Today in science: Galileo's birthday | Human world

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Portrait, attributed to Murillo, of Galilee observing the words "E pure si muove" ("And yet, it moves," is illegible in this image) scratched on the wall of his prison cell. Image via Wikimedia Commons.

February 15, 1564. It was on this date that was born the astronomer, mathematician and Italian physicist Galileo Galilei. He is one of the first peoples on Earth to have directed a telescope to the sky, where he discovered, among other things, phases for the planet Venus and four star-shaped luminous points in orbit around the planet Jupiter. At the time of Galileo, educated people subscribed to the Aristotelian vision that the Earth is at the center of a more or less immutable universe. Thus, the discovery of the moons in orbit around Jupiter (now called the Galilean satellites) and the revelation that Venus must orbit around the sun, not the Earth, were considered heresy by the Roman Inquisition. In 1633, the Inquisition forced Galileo to retract. He spent the rest of his life under house arrest.

Then he would have said:

E pure if muove (and yet it moves).

The phrase is still used today as a replica, involving no matter what you believe; these are the facts.

Galileo grew up in a family of musicians. In 1574, the family moved to Florence where Galileo, 18, began his studies in a monastery. He was very successful in his studies and started studying medicine at the University of Pisa. Due to financial problems, he could not finish his studies, but his years at the university were invaluable. They introduced him to mathematics and physics, but especially to Aristotle's philosophy.

At the time, if anyone wanted to know more about the universe, one had to read the works of Aristotle. As Dante said a few centuries ago, Aristotle is "the master of those who know" (Dante, Inferno 4.131). In other words, at that time, knowledge was to philosophy what faith was to religion.

Thus, despite the impossibility of obtaining his medical degree and becoming a university professor, Galileo nevertheless continued his mathematics studies. He was able to earn a few minor teacher positions. After two years of hard work, he published The bilancetta (The little balance), his first scientific book that earned him a reputation. The book commented on the story of how the king of Syracuse asked Archimedes to check whether his crown was pure gold or a mixture of lower value metals. Galileo presented one of his inventions, the "small balance", now called "hydrostatic equilibrium", which allows for more precise measurement of density differences.

Read here about the king's crown and the other findings of Archimedes.

Galileo's reputation was bruised after the publication of his From Motu (Moving), a study of falling objects, which shows his disagreement with the Aristotelian view of the subject.

In 1609, he heard that in the Netherlands, an instrument had been invented that showed distant objects as if they were close. Like many others, Galileo quickly understood the mechanics of the telescope, but he later greatly improved the original design. He presented to the Venetian State an eight-motor telescope – a telescope that magnifies normal vision eight times. His telescope allowed him to double his salary and stay for life at Padua University.

Over the years, Galileo has upgraded his telescope until it grows up to 20 times.

With his telescope, he made many astronomical discoveries. For example, he was the first to see the moon magnified 20 times. He traced the surface of the moon, showing that its surface is bumpy and rocky, contrary to the popular belief that the moon was smooth.

In January 1610, he discovers the four most massive moons of Jupiter: Io, Europa, Ganymede and Callisto. Today, they are called the moons of Galilee. He exposed all his discoveries in his book Siderus Nuncius (The sidereal messenger).

Galileo observed that Venus had gone through phases, just like the moon.

Composite image showing spacecraft views of the four largest moons of Jupiter. Known as Galilean satellites, they were first seen by the Italian astronomer Galileo Galilei in 1610. Represented from left to right in ascending order of Jupiter's removal. Io is the closest, followed by Europa, Ganymede and Callisto. Image via NASA.

In 1610, Galileo was a highly respected man, but his increasingly public acceptance of the heliocentric system was beginning to cause him trouble with the Roman Catholic Church.

In 1618, Galileo was embroiled in a controversy over the nature of comets, which did not help his social position. Galileo nevertheless published the argument under his own name in Il Saggitore (The tester) in 1623, which is to this day one of his best-known works.

Read the selections of The tester.

Things did not go much better for Galileo before his death in 1642. His work constantly challenged the vision accepted by Aristotle and earned him the wrath of the Roman Catholic Church, which had founded a group of centuries ago. Institutions in the judicial system of the Church known as the Inquisition – whose purpose was to combat heresy.

In particular, its publication in 1632 of Dialogue on the two main world systems, Copernican and Ptolemaic opposite to the Aristotelian view. In 1633, the Inquisition summoned Galileo to Rome. He was declared a heretic suspect, punished with life imprisonment and forced to formally abjure. Nevertheless, he lived comfortably and was allowed to continue his work.

Galileo has never stopped working. In 1634, his beloved eldest daughter, Virginia, passed away. He was 70 years old. He decided to finish what he had started before the telescope stopped him. He collected and completed his unpublished studies, and in 1638 published them in Dialogues about two new sciences, discuss the kinematics and properties of materials.

Galileo died on January 8, 1642.

The list of all discoveries of Galileo is very long. Although Galileo is greatly commended for his various scientific discoveries, he has done much more than simply advance science: he has also advanced society. His life was much more than a conflict with religion and Aristotelianism. It was a fight against the removal of the opinion of an emerging scientific minority.

Galileo was one of the first to liberate the science of philosophy. It has inspired countless other people to pursue the freedom of scientific investigation.

Portrait of Galileo by Justus Sustermans. Image via Wikimedia Commons.

Conclusion: Galileo was born on February 15, 1564. He was one of the first to aim at the sky with a telescope, thus showing that the Earth is not the center of all things in the universe .