indeed, the ruler was referred to as pharaoh, which is the Greek version of an Egyptian word meaning "big house." (This is similar to our present habit of saying "the White House" when we mean the president.) It was customary for the important citizens of the nation to build themselves elaborate burial tombs, since Egyptian religion dealt in detail with life after death, and it was felt that, to insure immortality, the body had to be preserved. The tombs were oblong objects called mastabas. (Nowadays, to insure the immortality of our presidents, we build colossal presidential libraries.)
In about 2686 B.C., when Djoser, the second king of the Third Dynasty came to power, he decided to build a particularly elaborate tomb as a memorial to his greatness. He had a counselor named Imhotep who supervised the building of six mastabas of stone, one on top of the other, each smaller than the one below. The result was basically pyramidal in shape, but it was set back periodically as modern skyscrapers sometimes are. Because these setbacks were like steps a giant would use in climbing to the top, the structure is called the Step Pyramid. The base is an oblong about 400 feet by 350 feet, and the top is almost 200 feet high.
The Step Pyramid was the first large stone structure ever built and is the oldest structure built by humans that remains substantially intact today. The Step Pyramid set a fashion, and for a couple of centuries afterward the pharaohs kept the people busy in their spare time building more and more elaborate pyramids. Larger and larger stones were used, and the climax came when the Pharaoh Khufu (Cheops to the Greeks) supervised construction of the Great Pyramid, the largest of all, in about 2530 B.C.
When that pyramid was finished, its square base was 755 feet on each side, so that it covered an area of 13 acres. The four sides sloped upward evenly (for the notion of steps had been abandoned) to a point 481 feet high. It was solidly composed of slabs of rock -- 2,300,000 of them, it is estimated, with an average weight of 2-1/2 tons apiece. Each had to be brought some 600 miles, by water, of course, from quarries far up the Nile.
In among these rocky slabs were passages leading to a chamber near the center of the huge pile, which was to contain the king's coffin, his mummy, and his treasures after his death.
The fad for such large, vainglorious structures did not persist for long. They took too much time and too much work even for Egypt. The urge to build big objects, some useful, some symbolic, some vainglorious, has never left humanity, however. Some of the medieval cathedrals finally surpassed the pyramids in height (after 3,500 years or so) and today, of course, we have our skyscrapers, our huge bridges and dams, and so on.
▄Irrational But Not Crazy
520 BC
SAMOS, GREECE
The Greek philosopher Pythagoras (ca. 580-ca. 500 B.C.) believed that whole numbers, including fractions, since they are ratios of whole numbers, were the basis of the Universe. Thus, 3/4 is the ratio of 3 to 4. If you begin with 3 pies and divide them equally among 4 people, each person gets 3/4 of a pie. Whole numbers and fractions together make up the rational numbers (those that can be expressed as ratios), and it is easy to suppose that rational numbers are all that exist.
However, suppose you have a right triangle with each side equal to 1 unit. What is the length of the hypotenuse? The answer can be obtained by remembering that the square of the hypotenuse is equal to the sum of the squares of the sides. This was long known, but Pythagoras worked out a good proof and it is called the Pythagorean theorem as a result.
The square of each side is 1, so the square of the hypotenuse is 2, and the length of the hypotenuse is the square root of 2, or that number which, when multiplied by itself, equals 2. The number 7/5 is nearly right, since 7/5 x 7/5 = 2.04. The number 707/500 is even closer, since 707/500 x 707/500 is a little over 1.999.
It can be shown quite easily, just the same, that there is no fraction, no fraction at all, however complicated, that when multiplied by itself gives exactly 2. The square root of 2 is therefore not a rational number. It is an irrational number, and as it turns out, there are an infinite number of such irrationals.
Hertz Discovers Radio Waves
1888 AD
GERMANY
In 1887, when German physicist Heinrich Rudolph Hertz (1857-1894) was performing the experiments that gave him the first glimpse of a photoelectric effect, he expected that the oscillating current he was working with would produce an electromagnetic wave. Each oscillation should produce a wave, and the wave should be very long. After all, since light travels at a bit over 186,000 miles per second, a wavelength formed in an oscillation of a mere hundred-thousandth of a second will still be nearly 2 miles long. In 1888, he actually observed such waves.
Hertz used, as a device for detecting the possible presence of such long- wave radiation, a simple loop of wire, with a small air gap at one point. Just as the current in his first coil gave rise to radiation, so the radiation produced ought to give rise to a current in the second coil. Sure enough, Hertz was able to detect small sparks jumping across the gap in his detector coil.
By moving his detector coil to various parts of the room, Hertz could tell the shape of the waves by the intensity of the spark formation and could calculate a wavelength of 2.2 feet. This is a million times the size of a wavelength of ordinary light. He also managed to show that the waves were electromagnetic in nature. At first these long-wave radiations were called Hertzian waves, but later the name radio waves came into use instead.
In this way, Hertz verified the usefulness of Maxwell's equations and showed that light was only a tiny section of the electromagnetic spectrum.
Reflections on Venus
1961 AD
GOLDSTONE TRACKING STATION (BARSTOW, CALIFORNIA)
Fifteen years ago, microwaves had been reflected from the Moon. That had been comparatively easy. By 1961 the technique had advanced to the point where microwaves could be sent out to Venus, a hundred times as far away as the Moon. This was done, and reflections were received by five different groups, one Soviet, one British, and three American.
The microwaves traveled through space at the speed of light, and from the time measured between the emission of the original beam and the detection of the reflection, the distance of Venus and therefore the general scale of the Solar System could be determined much more accurately than had been possible from observations of the asteroid Eros.
It took a long time for our knowledge of Venus to advance to this point. Initially the Greeks, from whom we get so much knowledge, were not as advanced in astronomy as the Babylonians were. They knew the evening star, a bright planet that appeared in the western sky after sunset, and they called it Hesperos (the Greek word for "evening"). There was also a morning star, a bright planet that appeared in the eastern sky before sunrise, and they called it Phosphoros (the Greek word for "light-bring-er," because once it appeared, the Sun was not far behind).
In 520 B.C. Pythagoras (ca. 580-ca. 500) was the first Greek to realize the two were the same object, since when the evening star was in the sky there was no morning star and vice versa. (He is supposed to have traveled in Babylonia, and he may have learned this there.) About 500 B.C., he named this single planet, which swung from one side of the Sun to the other and back again, Aphrodite, after the Greek goddess of love and beauty. The Romans (and we) called it by their equivalent, Venus.
ÿSap and Blood
1733 AD
ENGLAND
English physiologist Stephen Hales (1677-1761) had studied the flow of sap in plants and went on to study the flow of blood in animals, measuring the rate of flow in different portions of the circulatory system. Most important of all, he was the first person to measure blood pressure, albeit in a crude way. He described his work in this field in a book entitled Hemostaticks, published in 1733.
vElectricity From the Atom
1942 AD
CHICAGO, ILLINOIS
Even before the first fission bomb had been exploded, a controlled nuclear reactor (although a very inefficient one) had been set up in Chicago in 1942. Its only function was to show that a fission bomb was possible.
Efforts were later made, however, to devise nuclear reactors efficient enough to serve as reasonable sources of controlled energy for peaceful uses. The fissioning uranium or plutonium would liberate heat at a moderate rate, and this heat would turn water into steam, which would turn a turbine and produce electricity.
Naturally, methods had to be devised to slow the fission reaction if it showed signs of proceeding too quickly and producing enough heat to result in a meltdown. A controlled nuclear reactor could not explode, since it was not enclosed strongly enough to build up the kind of heat and force that would lead to an explosion. It would, however, be capable of releasing a surge of nuclear radiation into the environment, so the pressure for safe operation was therefore strong.
The first nuclear reactor built to produce electric power for civilian use was put into action in the Soviet Union in June 1954. It was a very small one. Larger reactors were produced in Great Britain and in the United States soon after, and eventually they were distributed around the globe and began to contribute substantially to the world's energy supply, particularly in France and the Soviet Union.
Controlled reactors also came into use in another way. Submarines throughout both world wars had remained vulnerable because they had to surface periodically to recharge their batteries. Under the driving force of the Polish-born American naval officer Hyman George Rickover (1900-1986), a plan developed to equip American submarines with atomic reactors, which would require no recharging and could keep a submarine submerged for months at a time. The first nuclear-powered submarine, the Nautilus, was launched in January 1954.
Some nuclear-powered surface vessels were eventually built by the Soviet Union and the United States, but except for submarines, nuclear-powered forms of transportation did not catch on.
∞Bringing in the Sheaves Quicker
1834 AD
CHICAGO, ILLINOIS
Agriculture had always been a labor-intensive occupation, particularly at harvest time, when there was often a shortage of hands to reap and gather the grain.
Attempts were therefore made to devise a mechanical reaper, and the one that finally proved successful was built by an American inventor, Cyrus Hall McCormick (1809-1884). He first built what came to be called the McCormick reaper in 1831, and he secured a patent for it in 1834. It wasn't immediately successful, but McCormick pushed it with great pertinacity, and little by little, it took hold, particularly in the vast grain fields of the American Midwest.
This began a whole series of mechanical inventions that gradually reduced the number of laborers that had to work the land to produce food, until finally, in a thoroughly industrialized nation such as the United States, a work force of 4 percent of the whole suffices to grow food for itself and for the remaining 96 percent, with enough left over to export.
JBig Red
1664 AD
LONDON, ENGLAND
In 1664 English physicist Robert Hooke (1635-1701) noted a large oval marking on Jupiter that came to be called the Great Red Spot. The name was accurate, for it did seem to be red in color and it was great in the sense of being very large. The entire Earth could be dropped into it without touching its sides.
┴Newton Reflects on Telescopes
1668 AD
UNITED KINGDOM
During the first sixty years of the telescope's use, its lenses curved light by refraction and focused it. In this way, the eye saw the image as brightened and expanded. Such telescopes were refracting telescopes.
Unfortunately, the lenses refracted different colors of light differently and formed a spectrum, so that the images in such telescopes were always blurred by colored rings, red or blue (chromatic aberration). This was minimized by using only the center of the lens and having the light come together only gradually and reach a focus at a considerable distance from the lens, but this meant that telescopes capable of considerable brightening and enlargement had to be long and unwieldy.
English scientist Isaac Newton (1642-1727), through his experiments with light, supposed that one couldn't possibly have a lens without blurring the image with color. He therefore thought of an alternative. Why not use curved mirrors instead of curved lenses, and focus the light by reflection rather than refraction?
