Galileo Galilei: Biography, Facts, & Things You Don't Know Yet

People | February 15, 2021

Italian astronomer and physicist Galileo Galilei (1564–1642) using a telescope, circa 1620. (Hulton Archive/Getty Images)

Much like Madonna and Cher, Galileo was a thought leader so revolutionary that we know him by only his first name. He made major contributions to the fields of astronomy and mathematics, but he made a powerful enemy of the Catholic Church and even narrowly avoided being burned at the stake for suggesting that perhaps the secrets of the universe expanded beyond what was known in medieval times.

Galileo's Early Years

Galileo Galilei was born in 1564 in Pisa, Italy as the oldest of Vincenzo Galilei's six children. Galileo turned out to be so bright and inquisitive that he enrolled in the University of Pisa when he was only 16 years old, intending to study medicine before discovering a new passion in mathematics. He was especially interested in how math explains the movement of objects, and within just two years, he published his first formula describing the natural laws regarding the movement of pendulums. Although he never completed his schooling, Galileo served as the head of the mathematics departments at the Universities of Pisa and Padua, where he conducted a series of experiments on the speed and acceleration of falling objects, including his famous climb to the top of the Leaning Tower of Pisa to prove that objects of different weights dropped from its height would reach the ground at the same time.

Galileo's "cannocchiali" telescopes at the Museo Galileo, Florence. (Sailko/Wikimedia Commons)

Galileo's Telescope

Galileo didn't invent the telescope, but he greatly improved upon its design. The first telescope he built in 1609 was more powerful than any before, and the next year, he discovered four celestial objects orbiting Jupiter that he assumed were stars but were in fact the planet's four largest moons. He also observed details on the surface of Earth's moon and numerous stars he'd never seen before, publishing his findings in a book called The Starry Messenger.

Galileo understood the importance of wealthy patrons, so he used The Starry Messenger to kiss up to the powerful Medici family by suggesting that the newly observed star cluster be named the Medician Stars. As a result, Cosimo Medici named Galileo the official philosopher and mathematician of the Medici family, and his association with them gave him a platform to advance his scientific theories.

Cristiano Banti's 1857 painting Galileo Facing The Roman Inquisition. (Cristiano Banti/Wikimedia Commons)

The Roman Inquisition

In Galileo's time, science was deeply entwined with philosophy and religion. Aristotle's declaration that the Earth was the center of the universe was accepted as fact. The religious community in particular liked this idea because it offered proof that the Earth was a unique and special place created by God, but science was starting to force people to question these traditional ideas. One controversial new idea was that the Sun was the center of the galaxy, which was considered blasphemy by the Catholic Church.

When Galileo published his book Dialogue Concerning The Two Chief World Systems in 1632, he tried to present the heliocentric and geocentric arguments equally, but considering other viewpoints wasn't really the Church's bag, so Galileo was summoned to the Roman Inquisition. He was accused of heresy, threatened with death, and given the opportunity to recant his beliefs to save himself from the stake. Having seen what happened to people who refused, Galileo took the deal, publicly expressing his regret and insisting his heliocentric conclusions were the result of faulty data and calculations.

Middle finger of Galileo's right hand. (Sailko/Wikimedia Commons)

Galileo's Later Life And Beyond

Galileo was spared a fiery death but forced to live out the remainder of his days under house arrest. He died of natural causes on January 8, 1642 at the age of 77. He never married but had three children with Marina Gamba, and even though Galileo ran afoul of the Catholic Church, his two daughters both joined a convent in Florence and became nuns. His son, named after his grandfather, exhibited the older man's musical talents and became a lute player.

Galileo's writings were banned by the Catholic Church until 1744, but he was decidedly on the right side of history. Two 2oth-century popes, Pius XII and John Paul II, officially apologized for the Church's treatment of the scientist, but on March 12, 1737, nearly 100 years after Galileo's death, he got a more ghoulish and profane vengeance. Historian Anton Francesco Gori removed the skeletal middle finger from his corpse, which is now on display at the History of Science Museum in Florence, pointing upward in supplication to the viewer to look to the heavens or in eternal defiance of those who oppressed him, depending on your interpretation.

Tags: famous people | Italy | science

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Karen Harris


Karen left the world of academic, quitting her job as a college professor to write full-time. She spends her days with her firefighter husband and four daughters on a hobby farm with an assortment of animals, including a goat named Atticus, a turkey named Gravy, and a chicken named Chickaletta.