Galileo

Galileo

During the early 1600's, the great Italian scientist Galileo was the first person to use a telescope to study the sky. Galileo's observations helped confirm the Copernican system. For example, he found that several moons revolve around Jupiter. This discovery showed that, contrary to the theories of Aristotle and Ptolemy, not all bodies revolve around the earth.

Galileo stressed the need for carefully controlled experiments. In his research, Galileo used observation and mathematical analysis as he looked for cause and effect relationships among natural events. He recognized that experimentation could lead to the discovery of new principles. For example, Aristotle had taught that the heavier an object is, the faster it falls to the ground. Galileo questioned that idea. He set up experiments to find the true laws of falling bodies and proved that Aristotle was wrong. Through experimentation, Galileo discovered many basic principles of mechanics.

Excerpt adapted from the "Astronomy" and "Science" articles, The World Book Encyclopedia © 1999