Galileo Born: Father of Modern Observational Science

Galileo Galilei was born on February 15, 1564, in Pisa, the eldest of six children in a family of Florentine musicians and cloth traders. His father, Vincenzo Galilei, was a lutenist and music theorist whose experimental approach to understanding sound influenced his son's later insistence on observation and measurement over received authority. Galileo enrolled at the University of Pisa to study medicine at his father's insistence, but abandoned the degree after discovering mathematics. He was seventeen when he noticed a chandelier swinging in the Pisa cathedral and timed its oscillations against his own pulse, observing that the period remained constant regardless of the arc's width. He never published a paper on pendulums; he simply filed the observation away. In 1609, he learned of a new Dutch optical device and built his own improved version, a telescope, which he turned toward the sky. What he saw demolished fifteen centuries of Aristotelian cosmology. Jupiter had four moons orbiting it, not the Earth. The Moon's surface was rough and cratered, not the perfect sphere Aristotle had described. Venus showed phases like the Moon, proving it orbited the Sun. He published these findings in Sidereus Nuncius in 1610, and the book made him the most famous scientist in Europe. The Catholic Church caught up with him in 1633. Threatened with torture by the Inquisition, he recanted his support for the Copernican model that placed the Sun at the center of the solar system. He spent his remaining nine years under house arrest at his villa in Arcetri, outside Florence. He continued working. He discovered the Moon's libration while confined. He went completely blind in 1638 and spent his final four years dictating scientific observations and mathematical proofs to his students. He died on January 8, 1642.