Reflection did not produce a spectrum. In 1668, therefore, he built the first reflecting telescope, and thereafter two varieties of telescope were available to astronomers.
.The World's Wet Highways
3500 BC
EGYPT
It is certainly easier to carry heavy loads over water than over land. Water offers much less friction than land does, and there are no permanent unevennesses in it: no rocks, no ridges, no uphill stretches.
In this connection, the Nile was ideal. Not only was it a source of water for rainless Egypt -- not only did its annual flood periodically fertilize the soil -- but its current was gentle and there were no storms. The Nile did not damage and overturn boats as the unruly Tigris in Sumeria did. (The very name of that river is the Greek word for "tiger.")
What's more, the Nile flows almost due north, while the wind is almost always from the north. Therefore a boat can move smoothly down river and, when the time comes to return, a sail can be hoisted to catch the wind and the ship will be blown upstream.
Egypt is not a forest nation, but it had luxuriant stands of reeds (called papyrus) along the river in those days, and the reeds could be used in bundles to build boats. The boats were built to form hollows, so that they would displace more water and carry more weight without sinking. These reed boats were not particularly sturdy, but the gentle Nile did not require sturdy boats. (When Moses was set afloat in the Nile River, he was placed in a little boat -- or ark -- of bulrushes; that is, papyrus.)
Egypt thus had a most convenient form of communication that perhaps accounted for its slowness to adopt the Sumerian wheeled cart. Egypt had scarcely any need for land transportation.
By 3500 B.C. Egyptian boats had begun to ply the Nile, and by 3000 B.C. they were venturing out of the Nile into the Mediterranean, hugging the shore, and making their way past Sinai and Canaan to Lebanon. There they obtained the tree-trunks they lacked in Egypt and brought them back for construction purposes.
Mechanical Slaves
1954 AD
PRAGUE, CZECHOSLOVAKIA
The word robot (from a Czech word for "serf" or "slave") had been invented by the Czech playwright Karel Capek (1890-1938) in his play R.U.R., first staged in Europe in 1920. Since Capek's time, the word has come to be applied to any manufactured device, usually envisaged as humanoid in shape (though it doesn't have to be) and made of metal (though again, it doesn't have to be), which is capable of doing work ordinarily done by human beings.
Although robots were much used in science fiction, the first patent wasn't taken out on a robotic device in real life until 1954. It was the work of the American inventor George C. Devol, Jr., who teamed up afterward with the American entrepreneur Joseph F. Engelberger (b. 1925), who had grown interested in robots as a result of reading I, Robot by Isaac Asimov (1920-1992).
For twenty years they continued to develop patents, but the manufacture of robots that were sufficiently cheap and compact to be used in industry had to await further advances in computers.
tThe Key to Egyptian
1799 AD
EGYPT
While the army of Napoleon Bonaparte (1769-1821) was in Egypt, a French soldier came across a black stone near a town that Europeans called Rosetta. What he found was therefore called the Rosetta Stone.
On the Rosetta Stone was an inscription in Greek dating back to 197 B.C. It wasn't an interesting inscription in itself, but present also were inscriptions in two different forms of Egyptian writing. If, as seemed likely, this was the same inscription in three different languages, then one had an inscription in two forms of Egyptian writing, which at that time no one could read, and a Greek inscription that many scholars could read.
In the next few decades, the Rosetta Stone was studied in order to learn the Egyptian languages, so that from inscriptions and writings left behind by the Egyptians, vast stretches of Egyptian history might come to be understood.
▀Shadow Geometry
1822 AD
FRANCE
The French mathematician Jean-Victor Poncelet (1788-1867) was taken prisoner during Napoléon's invasion of Russia, and during the year and a half he spent in Russia, he meditated on geometry. The fruits appeared in 1822, when he published a book on projective geometry (roughly, the study of the shadows cast by geometric figures). Previously knotty problems yielded easily to the new technique. The book is usually considered to be the foundation of modern geometry.
ΘMovement to Heat
1843 AD
GREAT BRITAIN
Some conservation laws had already been accepted by this time. French chemist Antoine-Laurent Lavoisier (1743-1794) had advanced the law of conservation of mass and before that there had been the law of conservation of momentum.
There were suspicions that energy ought to be conserved also. After all, motion was a common form of energy, and according to Newton, a moving body would move on forever if not affected by an outside force. The energy would not disappear.
In real life, though, a moving body does stop moving after a while because of air resistance or because of friction with the ground. What happens to its energy then? Perhaps it is converted into heat. If so, however, a given amount of mechanical energy should be converted into some fixed amount of heat. Otherwise energy is not conserved.
A British physicist, James Prescott Joule (1818-1889), undertook to check this by experimentation. He expended energy in a variety of ways and measured the amount of heat produced. All his experiments showed that a fixed quantity of work ended up in a fixed quantity of heat. In 1843 he published his results: that 41,800,000 ergs of work produce 1 calorie of heat. This is called the mechanical equivalent of heat. Since 10,000,000 ergs are now called a joule in Joule's honor, we can say that 4.18 joules equal 1 calorie.
This made it appear that there might well be a law of conservation of energy if heat were included among the forms of energy. In fact a German physicist, Julius Robert von Mayer (1814-1878), had presented a figure of the mechanical equivalent of heat in 1842 (one that was far less accurate than Joule's) and deduced from it that a law of conservation of energy existed, but his work did not attract attention.
¿Heavy Alpha, Light Beta
1897 AD
UNITED KINGDOM
The radiations given off by uranium were of more than one kind. Some were deflected only slightly in a direction that indicated them to be positively charged. Some were deflected much more sharply in the opposite direction and were therefore negatively charged. Both had to consist of streams of particles, and the particles of the former were clearly the more massive.
The British physicist Ernest Rutherford (1871-1937) noted this in 1897. He called the massive, positively charged radiation alpha rays, and the lighter, negatively charged radiation beta rays, after the first two letters of the Greek alphabet. Those names have remained in use ever since.
=Salk: Polio Killer
1953 AD
UNIVERSITY OF PITTSBURGH, PENNSYLVANIA
Poliomyelitis (infantile paralysis) was a particularly frightening disease, because when it did not kill, it often paralyzed permanently, leaving people in wheelchairs or even iron lungs. What's more, it often hit young people.
Once the polio virus could be cultured in chick embryos, however, as shown by American microbiologist John Franklin Enders (1897-1985) and his group, it was possible to experiment with it.
Thus the American microbiologist Jonas Edward Salk (b. 1914) tried to kill the virus, so that it would not give rise to the disease, but to leave it sufficiently intact that it would stimulate the growth of antibodies and lead to immunity should a living virus later invade.
First he tried his preparation (Salk vaccine) on children who had recovered from polio, to see if it raised the antibody content. Then in 1953 he dared to try it on children who had not had the disease, to see if antibodies would develop. They did, and within two years mass inoculation had begun. The dread disease became a thing of the past.
5Koch Isolates Bacteria
1876 AD
SILESIA, GERMANY (POLAND)
When an anthrax epidemic struck the cattle in Silesia (eastern Germany), a local physician, Robert Koch (1843-1910), grew interested. In 1876 he located the particular bacterium that caused anthrax in the spleen of infected cattle and transferred it to mice, carrying the infection from mouse to mouse and recovering the same bacilli in the end. More important still, he learned to cultivate the bacteria outside the living body, using blood serum at body temperature.
Then he learned to make use of solid media for growing bacteria -- gelatin, or a complex carbohydrate called agar, which could be obtained from seaweed. When grown in such solid media, the bacteria could not move about easily, and if the bacteria happened to be isolated in one spot, they would, by division and redivision, give rise to a patch of descendant bacteria with no admixture of outside varieties. Bacteria could then be transmitted to animals or allowed to start new cultures with the certainty that only a particular strain of bacteria was being worked with.
In short, Pasteur's germ theory was given practical application by Koch. Koch showed how the causative bacteria could be isolated, then used to produce the disease, then regained from the diseased animal, and finally worked with to find a prevention or cure.
╡Salt: No Molecules, Just Ions
1914 AD
UNITED KINGDOM
Thirty years earlier Swedish chemistry student Svante August Arrhenius (1859-1927) had advanced the notion that electrolytes in solution dissociated into ions. The idea was that a substance such as sodium chloride existed in solid form as a molecule, symbolized as NaCl, but on solution split up into the positively charged sodium ion (Na+) and the negatively charged chloride ion (Cl-).
When the British father-and-son physicists, William Henry (1862-1942) and William Lawrence (1890-1971) Bragg, were studying X-ray diffraction, however, they found that that phenomenon could best be understood if it was supposed that in a solid crystal of sodium chloride there were no intact molecules, merely sodium ions and chloride ions positioned with geometric regularity. Sodium chloride and many other compounds did not exist as molecules in the older sense, then, but as arrays of ions held together by electromagnetic interaction.
µSouth America: Jungle and Empire
1990 AD
SOUTH AMERICA
Notice the vast green stretch in the northeast part of South America. That green is the Amazon Jungle, a huge area of plant and animal life, many of which are found nowhere else in the world.
Unfortunately, there is less and less of this jungle each day as people move into the area and clear the land. Many environmentalists are concerned about the results of this deforestation on the local and global environment.
South America covers 6.8 million square miles and is inhabited by 296 million people. It is the fourth largest continent and has the largest tropical rain forest in the world, the Amazon, which occupies about two fifths of its area. The Amazon contains more plant types than any place on earth and is navigable by oceangoing ships as far north as Iquitos, Peru.
The continent also has the world's highest navigable lake, Lake Titicaca in the Andes, and the Atacama Desert in Chile, one of the driest places in the world.
In the Andes, the Incas founded a great empire centered in Cuzco, Peru that stretched more than 2,500 miles along the west coast of the continent. It was tied together by carefully constructed highways and bridges. In his quest for gold, the Spaniard Francisco Pizarro destroyed the Inca Empire in 1533.
Following the conquests of Pizarro and others, much of South America came under the dominion of Spain, but in the 1800s Simon Bolivar liberated much of the continent. Brazil, once a colony of Portugal, took its own route to nationhood, becoming independent in 1823.
Today, the most highly developed countries in South America are Argentina, Brazil, Uruguay and Venezuela. The continent is rich in such natural resources as farmlands, timber, minerals, copper, gold, lead, tin, zinc and coffee.
¡ Wandering Continents
1912 AD
GERMANY
As soon as the shoreline of South America had been mapped, three and a half centuries before, people had noticed that South America and Africa gave the impression that they would fit together neatly if they were moved together.
