Galileo Galilei

Galileo was born in Pisa in 1564, the son of a musician, and taught mathematics at Pisa and then Padua. He was quarrelsome, brilliant, and convinced that the book of nature was written in the language of mathematics.

When he improved the newly invented telescope and turned it on the sky, he saw mountains on the Moon, four moons circling Jupiter, and the phases of Venus — evidence that the heavens were neither perfect nor fixed to the Earth. His Dialogue Concerning the Two Chief World Systems defended Copernicus as a conversation between three speakers, and its arguments were so plainly one-sided that the Inquisition summoned him.

Tried in 1633, he was forced to abjure the motion of the Earth and spent his last years under house arrest at Arcetri, where he wrote the Two New Sciences and laid foundations for the physics of motion. He died in 1642.

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