A picture, according to Murillo, of Galileo looking at the words “E pur si muove” (“And still moving;” which is not easy to read in this image) is inscribed on the cell wall of his prison. Image via Wikimedia Commons.
Today in Science: February 15, 1564. Happy birthday to Italian astronaut, mathematician and physicist Galileo Galilei. Galileo was one of the first to aim for a telescope in the night sky, where he saw levels of Venus and four dots of light orbiting Jupiter. These and other ideas began to change as we saw the universe and our place in it.
In Galileo’s time, educated people accepted the Aristotelian idea that the Earth was located in the center of an almost unchanged universe. His discovery of a moon orbiting Jupiter (now known as the Galilean satellites in his honor) and Venus’s origins from the planet orbiting the sun were considered a heresy by the Roman Inquisition. In 1633, the Inquisition forced Galileo to recall.
As he left the courtroom, he is notoriously suffocated:
E pur si muove (and still it moves).
The phrase is still used today as retort, meaning it doesn’t matter what you believe; these are the facts.
Galileo spent the rest of his life under house arrest, but that did not stop him from publishing another work, Two New Science, about mechanics and movement.
Galileo grew up in a musical family. In 1574, the family moved to Florence, where 18-year-old Galileo began his education in a monastery. He was very successful in his studies and began studying medicine at the University of Pisa. Due to financial difficulties, he was unable to complete his degree, but his years at university were priceless. They introduced him to mathematics and physics, but most importantly, they introduced him to Aristotle’s philosophy.
Back then, if someone wanted to find out about the universe, the way to do it is to read Aristotle’s works. As Dante put it several centuries before, Aristotle is the “Master of those who know” (Dante, Inferno 4.131). In other words, at that time, there was a knowledge to philosophy of what religion was.
So, despite not being able to complete his degree in medicine and become a university professor, Galileo continued his studies on mathematics. He was able to get some teaching careers for a living. After two years of hard work, he published La Bilancetta (The Little Balance), his first scientific book to gain fame. The book recounted the story of how the king of Syracuse asked Archimedes to determine whether his crown was made of real gold or a mixture of metals at a lower value. Galileo today demonstrated a technique of his “small equilibrium” called “hydrostatic equilibrium,” which is used to make more accurate measurements of differences in density.
Read here about the King’s crown and Archimedes’ other finds.
Galileo’s reputation was shattered after his publication Du Motu (On the Move), a study of falling objects, which showed its disagreement with Aristotelian opinion on the subject.
In 1609, he heard that an instrument had been invented in Holland that displayed distant objects as if they were nearby. Like many others, Galileo quickly mastered the mechanics of the spyglass, but later greatly improved the original design. He gave the Venetian State an eight-powered telescope – a telescope that amplifies a normal eight-hour view. His telescope has doubled his salary and tenure at the University of Padua.
Over the years, Galileo developed his telescope to go up to 20 times.
One of Galileo’s telescopes. Image through University of Oregon.
With his telescope, he made many celestial discoveries. For example, he was the first to see the moon magnified 20 times. He drew the surface of the moon, showing that its surface is bumpy and rocky, contrary to the popular belief of the time that the moon was flat.
In January 1610, he discovered Jupiter’s four largest moons: Io, Europa, Ganymede, and Callisto. Today, they are known as the Galilean moors. He set out what he found in his book Siderus Nuncius (The Starry Messenger).
Galileo noticed that Venus went through stages, just like the moon.
Complex image showing spaceship scenes of Jupiter’s four largest moons. Called the Galilean satellites, they were first seen by the Italian astronaut Galileo Galilei in 1610. Shown from left to right in greater order of distance from Jupiter. Nearest Io is, followed by Europa, Ganymede, and Callisto. Image through NASA.
Galileo was very popular before 1610, but he began to become increasingly public with the heliocentric system causing him trouble with the Catholic Church.
In 1618, Galileo was dragged into a controversy over the nature of the comets, which did not help his social situation. Nevertheless, Galileo published the argument in his own name in Il Saggitore (Am Assayer) in 1623, which to this day is one of his most famous works.
Read selections from Am Assayer.
Things did not improve much for Galileo until his death in 1642. His work continued to go against the accepted Aristotelian idea, and won the wrath of the Catholic Church, which centuries before that he had established a group of institutions within the Church’s judicial system – known as the Inquisition – which aimed to combat heresy.
Notably his 1632 publication of a Discussion about the two main global systems, Copernican and Ptolemaic against Aristotelian opinion. In 1633, the Quest summoned Galileo to Rome. He was identified as a suspected heresy, sentenced to life imprisonment, and formally removed. Nevertheless, he lived comfortably and was allowed to continue with the work.
Galileo ‘s daughter, Sister Maria Celeste, was a nun in the Catholic Church. They wrote each other ‘s letters regularly, and she saved Galileo’ s letters to her, which were last published in a 1999 book by Dava Sobel called Galileo ‘s Daughter.
Despite Galileo’s battles with the church, he was a staunch Catholic. He might be happy to find out that the Vatican has its own observatory and that some of its ancestors are astronauts. But it took until 1992 before the Vatican acknowledged that Galileo was right in his heliocentric beliefs.
Galileo died on January 8, 1642.
Galileo has a long list of finds. While Galileo is highly praised for his various scientific discoveries, he did much more than just push science forward: He also promoted society. His life was much more than just conflict with religion and Aristotelianism. He fought against the eradication of the emerging view of a scientific minority.
Galileo was one of the first to set science free from philosophy. He inspired countless others to pursue the freedom of scientific research.
Portrait of Galileo by Justus Sustermans. Image via Wikimedia Commons.
Bottom line: One of our greatest astronauts, Galileo Galilei, was born February 15, 1564. His discoveries with the improved telescopes he made have changed the way we look at the universe.