In 1912 the German geologist Alfred Lothar Wegener (1880-1930) proposed that Africa and South America had indeed once formed a single landmass, which had broken in two, and that the two parts had then moved apart in a sort of continental drift.
In fact, he suggested that all the continents had originally formed a single mass (Pangaea, Greek for "all-earth") surrounded by a continuous ocean (Panthalassa, Greek for "all-sea"). This large granite mass of Pangaea had broken into chunks that slowly separated, floating on a basalt ocean-floor, and over hundreds of millions of years, produced the pattern of fragmented continents that we now have.
Unfortunately, the notion of granite floating on basalt did not seem a tenable hypothesis, and on the whole, few people took Wegener's notions seriously at the time.
By 1953 it had been known for thirty years that there was a mountain range down the middle of the Atlantic Ocean. Eventually it was understood that this was part of a world-girdling range called the Mid-Oceanic Ridge.
In 1953 the American physicists Maurice Ewing (1906-1974) and Bruce Charles Heezen (1924-1977) discovered that a deep canyon ran the length of the ridge. It was called the Great Global Rift. There were places where the rift came quite close to land: it ran up the Red Sea between Africa and Arabia and skimmed the borders of the Pacific through the Gulf of California and up the coast of the state of California.
The rift seemed to break the Earth's crust into plates tightly joined as though fitted together by a skilled carpenter. They were therefore called tectonic plates, from a Greek word for "carpenter." The study of the evolution of the Earth's crust in terms of these plates is called plate tectonics, and it has totally revolutionized geology, explaining a great deal that had been mysterious before.
There are six large tectonic plates and a number of smaller ones, and it is along the boundaries of the plates that Earth's quakes and volcanoes seem to be concentrated. One plate, which includes most of the Pacific Ocean, and with boundaries of the eastern coast of Asia and the western coast of America, accounts for about 80 percent of the earthquake energy released on Earth.
⌡Skylab: Mini Space Station
1973 AD
CAPE CANAVERAL, FLORIDA
The first American orbiting object that might be considered a space station was Skylab. It was 118 feet long and was launched into orbit on May 14, 1973, about 270 miles above Earth's surface. On May 25, three astronauts were carried to Skylab and remained on it for twenty-eight days. A second crew remained for sixty days, and a third for eighty-four days. Surveys were taken of Earth's mineral resources and its crops and forests. Photographs of the Sun were also taken.
¡ Saturn: Rich With Moons
1980 AD
SATURN
The probe Voyager 1 passed by Saturn on November 12, 1980. Voyager 2 followed not long after. A number of the satellites of Saturn were for the first time seen as more than points of light.
Titan, the largest satellite, was known to have an atmosphere of methane, but methane turned out to be present in small quantities compared to nitrogen. (Nitrogen is a gas difficult to detect from Earth because its absorption characteristics are not easy to observe and study.) The Titanian atmosphere turned out to be 98 percent nitrogen and 2 percent methane and may be thicker than Earth's atmosphere. The atmospheric haze prevented any view of the surface, where there might be nitrogen lakes with dissolved polymers of methane and (a few speculate) possibly some form of life.
The other Saturnian satellites were, as might be expected, cratered. Mimas, the innermost of the nine sizable satellites, has a crater so large that the impact that produced it must have nearly shattered it.
Enceladus, the second of the nine, is comparatively smooth, while Hyperion is the least spherical and has a diameter that varies from 90 to 120 miles. Iapetus is a two-toned satellite, with one hemisphere much darker than the other, as though one side were icy and the other coated with dark dust. The reason for this is not yet clear.
The Saturn probes succeeded in finding eight satellites that were too small to be seen from Earth, bringing the total number to seventeen. Of the new satellites, five are closer to Saturn than Mimas is. Two satellites that are just inside Mimas's orbit are unusual in being co-orbital. That is, they share the same orbit, chasing each other around Saturn endlessly. This was the first known example of such co-orbital satellites.
The three new satellites beyond Mimas also represent unprecedented situations. The long-known satellite Dione was found to have a tiny co-orbital companion, Dione B, which circles Saturn at a point 60 degrees ahead of Dione. As a result, Saturn, Dione, and Dione B are always at the apices of an equilateral triangle. This is a comparatively stable gravitational position, called a Trojan situation because it is also the position of the Sun, Jupiter, and the Trojan asteroids.
The satellite Tethys has two tiny companions, one 60 degrees ahead of it in orbit and one 60 degrees behind it. Clearly, the Saturnian satellite system is the richest and most complex in the Solar System.
The Saturnian rings were also found to be far more complex than had been thought. From a close view, they consist of hundreds, perhaps even thousands, of thin ringlets, which look like the grooves on a phonograph record. In places, dark streaks show up at right angles to the ringlets, like spokes on a wheel. Then too, a faint outermost ring seems to consist of three intertwined ringlets. None of this can be explained so far. It may be that a straightforward gravitational situation is being complicated by electromagnetic effects.
_Huygens Solves Galileo's Puzzle
1656 AD
THE HAGUE, NETHERLANDS
Galileo had observed Saturn through his telescope in 1612 and noted something odd about it. There seemed to be projections on either side. He could not quite make them out, and after a while they disappeared. It annoyed Galileo. After all, he had been attacked by religionists who said that his telescope produced optical illusions, and here was one case where perhaps it did. He refused to look at Saturn again.
In 1655, however, the Dutch astronomer Christiaan Huygens (1629-1695), with the help of a Dutch philosopher and optician, Benedict Spinoza (1632-1677), worked out a new and better method for grinding lenses. He installed his improved lenses in a telescope that was 23 feet long, and with that he studied Saturn in 1656.
He could see what it was that had puzzled Galileo. Saturn was surrounded by a thin, broad ring that did not touch the planet at any point. No other object in the sky had so peculiar a structure, and Saturn is widely considered the most beautiful object in the sky because of it.
In addition, he discovered that Saturn had a satellite, which he named Titan (because Saturn, or Cronos as the Greeks called him, was the leader of a group of gods called Titans).
That same year, he discovered that the middle star of Orion's sword was not a star but a cloud of luminous gas. It is now known as the Orion nebula.
>The Scales: An Impartial Judge
5000 BC
EGYPT
Trade is bound to lead to measurement -- so much of this for so much of that. You can heft things by hand, but that is subjective and buyer and seller will never agree. The easiest way to be objective is to hang two pans from opposite ends of a rod that is held up in the middle. The thing being weighed is placed in one pan, and standard weights are placed in the other until the two pans are in balance. The principle is so simple and the device itself so easy to make that it may have been used as early as 5000 B.C. in Egypt and have been reasonably accurate.
tPlanes on Water
1911 AD
ALBANY, NEW YORK
The American inventor Glenn Hammond Curtiss (1878-1930) was deeply involved in the early airplane flights. He was the first to fly a mile in the United States, in 1908, and he flew from Albany to New York in 1910.
In 1911 he finally built a practical seaplane, or hydroplane, with pontoons rather than wheels, that could take off and land on water.
âSoutheast Asia: Success, Poverty
1990 AD
SOUTHEAST ASIA
Hot, humid, and covered with jungle. That is the impression many people have of Southeast Asia, but the area is much more than that.
This is one of the fastest growing economic regions in the world. Singapore, Taiwan, Hong Kong, Thailand and other "tigers," as they are sometimes called, have adopted capitalist principles and risen with a dramatic suddenness into the world economic scene.
Not all parts of this region have been so successful. Under the leadership of a socialist-isolationist military government, Myanmar (once called Burma and once the most prosperous country in southeast Asia), is mired in poverty.
1Lightening Women's Work
1846 AD
BOSTON, MASSACHUSETTS
The idea of a sewing machine was natural enough, since machines that wove cloth in patterns had been around for quite a while. The trick was to make the machine small enough and convenient enough to use in the home. There were a number of near misses, but the first that really caught on -- the prototype of those that quickly came to be used -- was invented by the American Elias Howe (1819-1867).
In 1846 he obtained a patent for his device, in which the eye of the needle was placed near the needle point and two threads were used, with stitches made by means of a shuttle. He proved the value of his machine by racing against five women sewing by hand and winning easily.
This was the first product of the Industrial Revolution that specifically lightened a woman's household tasks.
cThe Space Plane
1981 AD
CAPE CANAVERAL, FLORIDA
Until 1981, all space vessels had been one-time operations, not reusable. It was clear that space exploration could be made more feasible if it were made less expensive by creating reusable vessels.
For that reason, the space shuttle was designed. Its purpose was to go into orbit and then return to Earth. It was not in itself designed to make spaceflight cheap; it was an expensive vessel. However, it would help engineers work out the techniques for developing a future generation of such vessels that would be cheaper.
The first shuttle flight took place on April 12, 1981, which happened, by coincidence, to be the twentieth anniversary of the first spaceflight, by Gagarin. The shuttle left and returned safely. It was the first of over a score of such flights during the next four and a half years to be carried through safely.
╧The Milky Way's Spiral Arms
1951 AD
UNIVERSITY OF CHICAGO, IL
The spiral structure of galaxies had first been described in 1845 by Irish astronomer William Parsons, Earl of Rosse (1800-1867), but the structure of our own Milky Way Galaxy remained puzzling. Living within it as we do, we naturally lack the ability to view it from without, from which point of view its structure would become obvious.
By 1951, however, astronomers could detect radio wave emissions with great delicacy, and the American astronomer William Wilson Morgan (b. 1906) could make out the characteristic radio waves of ionized hydrogen coming from particularly hot, bright stars that were themselves characteristic of the spiral arms of galaxies. When several such lines of ionized hydrogen were found coming from our galaxy, it seemed convincing evidence that the Milky Way Galaxy had spiral arms. Our galaxy was thus revealed to be a spiral galaxy much like the Andromeda Galaxy. Our Sun is located in one of these spiral arms.
φSharing Science
1560 AD
NAPLES, ITALY
Throughout history, scientists have usually worked alone because of the difficulty of communication. Sometimes they gathered in some particular center of learning, as in Athens, Alexandria, and Baghdad, but even then their companionship was a haphazard thing.
The coming of printing made it easier to record and publish advances, however, and the affair of Italian mathematicians Niccolo Tartaglia (1499-1557) and Geronimo Cardano (1501-1576) made it important to publish if one wanted credit. There would be value in exchanging information, then, for it would benefit all scientists in their search for reputation.
In 1560 an Italian physicist, Giambattista della Porta (1535?-1615), founded the first scientific association designed particularly for this interchange of ideas, the Academia Secretorum Naturae (Academy of the Mysteries of Nature). It was closed down by the Inquisition, which was oversensitive to any gatherings in those harsh days of religious conflict, but the idea was too good to let go, and other scientific societies were formed in time, and persisted.
