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Telescopes from the Ground Up
Portrait of Galileo Galilei Courtesy Royal Astronomical Society.

Galileo Galilei was a questioner. He first started making a name for himself as a math professor in Pisa, Italy. As the story goes, in 1590 he brought a group of his students up to the top of a tower and dropped balls of different weight off the top. The Greek philosopher Aristotle had declared that objects of different weight would hit the ground at different times. Galileo proved that they would hit the ground at the same time, no matter what their weight.

Galileo had taken common knowledge and proven it wrong by testing it, or experimenting. In 1609, he would do it again when he turned a telescope to the sky and discovered that the Moon had mountains and valleys, that the sky was full of more stars than the eye could see on its own, and that planets were dots that could be objects just like the Moon and the Earth —orbited by their own moons.

Galileo’s discoveries convinced him that the Sun was the center of the solar system, a belief that put him at odds with the powerful Catholic Church. Galileo was brought to trial and forced to take back his statements that the Sun was at the center. Though he spent the rest of his life under house arrest, he continued his work and research until his death.


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