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How Galileo Fought the Catholic Church and Became the First Superstar Scientist

Patrick J. Kiger 5-6 minutes 12/9/2020

Galileo was born in Pisa, Italy in 1564, one of six or seven children of a musician named Vincenzo Galilei, according to Rice University's Galileo Project website. In Galileo's youth, his family moved to Florence.

After getting his early education at a monastery, Galileo was sent by his father in 1581 to the University of Pisa, where he was supposed to earn a medical degree, as this biographical profile details. But Galileo didn't have much interest in healing the human body. Instead, he was curious about the world around him, and started physics experiments — some of them challenging the views of the classical Greek philosopher Aristotle. In 1585, he left the university without earning a degree, and began teaching mathematics, another of his interests. Eventually, his reputation grew so much that in 1589, he was invited back to the university to head the math department.

In 1592, Galileo moved to Venice and took a better-paying post at the University of Padua, where he spent the next 18 years teaching math and astronomy. During that time, he began a relationship with a woman named Marina Gamba, with whom he eventually had two daughters and a son.

 Galileo
Galileo's telescope, which he made in 1610, from the collection of the Museo Galileo in Florence, Italy.

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In 1609, while still at the university, Galileo heard about a Dutchman who had visited Venice and shown off a new invention, the telescope. Galileo decided to make his own, better version, and taught himself how to grind lenses to an even higher magnification.

"He was an excellent craftsman who read descriptions of the instrument and made the most powerful telescopes at the time," Alan Hirshfeld writes in an email. He's a physics professor and director of the UMass Dartmouth Observatory, and author of the 2014 book "Starlight Detectives: How Astronomers, Inventors, and Eccentrics Discovered the Modern Universe."

"[Galileo] could see what others could not, and therefore his observations were groundbreaking," Hirshfeld explains.

Perhaps the most important of Galileo's astronomical discoveries were his revelations about the moon's topography, and how its mountains, valleys and plains are comparable to those on Earth. "It's a material world in space, not some special celestial body made of divine substance," Hirshfeld says.

Galileo's discovery of Jupiter's moons was another breakthrough. As Hirshfeld explains, he also found that the moons "keep up with Jupiter as it moves, whether it moves around the Earth or around the sun, depending on one's beliefs, but Jupiter's moons do not get left behind as critics of Copernicus claimed our moon would if Earth were moving around the sun. Jupiter and its moons provide a model of what the solar system is like: small bodies orbiting the larger body."

Galileo also observed that the Milky Way galaxy consists of stars, most of which are too faint to be seen individually by unassisted human eyes. Thanks to him, humans learned that "There are many more stars than previously believed, and our cosmos might be far larger than we thought," Hirshfeld says.

He also discovered that the planet Venus had changing crescent phases.

"The observation that Venus went through a full cycle of phases, from new to crescent to full and back was totally incompatible with the geocentric model of the universe," says Larry Marschall, an emeritus professor of physics at Gettysburg College, in an email. "It could only be explained if Venus went around the sun in an orbit that was smaller than the Earth's orbit around the sun — in other words the Copernican model."

Galileo Galilei
Galileo defended himself before the Holy Office in the Vatican in 1632 after he was condemned by the Tribunal of the Inquisition for having defended the theories of Copernicus. Painting by Joseph Nicolas Robert-Fleury, 1847, Louvre Museum, Paris.

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