These societies helped give rise to a scientific community that was as superior to an individual scientist as a phalanx or legion was to an individual soldier.
uDomes: Impressive, Enlightening
537 AD
CONSTANTINOPLE (ISTANBUL, TURKEY)
A dome is a semispherical structure on top of a building, which looks impressive in itself and gives an opportunity for vertical windows that will introduce light inside. (Skylights on a flat roof are less impressive and are a source of weakness.)
The Romans first introduced domes, placing one on the Pantheon, a building begun in 27 B.C. This was the largest dome built before modern times. It is heavy, however, and is built on a circular building, with no openings except one at the very top, so its esthetic appeal is limited.
About 480 architects in the East Roman Empire perfected a system of placing a hemispherical dome upon a square support in such a way that the bottom of the dome could be pierced by many windows without sacrificing its strength.
This discovery was given its chance when the East Roman Emperor Justinian (who reigned from 527 to 565) decided to rebuild the church of Hagia Sophia after its destruction during a period of rioting. The ruins were cleared, a larger area was marked off, and for six years, ten thousand laborers worked on it. The large dome was so cleverly designed, so skillfully pierced with windows, that the whole interior of the church -- 108 feet across and 180 feet high -- was bathed in sunlight. The enormous dome, as seen from below, seemed to have no support at all but to be suspended from heaven.
_Whew! The Wiggles Won't Hurt
1799 AD
FRANCE
In 1799 French scientist Pierre-Simon de Laplace published the first volume of a monumental five-volume work called Celestial Mechanics, in which the gravitational influences on the various bodies of the Solar System were taken up in detail.
Although the Sun dominates the system, and the planets move about the Sun in stately ellipses, each planet pulls at the others, and so do the satellites. These small additional pulls introduce minor variations in the movement of the planetary bodies, called perturbations, and it was considered that they might gradually increase in size over time so that the Solar System would prove unstable in the long run.
Laplace showed that this was not the case. The perturbations are periodic and vary on either side of what would exist if the Sun alone had a gravitational pull. The Solar System, then, is stable.
╪Electricity From the Sun
1954 AD
UNITED STATES
Eighty years ago, it was discovered that the element selenium could conduct an electric current much more easily in the light than in the dark. It was eventually realized that the energy of sunlight knocked electrons loose from the selenium atoms, and it was those electrons that carried the current.
Selenium came to be used for small jobs. Thus a beam of light shone across a doorway into a selenium receiver and an electric current flowed that kept a door closed against the pull of a spring. If an approaching object interrupted the beam of light, the darkened selenium ceased conducting electricity and the door swung open. The device, popularly known as an electric eye, is more properly called a photoelectric or photovoltaic cell.
Selenium is not suitable for heavy jobs, as it is extremely inefficient, turning less than 1 percent of the energy of sunlight into electricity.
In 1954, however, photovoltaic cells were devised that made use of semiconductors of the type used in transistors. Light kicked electrons out of place much more efficiently in their case; they turned about 4 percent of the sunlight into electricity. At that level, photovoltaic cells could also be referred to as solar batteries.
°Death in Space
1967 AD
CAPE CANAVERAL, FLORIDA
The Space Age, now ten years old, saw its first human casualties. On January 27, 1967, three American astronauts died while an Apollo capsule was being tested on the ground. They were Virgil Ivan (Gus) Grissom (1926-1967), who had orbited in Gemini 3 in 1965; Edward White (1930-1967), who had been the first American to take a spacewalk in 1965, and Roger Bruce Chaffee (1935-1967).
On April 24, 1967, the Soviet spacecraft Soyuz made its first flight, but during the return to Earth, the ship became tangled in its parachute lines and the cosmonaut, Vladimir Mikhaylovich Komarov (1927-1967), who had piloted the first multiperson spacecraft in 1964, died. He was the first person to die in the course of an actual spaceflight.
3Freedom For Divers
1943 AD
FRANCE
Until now, if you wanted to spend a reasonable period of time under water with sufficient mobility to allow exploration, you needed a diving-suit, which was heavy and required a lifeline.
In 1943, even while he was with the French underground fighting the occupying Germans, the French oceanographer Jacques-Yves Cousteau (b. 1910) invented the Aqualung.
This was a device that supplied the diver with air under pressure. It was self-contained and light, so that with an Aqualung and finned devices on their feet, divers could probe under the water's surface with freedom and mobility. This made it possible to observe coral reefs and ocean life in the uppermost layers of the ocean and also introduced a new sport, scuba diving. (Scuba is an acronym for "self-contained underwater breathing apparatus.")
½Walking on Nothing
1965 AD
EARTH ORBIT
In 1965 human beings were able to leave their orbiting rockets and, held by a tether, remain free in space -- within their spacesuits, of course. This was referred to as a spacewalk.
The first to take a spacewalk was the Soviet cosmonaut Aleksei Leonov, who left the rocket ship Voskhod II on March 18, 1965. The American astronaut Edward Higgins White II (1930-1967) left his ship, Gemini 4, on June 3, 1965.
bLight of the Elements
1859 AD
GERMANY
Since their discovery by German physicist Joseph von Fraunhofer (1787-1826) nearly half a century before, spectral lines had not been connected with chemistry.
The German physicist Gustav Robert Kirchhoff (1824-1887), however, had carefully studied the spectra of light produced when various elements were heated to incandescence. He found that each element produced light of only certain wavelengths, so that the spectrum consisted sometimes of only a few lines of light, which were sometimes well separated.
In 1859 Kirchhoff announced that every element produced characteristic spectral lines, which it also absorbed when its vapors were cooler than the light source. The pattern of lines was different for each element; no two elements shared spectral lines in exactly the same positions. In essence, each element had a spectral "fingerprint."
This meant that if any sample of ore, on being heated to incandescence, produced even a single spectral line in a position not recorded for any known element, then some new element must be present in that ore.
Making use of such spectroscopic data, Kirchhoff discovered cesium in 1860. The name is derived from the Latin word for "sky-blue," since that was the color of the spectral line that had given away cesium's existence. The next year Kirchhoff discovered rubidium, a related element, its name coming from the Latin for "red."
Kirchhoff also pointed out that the dark lines in the solar spectrum were the result of light being absorbed by the gases in the relatively cool atmosphere of the Sun. From those lines, one could be sure that sodium existed in the Sun's atmosphere, and half a dozen other elements as well. This was the first actual observation indicating that the same chemical elements that existed on Earth existed also on other astronomical bodies, and therefore presumably throughout the Universe.
▀Fertilization Observed
1875 AD
GERMANY
Egg cells and sperm cells were both known, and it was clear that the birth of young required a union of the two. Nevertheless, such a union was not observed until the German embryologist Oskar Wilhelm August Hertwig (1849-1922) saw a sperm cell actually enter the egg cell of a sea urchin.
What's more, although sperm cells are produced in swarming plenty, Hertwig could see that but a single sperm cell entered the egg cell and that it sufficed for fertilization.
PThey Aren't All Worms
1801 AD
FRANCE
Swedish scientist Carolus Linnaeus (1707-1778) and others in the past three-quarters of a century had elaborated the taxonomy of vertebrates (those animals with backbones -- mammals, birds, reptiles, amphibia, and fish) in considerable detail.
The less familiar and more diverse animals without backbones (invertebrates) were less carefully considered. Linnaeus had lumped them all into the class Vermes (Latin for "worms").
The French naturalist Jean-Baptiste de Lamarck (1744-1829) tackled the problem in publications beginning in 1801. He divided the invertebrates into groups and created such divisions as the crustaceans (crabs and lobsters) and echinoderms (starfish and sea urchins). He distinguished between the eight- legged arachnids (spiders and scorpions) and the six-legged insects. In fact, Lamarck was the first to use the terms vertebrate and invertebrate, and he popularized the term biology for the study of life.
In founding the modern science of invertebrate zoology, Lamarck began the process of understanding the importance of invertebrate life. All the vertebrates are included in but a single phylum, while there are about twenty-two phyla of invertebrates. The number of species of insects alone far exceeds the number of species of vertebrates; indeed, it exceeds the number of species of all other animals combined.
çSputnik Sends U.S. Into Orbit
1957 AD
EARTH ORBIT
Nearly three centuries before, Newton had pointed out how a rocket could put a vehicle into orbit around the Earth. After Germany had developed the V-2 rocket during World War II, both the United States and the Soviet Union began to think of placing a rocket in orbit. It was naturally taken for granted by all Americans that the United States, with its advanced technology, would be first in the field.
It came as an enormous shock to the United States then, when on October 4, 1957, the first satellite went into orbit -- and was Soviet. It was called Sputnik I (the Russian word for "satellite"), and it began the Space Age.
ÄPasteur Blames Germs
1862 AD
PARIS, FRANCE
More and more biologists were coming to suspect that contagious diseases were caused by microorganisms.
In 1862 Pasteur took up the matter and issued a publication that gathered all the evidence. His prestige was such that the germ theory of disease then had to be taken seriously. There is no question but that this was the most important single advance in the history of medicine.
Using the theory, Pasteur, and others as well, located the specific microorganisms that caused certain diseases and could then work out logical ways of preventing the disease in the first place or of curing it once it struck.
This was the beginning of modern medicine. It led to a fall in the death rate, a doubling in life expectancy, and an accelerated population explosion that has more than tripled world population since Pasteur's time and presented humanity with enormous problems in consequence.
∙Guericke's Spark Maker
1660 AD
MAGDEBURG, GERMANY
When Greek philosopher Thales (624-546 B.C.) studied the magnetic properties of loadstone, he is also supposed to have studied amber, which, when rubbed, attracts light objects. Whereas magnets attract only iron, rubbed amber attracts many things.
English physicist William Gilbert (1544-1603), who showed that Earth was a magnet, found that rock crystal and a variety of gems showed the same attractive force when rubbed that amber did. Since the Greek word for amber was elektron, Gilbert called these substances electrics, and the phenomenon came to be called electricity. Because the electricity in electrics seemed to stay put if left undisturbed, it was referred to eventually as static electricity, from a Greek word meaning "to stand."
The first to demonstrate static electricity on a large scale was German physicist Otto von Guericke (1602-1686), who had invented the air pump. The electrical phenomenon was produced by rubbing, and Guericke in 1660 fashioned a globe of sulfur that could be rotated on a crank-turned shaft. When it was stroked with the hand as it rotated, it accumulated quite a lot of static electricity. It could be discharged and recharged indefinitely, and Guericke could produce sparks from his electrified globe.
fGoodbye Paddlewheel!
