Galileo, Galilei

Italian astronomer

Born: Pisa, February 15, 1564

Died: Arcetri (near Florence), January 8, 1642

"And yet it moves ..." - Galileo


Galileo was born 3 days before the death of Michelangelo, passing the torch from fine arts to science. His full name was Galileo Galilei. He was persuaded by his father to study medicine, but after hearing a lecture on geometry, he switched to mathematics and science. He was a true Rennaissance man, with many talents. He experimented with pendulums as a young man, contributing greatly to the development of clocks, and he invented a thermoscope, a gas thermometer, to measure changes in temperature based on the expansion and contraction of gases.

Galileo studied the behaviour of falling bodies and performed the famous experiment at the Leaning Tower of Pisa, simultaneously dropping two cannonballs, one ten times heavier than the other, proving that the rate of fall of a body is completely independent of its weight. This discovery upset the belief in the physics of Aristotle that prevailed at that time, and made Galileo unpopular in Pisa. He moved to a better position in Padua where he became a brilliant lecturer. He corresponded with the astronomer, Kepler, and in 1609, he invented the first telescope with a magnifying power of thirty-two, and turned it upon the heavens. Thus began the age of telescopic astronomy.

Using his telescope, Galileo found that the moon had mountains and the sun had spots. He used these spots to show that the sun rotated about its axis in twenty-seven days, by following individual spots around the sun. He also found that there were many stars in existence that could not be seen with the naked eye. He discovered that Jupiter had four satellites that circled it and was able to work out their periods. The satellites, Io, Europa, Ganymede and Callisto are still known as the Galilean satellites.

Galileo began to publish his discoveries in a periodical he called Siderius Nuncius, the Starry Messenger, arousing both great enthusiasm and profound anger. Galileo was brought before the Pope, Urban VIII, to renounce his heretical views. Legend has it that after he did so, he muttered - "And yet it moves" - referring to the Earth. When he died, in the same year that Newton was born, the conservative faction won a hollow victory by refusing to bury him in consecrated ground. The work of Galileo has, however, prevailed.

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