Galileo Galilei, lived in Pisa home of the tall leaning tower — just right for an experiment challenging Greek philosopher Aristotle.
View of Pisa from the Leaning Tower of Pisa
Aristotle said that a heavier object falling from the same height, at the same time, would travel faster than a lighter object. Galileo disagreed. He said both objects would reach the ground about the same time.
It is said that at the top of the tower, Galileo dropped two spherical objects, one heavier than the other, perhaps a cannonball and a musketball. Both hit the ground at about the same time, disproving Aristotle’s law of gravity. Whether this actually occurred, or it was instead a thought experiment, Galileo wrote about it in his book, On Motion.
The Leaning Tower of Pisa
In Pisa, disproving Aristotle did not win fans for Galileo, and he was no longer asked to teach at the university there. But he wasn’t done challenging Aristotle. This time the challenge took place in the sky above.
The Dutch invented a telescope that made faraway objects appear closer. Galileo knew he could improve the Dutch telescope. When he did, he discovered that he could see the actual surface of the moon. It was not at all as Aristotle described it — completely smooth. Instead, the surface had peaks and valleys.
Galileo and his telescope
With his telescope, he also discovered the largest of Jupiter’s four moons. He published his discoveries in his book, Starry Messenger. Europeans learned about Earth’s moon and Jupiter’s moon, and Galileo became famous. He was invited by the Grand Duke of Tuscany to live in Florence and spend his days searching the sky for new discoveries.
What he discovered again challenged Aristotle. Aristotle said that our solar system was Earth centered. The sun and other planets revolved around the Earth.
What Galileo observed through his telescope made him realize that Aristotle was wrong. The sun was at the center of our solar system and the earth, like the other planets, revolved around it.