1827 AD
UNITED KINGDOM
Steamships were propelled by large paddlewheels on one side during the quarter- century of their existence. They worked well enough ordinarily, but in rough seas they could lift out of the water altogether if the ship listed to the other side, and that complicated steering. Furthermore, they were vulnerable to enemy fires so that it was considered completely impractical to power warships by steam.
In 1827, however, a British engineer, Robert Wilson (1803-1882), designed a screw propeller, which worked from the stern of the ship, so that it was symmetrically placed and was little affected by the ship's rolling. It was also well under water and so less vulnerable than the rest of the ship. Since it was judged to be a more efficient propulsion mechanism than the paddlewheel, it became possible to think of steam-powered warships thereafter.
Skipping Steps to Steel
1856 AD
LONDON, ENGLAND
For over three thousand years, steel had been known to be the strongest metal, but manufacturing steel was a difficult process. First, iron came out of the smelting furnace with a great deal of carbon in it (from the charcoal or coke used to smelt it). This cast iron was hard but brittle. The carbon could be removed and pure iron (wrought iron) left behind. This was tough but too soft. Then finally, just the right amount of carbon could be added to form steel, which was both tough and hard. By then, steel was expensive.
The British metallurgist Henry Bessemer (1813-1898) sought a way of removing the carbon from cast iron more cheaply. In the old way, the carbon was burned off by oxygen from additional iron ore while the mixture was strongly heated. Bessemer wondered if the oxygen could not be supplied more simply by sending a blast of air through the molten iron. It might seem that the blast would cool the iron and spoil everything, but the combination of oxygen from the air and carbon in the iron actually heated the mix. By stopping the process at the point where the carbon level was right, Bessemer got his steel directly.
In 1856 Bessemer announced his discovery, and such blast furnaces began to be built. It took a while for the method to be perfected because it required phosphorus-free iron ore, something the steel manufacturers didn't understand. Eventually, however, the bugs were worked out and the era of cheap steel began. Steel, together with elevators, helped build the cities of the next century.
s
Calculating the Years
2800 BC
EGYPT and ENGLAND
Use of the day (or the alternation of day and night) and parts of the day as determined by a sundial is insufficient as a means for keeping track of time. Certain phenomena, such as the changing of the seasons, have periods that are several hundred days long. It is tedious to count those days, and the chances of mistakes are great.
There is a cycle of intermediate length, however, that of the phases of the Moon. It takes 29 or 30 days for the Moon to go through its cycle of phases, and it takes 12 or 13 of these cycles (months, from the word Moon) to make up the cycle of the seasons.
We don't know when people first began to attach importance to the months.
There are indications that even prehistoric people counted them, but it was the people of the Tigris-Euphrates region who first systematized the matter. They worked out a cycle of 19 years, in which certain years had 12 lunar months and others had 13 lunar months. Such a cycle kept the years even with the seasons.
This lunar calendar was adopted by the Greeks and the Jews and is still used as the Jewish liturgical calendar.
The Egyptians, however, did not make use of the Moon primarily. To them, the important feature of the year was the periodic flooding of the Nile. The priests in charge of irrigation carefully studied the height of the river from day to day and eventually discovered that, on the average, the flood came every 365 days. That was also the time it took the Sun to make an apparent circuit of the sky relative to the stars. (In modern times, we view this as the time it takes the Earth to go around the Sun.) This is the solar year, and a calendar based on it is a solar calendar.
The Egyptians were aware that there were 12 new Moons to the year, so they had 12 months, but they made each month 30 days long, paying no attention to the actual phase of the Moon. That made 360 days, to which they added 5 more days at the end.
This calendar was much simpler and handier than any other calendar invented in ancient times. Historians are uncertain of the date when it was first adopted, but priests may have been using it for their private computations (it obviously made them more powerful if they alone knew when the Nile would flood) as early as 2800 B.C.
Nothing better than the Egyptian calendar was devised for nearly three thousand years, and even then what was produced was a mere modification of it -- and not all the changes were for the better. Our present calendar is still based on the Egyptian calendar, with changes that are, in some cases, also not for the better. This makes our calendar, in essence, nearly five thousand years old.
ûTools: Not Just for People
2,000,000 BC
EAST AFRICA
Sometimes, we think of the human being as a tool-using animal. Tool-using is not really unique to human beings, however. For example, sea otters routinely smash shellfish against a rock they carry for the purpose on their abdomens as they float belly-up. A long litany of other examples could also be given.
If we change that to tool-making animal, we are somewhat better off, but not entirely. Chimpanzees have been seen to strip leaves from twigs and then use the bare twigs as devices for capturing termites, which to them are tasty snacks.
Undoubtedly, australopithecines could do anything that chimpanzees could do. We have no evidence, but we can be fairly certain that they used tree branches and long bones as clubs. They could surely throw rocks or use them as sea otters do.
The australopithecines may have existed on Earth for three million years, not becoming finally extinct till as late as 1,000,000 B.C. For the final third of their existence, though, they were no longer the only hominids.
About two million years ago genus Homo came into existence. For a time, it coexisted with the australopithecines, but there was bound to be conflict between them, and in this, the larger and brainier hominids won out, contributing (very largely, perhaps) to the extinction of the australopithecines.
In the 1960s, the English anthropologist Louis Seymour Bazett Leakey (1903-1972), his wife, Mary, and their son, Jonathan, located remains of the oldest of the genus Homo in the Olduvai Gorge, in what is now Tanzania. The hominids thus uncovered were named Homo habilis (Latin for "able man," because with them were discovered objects that seemed to indicate that they made simple stone tools).
Homo habilis was smaller than some of the larger species of australopithecines. When, in the summer of 1986, fossil remains of Homo habilis were discovered that were some 1.8 million years old (the first time that both skull fragments and limb bones of the same individual of that species had been located), they seemed to represent a small, light adult about 3-1/2 feet tall and with arms that were surprisingly long.
Though members of Homo habilis may have been small, they had more rounded heads than any of the australopithecines and larger brains, nearly half as large as those of modern human beings. They had thinner skull bones, and based on the brain configuration, if they could not talk, they could at least make a greater variety of sounds. Their hands were more like our modern hands, and their feet were completely modern. Their jaws were less massive, so that their faces looked less apelike.
These creatures apparently used stone tools to chip pieces of flint and so create a sharp edge. This meant that for the first time, hominids had sharp edges in quantity and did not have to depend on the chance finding of one. Moreover the edges could be made truly sharp, and the sharpness could be renewed when the rock was blunted.
These stone knives increased the food supply. Homo habilis could not tear away at the tough hides of animals, as fanged predators such as the various cats, dogs, and bears could. Without knives, hominids had to make do with carcasses that had already been mangled by other predators and to make off with what they could scavenge.
With knives, however, Homo habilis had artificial fangs that could slit hides and scrape the meat off hides and bones. What's more, Homo habilis no longer had to scavenge. Hominids could now kill animals on their own, even fairly large animals. And once they caught on to the trick of tying stone axes to wooden branches and creating the first crude spears, they could stab animals at a distance. If the spears were thrown, the distance could be made long enough to obviate immediate retaliation.
Hominids became hunters and killed off the competing australopithecines, no doubt, so that for the last million years, all hominids, without exception, have been part of genus Homo.
ÆThe Hero Fungus
1940 AD
WOODS HOLE, MASSACHUSETTS
American microbiologist Rene Jules Dubos's (1901-1982) discovery of tyrothricin had galvanized one of his past teachers, the Russian-born American microbiologist Selman Abraham Waksman (1888-1973).
Using Dubos's methods, Waksman began to search for bacteriocidal compounds in microscopic fungi. In 1940 he located one he called actinomycin because it was found in fungi of the Actinomycetes family. Not long after, he found one in fungi of the Streptomycetes family and called it streptomycin.
Streptomycin was quite effective against bacteria that were not affected by penicillin but was considerably more toxic to human beings than penicillin and had to be used very cautiously.
It was Waksman who coined the term antibiotic (from Greek words meaning "against [microscopic] life"), and for his work on them, he was awarded the Nobel Prize for medicine and physiology in 1952.
1Yup! The Sun Moves Too
1783 AD
BATH, ENGLAND
To the ancients, the Earth was the motionless center of the Universe. To the early moderns, the Sun was.
In 1783, however, British astronomer William Herschel (1738-1822) began a systematic measurement of the proper motion of a great many stars. Very dim and very distant stars moved so slightly they could be considered motionless and were references against which the perceptible motions of the nearer stars could be measured.
As the years passed, Herschel found that in one direction in the sky, the stars were generally moving away from each other, while in the opposite direction they were very slowly closing in toward each other. In 1805 he came to the conclusion that this could best be explained by supposing that the Sun itself was moving toward that point from which stars seemed to be separating and was moving away from the point toward which other stars seemed to be converging. Just as Polish astronomer Nicolaus Copernicus (1473-1543) had maintained that the Earth was a planet like other planets, moving as they did, so Herschel now maintained that the Sun was a star like other stars and was moving as they did.
But if neither the Earth nor the Sun was the motionless center of the Universe, what was? There was no other candidate, and the question had to remain in abeyance for a time.
^Why the Sun Shines
1853 AD
GERMANY
It had been assumed for thousands of years that the Sun was eternal and changeless (and would be until God wished to put it to an end). The discovery of sunspots had shaken this belief but not destroyed it.
Once the law of conservation of energy was well established, however, the shining of the Sun had to be questioned. Light and heat were energy, and this could not be created out of nothing. Where, then, did the Sun obtain the energy that had kept it shining brilliantly enough to warm the Earth at a distance of nearly a hundred million miles for all the many thousands of years of history? It could not be ordinary burning, for the entire substance of the Sun would have been consumed in a mere fifteen hundred years in that case.
Helmholtz, who had been the one to establish the law of energy conservation, pondered the matter and by 1853 had decided that the only energy supply that would suffice was that of the Sun's own gravitation.
Slowly, the Sun's globe must be contracting, and the falling inward of that huge mass must be supplying the energy that was converted into light and heat. This must be the continuation of a process that had begun when a gigantic cloud of dust and gas had contracted to form the Sun in the first place.
In order to supply light and heat at the current rate, Helmholtz concluded, the Sun must have contracted from a size filling the orbit of the Earth to its present size in something like twenty-five million years. That meant Earth could be no older than that. Moreover, it meant that in another ten million years, the Sun would be too small and cool to support life on Earth.
