Galileo turned a Dutch spyglass idea into a tool that reshaped the heavens
A lutenist's son who dropped medicine for mathematics, Galileo heard of a Dutch spyglass in 1608 and within a year had built his own. Pointing it upward, he saw mountains on the Moon and four moons circling Jupiter. His defence of a Sun-centred cosmos later cost him his freedom.
The eldest of six children, Galileo arrived on 15 February 1564 in Pisa, a Florentine possession at the time. His father Vincenzo was a leading lutenist, composer and music theorist in the Florentine Camerata, the circle that paved the way for opera, and Galileo became a skilled lute player too. Supporting his youngest brother Michelangelo, another musician, and paying his sisters' promised dowries weighed on him financially, which may explain his early interest in money-making inventions.
He considered becoming a priest but enrolled at Pisa to study medicine in 1580. While a student he watched a chandelier swinging in wide and narrow arcs and, timing it against his pulse, concluded each swing took the same time. He took the Pisa chair of mathematics in 1589, then taught geometry, mechanics and astronomy at Padua from 1592 to 1610. Observing Kepler's Supernova in 1604 and finding no parallax, he argued such new stars lay far off, undermining the Aristotelian idea that the heavens never change.
In 1609 he built a telescope magnifying about three times, later reaching roughly thirty. On 30 November he turned it on the Moon; Thomas Harriot in England had looked months earlier, but Galileo worked out that the ragged shadows came from mountains and craters and estimated their heights. From 7 January 1610 he tracked three, then four, points near Jupiter that shifted nightly: moons, not fixed stars. He also saw the phases of Venus, sunspots and Saturn's rings, and built an early microscope.
Backing Copernican heliocentrism brought an Inquisition inquiry in 1615. His 1632 Dialogue Concerning the Two Chief World Systems seemed to mock Pope Urban VIII, a former supporter, and he was convicted as vehemently suspect of heresy, forced to recant, and confined to house arrest for life. There he wrote Two New Sciences in 1638. He died on 8 January 1642. He had three children with Marina Gamba; his daughters became nuns at Arcetri.
Source: Galileo Galilei
