4. Development of the atomic bomb (1940's)

The first atomic bomb, based on uncontrolled nuclear fission, was tested on July 16, 1945. This test marked the beginning of the Atomic Age. Later, controlled nuclear fission led to the use of nuclear energy for peaceful purposes. While there were problems, such as those at Three Mile Island in the United States, controlled nuclear fission currently accounts for approximately one-fifth of the electric power generated in the United States. Radiation produced by radioactive nuclei became extremely useful for scientific research, medical diagnosis, and treatment of some forms of cancer.

During the next century, scientists hope to develop controlled methods of nuclear fusion to produce atomic energy. Nuclear fusion is the source of the sun's energy and, unlike nuclear fission, does not produce large quantities of radioactive waste. Because nuclear fusion uses the hydrogen atoms of water as fuel, energy produced by fusion could be essentially inexhaustible.

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Marianna A. Busch is the Chair and a Professor in the Department of Chemistry at Baylor University. Her Top 10 list centers on the most important scientific events of the 1900's. She discusses what these events meant to scientists and society in general. She calls attention to a number of the groundbreaking scientists who left their mark on the world of science in this century.

1.

The discovery of the molecular structure of DNA (1953)

2. The invention of the transistor (1947)
3. The first use of penicillin (1928)
4.

Development of the atomic bomb (1940's)

5. The launch of Sputnik I by the Soviet Union (Oct. 4, 1957)
6. Construction of the first laser (1960)
7. The development of new plants and the Green Revolution (mid-1900's)
8. The beginning of nuclear physics (early 1900's)
9. The development of quantum theory (early 1900's)
10. The publication of Silent Spring (1962)