This conclusion came as a great shock to geologists, who already thought the Earth must be considerably older than twenty-five million years. It was to be another half-century before the controversy was settled -- in favor of the geologists.
°Fast Money Losers
1970 AD
ENGLAND AND FRANCE
Once the sound barrier had been broken it became possible to build commercial jet planes that would routinely carry passengers at speeds greater than sound.
In 1970 such supersonic transport (usually abbreviated SST) came into use. The United States decided not to build them for reasons of noise and environmental damage, but Great Britain, France, and the Soviet Union did build them. Although they have worked well technologically, they have never proved a commercial success.
Zero Resistance
1911 AD
NETHERLANDS
Dutch physicist Heike Kamerlingh Onnes, having in 1908 liquefied helium and obtained temperatures of 4 degrees above absolute zero (4° K) and even lower, was eager to study the properties of matter at such exceedingly low temperatures.
For instance, it was known that metals tended to lessen their resistance to an electric current as the temperature went down. It seemed to Kamerlingh Onnes that this lessening must continue all the way down to absolute zero, where it must disappear altogether.
He tested the matter on mercury, and resistance dropped more or less as expected till he reached a temperature of 4.2° K. There, to his surprise, the resistance dropped suddenly to zero.
This phenomenon -- the perfect conductivity of an electric current at temperatures close to absolute zero -- was called superconductivity.
It was soon found that other metals (though not all) also showed the phenomenon, the resistance dropping to zero at some very low temperature that was characteristic for each metal.
╙Bang Replaces Twang
1289 AD
LONDON, ENGLAND
Roger Bacon wrote of gunpowder in 1249, but there is no question about its place of origin: China had it first by many centuries, and the Mongols may just possibly have brought it west with them.
There are Chinese books that still survive, dating back to 1044, that give the proportions of saltpeter, charcoal, and sulfur for the making of gunpowder.
The Chinese exploded the gunpowder in bamboo tubes and rockets and used it against the Mongols. These were not powerful weapons. They may have served only to frighten horses and in any case did not stop the Mongols.
As in the case of the magnetic compass, the Europeans, once they learned of gunpowder, moved quickly to make it a serious weapon.
²Goldmark's Color TV
1940 AD
NEW YORK, NEW YORK
Although television existed as a laboratory exercise only and wouldn't enter the American home till after World War II, methods were already being developed to transmit television in full color.
The first to work out such a system was the Hungarian-born American engineer Peter Carl Goldmark (1906-1977), who used a rotating three-color disk for the purpose in 1940. The method was not, in the end, used. More effective methods were finally made commercial some fourteen years later.
╖Back and Forth Electricity
1883 AD
NEW YORK, NEW YORK
Electric currents, as used in the first half of the nineteenth century, flowed from one point to another in one direction. That is the kind of current one gets from batteries, and it is direct current (dc). It is easier, in working with electric generators, however, to get a kind of current that goes first in one direction, then in the other, alternating very rapidly, with the current intensity rising and falling like a sine wave. This is alternating current (ac).
Alternating current didn't seem as useful as direct current, but then in 1883 a Croatian electrical engineer, Nikola Tesla (1856-1943), constructed an induction motor that could make use of alternating current to do useful work. Edison had committed himself to direct current, and he fought the use of alternating current, but he lost out eventually.
Tesla made alternating current useful, and by 1893 a German-born American electrical engineer, Charles Proteus Steinmetz (1865-1923), worked out the intricacies of alternating current circuitry in complete mathematical detail, making use of complex numbers.
This made it possible to design alternating current equipment with increased efficiency. Steinmetz's mathematics spread among the electrical engineering profession and completed the victory of alternating current over direct current. (The house current we draw on whenever we plug an electrical device into a wall socket is invariably alternating current.)
;Measuring Temperature
1592 AD
ITALY
The concept of hot and cold must be as old as humanity. We can all tell when an object is hot or cold by placing the hand near it (not even necessarily on it). We can also tell if one subject is substantially warmer than another. Such subjective sensations are useless, however, where small differences in temperature are concerned and are, in any case, untrustworthy. A humid day feels hotter than a dry day at the same temperature; a windy day colder than a calm day at the same temperature.
What is needed is some physical phenomenon that changes regularly in a measurable way with changes in temperature, and the first person to attempt to find such a phenomenon was Galileo Galilei (1564-1642).
He warmed an empty bulb with a long tube extending from it, then placed the open end of the long tube into a container of water. As the warm air within the bulb cooled, it contracted, and water was drawn up into the tube. As temperature changed and the air within the bulb cooled or warmed, the water level rose or fell accordingly, and from the position of the level, one could judge the temperature.
This was a very crude device, because for one thing the water level was also affected by the air pressure upon the water reservoir. Nevertheless, it was the first thermometer (from Greek words meaning "to measure heat").
t Harnessing Hydrogen
1951 AD
PRINCETON, NEW JERSEY
Nuclear fission was clearly not the ultimate nuclear energy source. It was well known that nuclear fusion, as in the conversion of hydrogen to helium taking place in the stars, would yield up to seven times as much energy, weight for weight, as nuclear fission.
Moreover, the ultimate fusion fuel, hydrogen, is available in virtually unlimited quantities on Earth and is easily obtained, as compared with the rarer and far more difficult to extract uranium and thorium needed as fission fuel. Still further, fusion produces less dangerous products than fission does. However, whereas nuclear fission can be initiated at room temperature, through the use of slow neutrons, nuclear fusion requires the high temperatures and pressures found at the center of stars.
Uncontrolled fusion is comparatively simple. Some way can be found to include hydrogen and other light elements with an ordinary fission bomb in such a way that the fission explosion produces sufficient temperature and pressure to ignite the much more powerful and destructive fusion explosion. The result would be a nuclear fusion bomb, more popularly known as a hydrogen bomb, or an H-bomb. It can also be called a thermonuclear device, where thermo- means "heat," because that's what is needed.
The fact that the Soviet Union had developed its own fission bomb made some scientists, notably the anti-Soviet physicist Edward Teller (b. 1908), feel that the United States should immediately develop a hydrogen bomb in order to maintain its preponderance of power. Other scientists, notably Robert Oppenheimer (1904-1967), sickened at the thought of the damage such bombs could do and aware that the Soviets would then simply match it, were opposed. The political decision was to go ahead with the H-bomb, and Teller saw to it that Oppenheimer's opposition was used to put an end to his career.
Meanwhile, an attempt began to devise a way to produce controlled hydrogen fusion as a source of peaceful energy -- a much harder task. It would be necessary to raise the temperature of hydrogen to tens or even hundreds of millions of degrees, while confining this ultrahot hydrogen long enough to allow fusion to begin.
At this temperature, however, hydrogen's tendency is to expand explosively and be gone unless it is tightly enclosed. No material container would do, for either the hot hydrogen would melt the container or the cold container would cool off the hydrogen.
The hydrogen might be confined by a magnetic field, however. It would then merely be necessary to devise some way of shaping a magnetic field that was strong enough to do the job.
In 1951 the American physicist Lyman Spitzer, Jr. (b. 1914) supervised the construction of a figure-8 device called a stellarator (from the Latin word for "star," because it was trying to duplicate what went on in stars) that might confine hot hydrogen gas efficiently. Later, a modified version developed in the Soviet Union and called a Tokamak (an abbreviation of a descriptive Russian phrase) was used.
In nearly forty years of trying, however, nuclear fusion ignition has not been achieved, though progress continues to be made.
▌All It Needs Is Tracks
1804 AD
ILLOGAN, CORNWALL, ENGLAND
If steam can turn paddle wheels in the water, it can also turn wheels on land, so that one can imagine a steam locomotive (from Latin words meaning "moving from place to place"). To be sure, such a steam-powered land vehicle would lose too much energy crossing over rough ground. A smooth road would have to be built.
It occurred to a British inventor, Richard Trevithick (1771-1833), that what was needed was iron rails on which the wheels would fit and along which they could move, a railroad. He showed that, even if the rails were smooth and the wheels rolling on them were smooth as well, there was still sufficient traction for the locomotive to move itself and a train of coaches attached. Trevithick showed this by actual demonstration as early as 1801. In 1804, one of his locomotives pulled five loaded coaches for 9.5 miles at nearly 5 miles an hour.
Nevertheless, Trevithick could not manage to turn his locomotive into a commercial success.
┤The Wooden Calendar
1920 AD
PETRIFIED FOREST, ARIZONA
Ancient wood is well preserved in Arizona's dry climate, and the American astronomer Andrew Ellicott Douglass (1867-1962) grew interested in it.
The wooden trunk of a tree contains rings that mark annual growth, wide ones in good years, narrow ones in bad years. Since all trees in a region share the same good years and bad years, all of them have similar tree-ring patterns.
These patterns are characteristic and do not ever quite repeat themselves over time. Therefore, if a piece of old wood is placed overlapping the tree-ring pattern of a freshly produced tree stump, you can determine the year in which the old wood was cut by counting rings of the new wood back to where the overlap begins. You can then follow its pattern back farther than you could that of the fresh wood, still older pieces of wood can be fitted on, and so on.
By 1920, when Douglass convinced himself that such dendrochronology (Greek for "time-telling by trees") was a practical way of determining age where wood was concerned, he had traced his tree-ring calendar back for about five thousand years. The technique was particularly useful in dating objects of Native American prehistory.
╞Transistors: I Hear You
1953 AD
DALLAS, TEXAS
The transistor had been invented by American physicist William Bradford Shockley (b. 1910) and his group in 1948, but its performance was at first unreliable. However, reliability improved rapidly, and by 1953 the first significant transistorized instruments for use by the general public were introduced. These were hearing aids that were so small they could fit into the ear opening. They replaced, and worked better than, previous devices, which were heavy, bulky, and embarrassingly noticeable.
Meanwhile, Japan was working to produce transistorized radios, which would be much smaller than any till then in use and more reliable. The world was about to enter an age of miniaturization.
BFeatherless Bipeds
4,000,000 BC
EAST AFRICA
The first human advance was biological. It consisted of becoming human.
We might ask what makes a human being human. What part is sufficiently human so that we can at once point to it and say, "This is human. Without it, this organism would be something else."
As we go back in time, studying the bones and teeth (all that remain) of earlier forms of hominid life, we come to an organism that was perhaps the size of a modern chimpanzee or even a little smaller and with a brain that was no larger. Yet in one crucial respect, it was much closer to the human than to the ape. This human characteristic is so obvious that, if we were to see the organism in real life, we would at once say, "This is no ape."
