Galileo Galilei
Explore Galileo Galilei — the Italian astronomer whose telescopic observations and defense of heliocentrism made him the father of modern observational science.
Galileo Galilei (1564–1642) was the Italian astronomer, physicist, and polymath whose work laid the foundations of modern observational science. His telescopic discoveries provided the first visual evidence for the Copernican heliocentric model, and his insistence on observation and mathematics over philosophical authority made him a central figure in the Scientific Revolution.
In 1609, Galileo built an improved telescope and turned it skyward. What he saw shattered the Aristotelian cosmos: the Moon had mountains and craters (it was not a perfect sphere), Jupiter had moons orbiting it (not everything orbited the Earth), Venus showed phases (proving it orbited the Sun), and the Milky Way resolved into countless individual stars. These observations, published in The Starry Messenger (1610), made Galileo famous across Europe.
Galileo's advocacy for the Copernican model brought him into conflict with the Catholic Church. His Dialogue Concerning the Two Chief World Systems (1632), which clearly favored heliocentrism, led to his trial by the Inquisition in 1633. He was found 'vehemently suspect of heresy,' forced to recant, and spent his remaining years under house arrest. Legend has him muttering 'And yet it moves' (Eppur si muove) after his recantation. Whether true or not, the story captures the essential drama: the new science's clash with established authority, and the ultimate triumph of observation over dogma.