On this day in 1633, Italian astronomer and physicist Galileo Galilei (1564–1642) was forced by the Roman Catholic Church to recant his discovery that the Earth orbits the sun. At the time, Church doctrine claimed the Earth was the center of the universe.

“In questions of science,” he wrote, “the authority of a thousand is not worth the humble reasoning of a single individual.”

In 1609, Galileo crafted the first telescope for studying the heavens. With his 30-power spyglass, he discovered four moons circling Jupiter, studied Saturn, and observed the phases of Venus. He documented sunspots and the rugged terrain of the moon—evidence that defied Aristotle’s claim of celestial perfection and supported the model of Copernicus.

Despite being warned to stop, Galileo continued to write about his discoveries until he was arrested and convicted of heresy. Sent into exile, he lived out his final years under house arrest.

A heavenly beacon of intellect and bold inquiry, Galileo helped create the foundation for modern science. He remains one of history’s most original geniuses.

“You cannot teach a man anything; you can only help him to find it within himself,” he said.

The Church lifted its ban on his Copernican dialogue, The Dialogues, in 1822—nearly two centuries too late, but not too late to affirm the truth he saw in the stars.