It was the first hominid, and what made it so was its bipedality. It walked on two legs, as we can tell from the shape of its spinal column, its pelvic girdle, and its thighbones.
The fact that human beings walk on two legs strikes us as characteristically human. We are bipeds (from Latin words for "two legs"), while other mammals are quadrupeds (four legs).
Of course birds walk, run, or hop on two legs, and the Greek philosopher Plato (ca. 427-ca. 347 B.C.) therefore defined a human being as a "featherless biped." That is insufficient, however, for there are bipeds with fur (kangaroos and jerboas) and bipeds with scales (various dinosaurs), which Plato knew nothing about.
The earliest hominids were first identified by an Australian-born South African anthropologist, Raymond Arthur Dart (1893-1988), to whom a skull, rather human-looking except for its extraordinarily small size, was brought from a South African limestone quarry in 1924. Dart, in 1925, named the type of organism to which the skull belonged Australopithecus (from Greek words meaning "southern ape"). Further finds made it clear that it was not an ape but a hominid, and at least four different species have now been identified, which are lumped together as australopithecines.
In 1974 an American anthropologist, Donald Johanson, unearthed an unprecedentedly complete and ancient skeleton of an australopithecine female, who was given the name Lucy. (You can tell a female from a male by the shape of its pelvis.) It was possibly as much as four million years old judging from the age of the rocks in which it was found.
Lucy is an example of Australopithecus afarensis, because Afars is the name of the region in east-central Africa where her remains were found. Australopithecines existed only in eastern and southern Africa, so east-central Africa may have been the cradle of humanity.
Lucy was the size of a chimpanzee and slighter in build. Her australopithecine relatives seem to have ranged between 3 and 4 feet in height and to have weighed perhaps 65 pounds. Their brains were no larger than a chimpanzee's and about a quarter the size of our own.
The early australopithecines probably lived much as chimpanzees do, may have spent their time partly in trees, must have been very largely vegetarian, and undoubtedly could not speak. However, they were as bipedal as we are and walked as easily and as comfortably on their hind legs as we do.
Why did the australopithecines develop the backward bend in the spine?
Some arboreal prehominids managed to adapt to the grasslands in east-central Africa and to spend more and more time out of the trees. It must have been a difficult transition. As they spent more time on the ground, they had an increasing tendency to rise to their hind legs and peer about over the tall grass, searching for food or watching out for predators. Those who could stand upright more easily and could do so for longer intervals were better able to survive.
Even a slight crook in the spine, which made standing upright slightly easier, gave those who had it a better chance of surviving, and of having children to inherit that crook. What we call natural selection would thus drive the prehominids toward bipedality and a true hominid character.
Any change that made the brain a bit larger or more complex made it possible for the brain to handle the flood of sensation more efficiently, and this led to an improved chance of survival. Thus, natural selection introduced a drive for bigger and better brains.
The early australopithecines, with a brain as large as that of a chimpanzee but with a body that was slighter, already had a larger brain-to-body ratio than any pongid then or since. Since the brain-to-body ratio is a crucial factor in what we call intelligence (provided the brain is reasonably large), the australopithecines were probably the most intelligent land animals existing in their time.
"Tycho's Supernova
1572 AD
DENMARK
A supernova, like the one that had appeared in 1054, blazed out in the constellation of Cassiopeia, high in the northern sky, in November 1572. The supernova of 1054 had gone unobserved in Europe, but times had changed.
A young Danish astronomer, Tycho Brahe (1546-1601), usually known by his first name, watched the new star carefully from night to night. When he first saw it, it was brighter than Venus, but it gradually faded until in March 1574, it could no longer be seen at all. Tycho had watched it for 485 days.
The Greeks had assumed that the heavens (unlike Earth) were perfect and unchanging. Anything in the sky that seemed to change (or to move in anything but a regular and predictable path) could not be part of the sky, they thought, but must be part of the atmosphere of the imperfect Earth. This included clouds, shooting stars, and comets.
The new star, being a temporary phenomenon, ought to be part of the atmosphere, too, but although Tycho tried to determine its parallax, he could detect none. The new star must be beyond the Moon and therefore be part of the heavens, possibly a very distant part. The notion of heavenly perfection and immutability was destroyed.
In 1573 Tycho published a small book detailing all his observations of the star, with a title usually given in short form as De Nova Stella (Concerning the New Star). Because of that title, stars that suddenly appear in the sky are now known as novae (the Latin plural) or novas (the English plural).
Tycho was suddenly the most famous astronomer in Europe.
╝No, Not a Rhinoceros
1822 AD
LEWIS, SUSSEX, UNITED KINGDOM
In 1822 an English geologist, Gideon Algernon Mantell (1790-1852), uncovered the bones and teeth of a large animal and sent some of them to French anatomist Georges Cuvier (1769-1832). For once Cuvier made a mistake and thought the teeth were those of a rhinoceros-like mammal.
A couple of years later, Mantell came across the teeth of an iguana, a reptile that lives in desert areas of North America. The fossil teeth he had found were precisely like those of the iguana but much larger. Mantell realized then that he had uncovered an ancient reptile and named it iguanodon (from the Greek meaning "iguana-tooth").
As it turned out, he was the first to discover an example of what were eventually to be called dinosaurs (from Greek words meaning "terrifying lizards"). Dinosaurs proved to be by far the most dramatic relics of past ages and did more to acquaint the ordinary person with evolution than anything else.
ªThe Universal Computer
1951 AD
PHILADELPHIA, PENNSYLVANIA
American engineers John William Mauchly (1907-1980) and John Presper Eckert, Jr. (b.1919) who had designed ENIAC in 1946, designed UNIVAC (Universal Automatic Computer) in 1951. It was the first computer to make use of magnetic tape and the first to be mass-produced rather than individually built by the designers for their own use. It marked the beginning, then, of computers in industry.
ßThe Other Ringed Planet
1781 AD
BATH, ENGLAND
Since prehistoric times, human beings had been aware of the five bright starlike planets: Mercury, Venus, Mars, Jupiter, and Saturn. With the coming of Copernican principles in 1543, Earth itself became a sixth, coming between Venus and Mars. It seemed somehow impossible that there could be another. Surely, if there were another, it would have been seen.
In the 1770s, a British astronomer (of Hanoverian birth) began studying the heavens. He was William Herschel (1738-1822). A music teacher by profession, he had grown interested in astronomy. Unable to buy a telescope he considered sufficiently good, he took to grinding his own lenses and mirrors and ended with the best telescopes of his time.
He determined to study, systematically, everything in the sky, and on March 31, 1781, he came across an object that appeared as a disc instead of as a mere point of light. He supposed it to be a comet, but the disc had sharp edges like a planet and wasn't fuzzy as a comet would be. Furthermore, when enough observations had been made to calculate an orbit, he found that orbit to be nearly circular, like a planet's, and not elongated, like a comet's. What's more, it was clear that the object's orbit lay far outside that of Saturn. It was twice as far from the Sun as Saturn was, and no comet could be seen from that distance.
The conclusion was that Herschel had discovered a seventh planet circling the Sun, which because of its great distance did not appear as bright as the others. In fact, it was visible to the unaided eye as a very dim star and had been observed a number of times by people who never suspected it might be a planet. The first had been English astronomer John Flamsteed, who had recorded its position on his star map a century earlier and called it 34 Tauri.
After some hesitation, astronomers decided to continue naming planets for mythological characters, and the new planet was named Uranus, after the father of Saturn (Cronos) in the Greek myths.
The discovery of Uranus doubled the size of the Solar System at a stroke. It was further spectacular proof that the ancients had not known everything, and gave astronomers the exciting knowledge that there was more to be discovered in the sky than additional comets.
éNorth America: Vast and Varied
1990 AD
NORTH AMERICA
Few continents of the world have as much variety as North America.
Included in the vast expanse of Canada and the United States are the wide rolling plains of the Midwest; the rugged Rocky Mountains; one of the world's great rivers, the Mississippi; the Great Lakes, some of the largest fresh-water lakes in the world; primitive forests; jungles; swamps and frozen tundra.
North America was first settled by tribal peoples who are believed to have entered the continent across the Bering Strait, that point where Alaska and Asia almost come together.
Later, following the voyages of Christopher Columbus in 1492, the continent was settled by various European groups.
The United States secured its independence from Great Britain following the American Revolution (1776-1781) and began expanding to the west across the continent, purchasing vast tracts of land from France (the Louisiana Purchase) and Russia (Alaska) and taking much of what is now the Western United States from Mexico in what many feel was an unjust war.
Since then, the United States has grown into one of the world's greatest economic and military powers.
eBlack Hole X-Rays
1971 AD
CANADA
In 1971 an X-ray-detecting satellite found irregular changes in an X-ray source in the constellation of Cygnus, a source that had been named Cygnus X- 1. Such irregular changes might be the result of matter circling a black hole in varying concentrations.
Cygnus X-1 was at once investigated with great care and found to exist in the immediate neighborhood of a large, hot, blue star about thirty times as massive as our Sun. The Canadian astronomer C. T. Bolt showed that this star and Cygnus X-1 were revolving about each other, and from the nature of the orbit, Cygnus X-1 had to be five to eight times as massive as our Sun. If Cygnus X-1 were a normal star, it would be easily visible. Since it was not, it must be a small, very dense object. It was too massive to be a neutron star, so it must be a black hole. Though this is not a clear-cut and absolute identification, astronomers are by and large satisfied that it is a black hole.
Since then, black holes have been observed, by similar indirect and not entirely reliable means, to exist in the centers of various galaxies, including perhaps our own.
Why Venus is Fuzzy
1761 AD
ST. PETERSBURG, RUSSIA
Unlike the other planets, Venus had no markings. It always presented a featureless white orb. It remained interesting, however, because periodically (being closer to the Sun than Earth is) it passed exactly between Earth and Sun. On such occasions, it appeared as a small black sphere moving across the face of the Sun. This is called a transit of Venus.
In 1761 there was a transit of Venus coming and astronomers organized expeditions to Newfoundland and to St. Helena to observe it from widely separated spots. If the exact time at which Venus's orb first touched the Sun's rim and the exact time at which it finally left on the other side were determined from those widely separated spots, Venus's parallax could be determined, and its distance, together with that of the Sun, might be determined to a higher degree of accuracy than was produced by Cassini's determination of the parallax of Mars.
The expedition failed. The time when Venus entered and left the solar sphere could not be determined accurately, to the frustration of all.
