The History of Astronomy Part 7 The Debate Concludes Copernicus is Confirmed A Whole New awareness of the Universe

Galileo Galilei (1561-1642) Galileo was an Italian professor of mathematics and astronomy He … developed and used the scientific method demonstrated errors in Aristotle’s theories regarding falling objects, & motion Developed the concept of inertia In 1609 he heard of the invention of the telescope. He soon had built several of his own and turned them on the sky. He discovered:

Mountains on the Moon Galileo’s telescope showed him that the moon was a world like ours It had Mountains, valleys, & great plains It had new features, craters and rays. It also implied that the other planets might also be worlds like ours.

The Phases of Venus Galileo found that Venus has phases like the moon. Oddly the crescent is largest and brightest! (left is Galileo’s actual sketch!) The Ptolemaic model of the universe could not explain it. The Copernican model not only could, but predicted its brightness accurately.

“Its full of stars!” The fact that the Milky Way was made of faint stars established without any doubt that stars were suns at vast and different distances . The Celestial Sphere was shattered. Far away enough that… …parallax can’t be seen with the naked eye! The parallax problem is solved. There was new awareness of the vastness of the Universe

Jupiter’s Moons Galileo discovered the four largest moons of Jupiter He kept track of their orbits, which ran like clockwork This observation led Galileo to doubt Aristotle’s principle of motion and come-up with the idea of inertia. Eventually the motions of Jupiter’s moons was used by Astronomers and mariners as a clock

“The Starry Messenger” Galileo Pays Galileo wrote a book: “The Starry Messenger” which contradicted authorities (Aristotle & Ptolemy) that the Catholic Church had established. Galileo, forced to recant, and put on house arrest for the rest of his life. His works were ordered destroyed in Catholic Countries but they already had reached protestant lands such as England where they would inspire Isaac Newton