Galileo Galilei was born in Pisa, Italy, in 1564. His father wanted him to become a doctor and sent him to study medicine at the University of Pisa. While there he discovered a natural talent for math, and eventually left medical school to pursue mathematics. In 1609, Galileo learned about the spyglass, a new invention helping people see distant objects by making them appear closer. This fascinated Galileo and led him to engage his mathematics and engineering talents in a quest to build a more advanced spyglass. He ended up inventing the first telescope. Using the new device, Galileo became the first person to observe the moon up close. He discovered that its surface wasn’t smooth, but actually mountainous and pitted like Earth! Continuing his astronomical research, he used his telescope to establish that small moons circled Jupiter, and he closely observed the rings of Saturn and the phases of Venus.
Galileo’s experiments reinforced his confidence in the Copernican theory stating that all the planets, including Earth, revolve around the sun. This view put Galileo very much in the minority. The Catholic Church strongly endorsed the “geocentric” idea that Earth—God’s Earth, dwelling place of man—was the center of the universe.
When Galileo published his discoveries and openly stated his belief that the Earth circled the sun, he was summoned to Rome. The Vatican accused him of being a nonbeliever opposed to church teachings. Ultimately, though, it decided to spare him from punishment as long as he refrained from publicly advocating for heliocentrism.