One observer, the Russian scientist Mikhail Vasilievich Lomonosov (1711-1765), pointed out that this could be due to Venus's possession of an atmosphere. The atmosphere would fuzz Venus's outline, so to speak, and make the points of contact difficult to time. Furthermore, if the atmosphere had a permanent cloud layer, that would help explain both Venus's brilliance (since the cloud layer would reflect most of the sunlight striking it) and its featurelessness.
=Mapping Venus
1978 AD
CAPE CANAVERAL, FLORIDA
The United States launched Pioneer Venus on May 20, 1978, and it went into orbit about Venus on December 4, 1978. It sent several probes into Venus's atmosphere and found that the cloud layer contained droplets of sulfuric acid, that about 2.5 percent of the sunlight striking the cloud layer penetrated to the surface of the planet, and that the atmosphere was 96.6 percent carbon dioxide and 3.2 percent nitrogen. In view of its density, that meant Venus's atmosphere had more than three times as much nitrogen as Earth's.
Venus Pioneer also beamed radar waves at Venus, and from the reflections, details of the surface (otherwise invisible from outside the cloud layer) could be determined.
The surface of Venus does not appear to be broken into plates as Earth's is and is mostly of the type we associate with continents. It seems to have a huge supercontinent that covers about five-sixths of the total surface, with the remaining sixth a lowland that may once have contained water.
In the north is a large plateau named Ishtar Terra, about as large as the United States. On the eastern portion of the plateau is a mountain range. There is another and even larger plateau in the equatorial region called Aphrodite Terra. It too has mountains.
There are also canyons and what may be extinct volcanoes.
_Change From Underground
1765 AD
FRANCE
The French geologist Nicolas Desmarest was interested in the changes taking place on the face of the Earth. He was the first to maintain that valleys had been formed by the streams that ran through them.
In 1765 he carried forward the ideas of French geologist Jean-Étienne Guettard (1715-1786). Not only did he maintain that heat was the source of change, but he saw it as having been applied through volcanic action. He maintained that basalt was a rock of volcanic origin and that large sections of France's rocks consisted of ancient lava flows. He was a Plutonist, in other words (from the Greek god Pluto who was lord of the underworld). However, most geologists remained under the spell of a German geologist, Abraham Gottlob Werner (1750-1817), who was a Neptunist and insisted that water was the source of all change in the Earth's surface.
░Flowing Electricity
1800 AD
COMO, ITALY
In 1780, Italian anatomist Luigi Galvani (1737-1798), noting that dead muscle twitched when touched simultaneously by two different metals, had decided that electricity was involved and that it originated in the muscle. The Italian physicist Alessandro Giuseppe Volta (1745-1827) thought the electricity originated in the metals.
He began to experiment with different metals in contact and was soon convinced that he was correct. In 1800 Volta constructed devices that would produce electricity continuously if it was drawn off as produced. This created an electric current, which turned out to be far more useful than the nonflowing electric charge of static electricity.
At first Volta used bowls of salt solution to produce the flow. The bowls were connected by means of arcs of metal dipping from one bowl to the next, one end of the arc being copper and the other being tin or zinc. Since any group of similar objects working as a unit may be called a battery, Volta's device was an electric battery -- the first in history.
Volta then made matters more compact and less watery by using small round plates of copper and zinc, plus disks of cardboard moistened in salt solution. Starting with copper at the bottom, the disks, reading upward, were copper, zinc, cardboard, copper, zinc, cardboard, and so on. If a wire was attached to the top and bottom of this battery, an electric current would flow when the circuit was closed.
pWatt Fixes the Steam Engine
1764 AD
GLASGOW, SCOTLAND
For half a century, the Newcomen steam engine had been used by miners despite its inefficiency. In 1764, a steam engine of this sort was given to a Scottish engineer, James Watt (1736-1819), to repair.
The repair was easy, but Watt wanted to improve it. He had learned of latent heat from his friend, Scottish chemist Joseph Black (1728-1799), and he realized how wasteful it was to keep heating, cooling, and reheating the same chamber. The thought came to him, then, of having two chambers. One would always be kept hot and the other would always be kept cold. While the steam was doing its work, it would be in the hot chamber, and when it had to be condensed, a system of valves would bleed it into the cold chamber for condensation while more steam was formed in the hot chamber. That was the beginning of the first reasonably efficient steam engine.
-Water, Water Everywhere
580 BC
GREECE
The Greek philosopher Thales (624-546 B.C.) was the first to ask himself what the Universe was made of and to seek an answer that did not depend on gods or the supernatural. He thus represents the birth of rationalism.
His answer, which he may have reached about 580 B.C., was that all matter was fundamentally water, and that everything that did not seem to be water originated in water or was modified water. Water was thus, in his opinion, the primary element (from a Latin word of uncertain meaning), or fundamental substance, of the Earth.
£Hooke Sees Cells
1665 AD
LONDON, ENGLAND
The use of the microscope was spreading rapidly and one of the best of the early microscopists was English physicist Robert Hooke. In 1665 he published Micrographia, which outlined his work in this field. It had some of the most beautiful drawings of microscopic observations ever made.
His most important discovery (though it did not seem so at the time, no doubt) involved the structure of cork. Under the microscope, he found a thin sliver of cork to be composed of a finely serried pattern of tiny rectangular holes. These he called cells, from a Latin word for "small chamber" -- especially one of the type that exists in rows, as monastery cells or prison cells do.
The cells that Hooke observed were empty only because they were found in dead tissue. In living tissue they are filled with fluid, and that disqualifies them from being called cells, strictly speaking. The name, however, clung.
He Wrote the Book on Mechanics
1736 AD
SWITZERLAND
Even Newton clung to ancient conventions when he could. In 1687 he wrote his great book, "Principia," in Latin rather than in English, and although he obtained his results by the use of calculus, he managed to put the proofs into geometric forms in his book.
In 1736, however, the Swiss mathematician Leonhard Euler (1707-1783), the most prolific of all time, wrote the first book -- Mechanics -- to be entirely devoted to that subject. In place of Newton's geometry, he made use of algebra and calculus whenever he could.
jWestern U.S.: Cities and Parks
1990 AD
WESTERN UNITED STATES
Some of the most magnificent sights in the United States are directly below you as you look down from this satellite's eye view of the Western United States.
In addition to the large cities of Los Angeles and San Francisco are the Grand Canyon, Yosemite, the Painted Desert, Bryce Canyon, Zion National Park and many other preserves.
7Powered Flight at Kitty Hawk
1903 AD
KITTY HAWK, NORTH CAROLINA
Once German engineer Otto Lilienthal (1848-1896) had devised his gliders in 1891, it seemed natural to think of putting an internal-combustion engine on a glider as German inventor Ferdinand Adolf August Heinrich von Zeppelin (1838-1917) had done for balloons in 1900. The American astronomer Samuel Pierpont Langley (1834-1906) made the attempt on three separate occasions between 1897 and 1903 and almost succeeded but not quite.
Then two brothers, Orville (1871-1948) and Wilbur (1867-1912) Wright took up the task. They made shrewd corrections in design and invented "ailerons," movable wing tips that enabled the pilot to control the plane. In addition, they built a crude wind tunnel to test their models, and they designed new engines of unprecedented lightness for the power they could deliver.
On December 13, 1903, at Kitty Hawk, North Carolina, Orville Wright made the first powered flight in a heavier-than-air machine. It remained in the air for almost a minute and covered 850 feet. Such devices soon came to be called airplanes.
The X-Ray Revolution
1895 AD
GERMANY
Work on cathode rays by German physicist, Eugen Goldstein (1850-1930) and by British physicist William Crookes (1832-1919) had come to interest a number of physicists in the subject. One of them was a German physicist, Wilhelm Conrad Röntgen (1845-1923), who was particularly interested in the ability of cathode rays to make materials fluoresce.
He placed certain chemicals, known to fluoresce easily, inside a cathode ray tube, surrounded it by dark paper, and darkened the room to observe the pale fluorescence that would result.
On November 5, 1895, he set his cathode-ray tube to working, and in the dimness, a flash of light that did not come from the tube caught his eye. A sheet of paper coated with barium platinocyanide (one of the chemicals he was planning to use) was glowing. The glow ceased when the cathode-ray tube was turned off. The coated paper glowed even in the next room once the cathode-ray tube was turned on.
Radiation was clearly emerging from the tube when the cathode rays were streaming, and was penetrating matter to some extent. Röntgen didn't know what the radiation might be, so he referred to it as X rays, x being the usual symbol for an unknown quantity in mathematics. He published his findings on December 18, 1895.
The news of these X rays roused the world of physics to a furor not seen since Danish physicist Hans Christian Orsted (1777-1851) had discovered electromagnetism. So much work was done, and so many revolutionary findings were made (most of them as a direct result of Röntgen's finding) that Röntgen is often viewed as having set off a second Scientific Revolution, as in 1543 Polish astronomer Nicolaus Copernicus (1473-1543) had set off the first.
For this work, Röntgen received the Nobel Prize in physics (the first one) in 1901.
$Showing 101 is Not 11
810 AD
BAGHDAD, IRAQ
Human beings had been manipulating numbers ever since they had begun writing, about twenty-three centuries earlier. In general, there would be a tendency to make score marks for units, so that 4 would be / / / /. Different marks would be introduced for fives, tens, and fifties, to avoid having to make too many score marks. Or else, as in the case of the Jews and Greeks, letters of the alphabet would be used (which introduced nonsignificant connections between words and numbers and introduced the superstitious folly of numerology).
It might have occurred to someone to use the same numbers for units, tens, hundreds, and so on, merely placing the numbers in different positions for each level, as on an abacus. No one tried this positional notation, however, because no one thought of using a symbol for an abacus level in which no beads had been moved.
For example, if you want to indicate 507 on an abacus, you move 5 beads at the hundreds level and 7 at the units level. You can record the 5 and the 7, but how do you indicate that the tens level hasn't been touched?
About the year 500, some Indian mathematician suggested that such an untouched abacus level be given a special symbol. (Our symbol is 0 and we call it zero.) This meant that you could no longer confuse 507 with 57 or 570. The Arabs may have picked it up from the Hindus about the year 700.
The first important mathematician to make use of this positional notation was an Arab, Muhammad ibn Al-Khwarizmi (780-850), who wrote a book featuring it about 810. (In the book he coined a term that in English became algebra.)
The new system slowly penetrated Europe, which took centuries to give up its clumsy Roman numerals and take up the new Arabic numerals (although, of course, the numerals were Indian to start with). It took centuries to overcome the habit of sticking to something inconvenient but customary rather than adopting something good but new. Still, it was done in the end, and the transition democratized arithmetical computation, bringing it within reach of everyone.
