Galileo Dies Under House Arrest: Science Unbowed

Galileo didn't invent the telescope, but he was the first to point one at the sky and understand what he was seeing. Moons orbiting Jupiter. Mountains and craters on the Moon. More stars than anyone had counted. Phases of Venus that could only be explained if Venus orbited the Sun, not the Earth. He published his observations in a short book called Sidereus Nuncius in March 1610, and within weeks the old model of the universe was in trouble. Born in Pisa on February 15, 1564, Galileo studied medicine before switching to mathematics and physics. He taught at the University of Padua for eighteen years, where he conducted experiments on motion and mechanics that challenged Aristotelian physics. He demonstrated that objects of different weights fall at the same rate, contradicting two thousand years of accepted wisdom. When he heard in 1609 that a Dutch optician had built a device that made distant objects appear close, he built his own version within days and improved it to roughly 20x magnification. He turned it skyward and what he found was devastating to the Ptolemaic geocentric model: Jupiter had its own moons, proving that not everything orbited Earth. The Milky Way resolved into individual stars. The Moon was rough and cratered, not the perfect sphere Aristotle described. He published his support for the Copernican heliocentric model in Dialogue Concerning the Two Chief World Systems in 1632, structured as a conversation between three characters. The one defending the geocentric view was named Simplicio. Pope Urban VIII, who had been Galileo's friend and supporter, took it personally. The Inquisition called him to Rome in 1633, when he was 69 years old and suffering from hernia and insomnia. He was shown the instruments of torture. He recanted. The sentence was house arrest for the remainder of his life. He spent it at his villa in Arcetri, near Florence, going slowly blind, and published his most important scientific work, Discourses on Two New Sciences, which laid the groundwork for Newtonian mechanics. He died on January 8, 1642, at 77. The story that he muttered "And yet it moves" as he left the Inquisition is almost certainly apocryphal. But he was right.