Galileo Galilei, aka Galileo, was an Italian scientist and scholar. He is best known for his groundbreaking work on modern physics and astronomy. With these 40 interesting facts about Galileo, let’s learn more about his inventions, work in astronomy, life, relationship with the church and more…

Facts about Galileo’s early life, education, attraction towards physics and invention of an improved telescope

1. Galileo was the first of six children born to his parents in a Roman Catholic family. From the beginning of his career, he was intelligent and talented.

2. Galileo seriously considered priesthood at a very young age.  However, Galileo’s father wanted him to study medicine at the University of Pisa, for which he enrolled but never completed.

3. In 1585, Galileo had to leave the University of Pisa due to financial concerns. However, he later joined the university as a professor in 1589.

4. Galileo’s contract with the university was not renewed because Galileo was difficult to work with, and, perhaps, because of his inappropriate behavior with his students. Thus, once again he had to leave the University of Pisa and find employment elsewhere.

5. Thereafter, Galileo worked at the University of Padua and gave lectures. There, he made several followers and found his mission in life.

6. His father’s intention behind enrolling Galileo in university for medicine was to help him secure better paying jobs in the field of medicine. Galileo, on the other hand, liked mathematics and physics more than medicine.

7. For a brief period of time, Galileo also worked as an art teacher in the Italian city of Florence.

8. Galileo never married. However, he had three children with Marina Gamba. Two of the children were girls whom Galileo never allowed to marry out of the fear that he would have to pay a hefty dowry. So they were sent to convent and ended up becoming nuns.

9. The most important of Galileo’s inventions is the telescope. However, it is a little-known fact that Galileo was not the first person to invent it. He got the idea for a telescope from Dutch spectacles makers who had invented a spyglass to observe ships. Galileo used the idea to make his own improved telescope with much higher magnification, which he sold to Venetian merchants for spotting ships.

10. Galileo built the first of his telescopes in 1609.

Galileo said, “Facts, which at first seem improbable, will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty.”

11. Another incorrect fact about Galileo is that he was the first to use a telescope to view the sky. Note that Thomas Harriot, an Englishman, was the first to observe the sky with a telescope. However, the only difference between the two is that Galileo also made some important conclusions with his observations of the sky, which Harriot was unable to make. Galileo became famous for his observations that gave the world a better understanding of celestial bodies.

12. In 1610, Galileo was the first astronomer to discover the four moons of Jupiter. These moons were named “Galilean moons” after him. The four moons associated with “Galilean moons” are lo, Europa, Ganymede and Callisto. The largest of the “Galilean moons” is Ganymede. Thus, he discovered the first moons ever known to orbit a planet other than Earth.

13. With his telescopes, Galileo studied the moon, Venus and Jupiter.

14. After 400 years, Galileo’s telescope still survives, and is available in the Istituto e Museo di Storia della Scienza in Italy. The museum has two telescopes and objective lenses, which were built by Galileo himself.

Facts about his house arrest, becoming blind and writing books

15. Did you know that Galileo was kept under house arrest for eight years during the later portion of his life? His period of house arrest occurred between 1634 and 1642, during which time he wrote a book before becoming blind. The book contained the summary of his life’s work, science of motion and strengths of materials. He named the book – “Two New Sciences.”

16. Galileo could not publish his book during the time he was under house arrest. However, it was published in Holland in 1638. Alas, Galileo had become blind and severely ill by this time.

17. It is said that Galileo went blind because he used to observe the sun for long stretches of time while he was looking at sun spots with his telescope.

18. Galileo was a prominent scientist of the 17th century, as he made a number of important contributions during that time.

19. He is dubbed “the father of observational astronomy,” “the father of modern physics” and “the father of modern science.”

20. Galileo conducted a 20-year-long study on the science of motion (kinematics), and published a book called “The Little Balance.”

21. If you are a fan of Albert Einstein, or if he is your favorite scientist, you should know that Galileo was Albert Einstein’s favorite scientist.

In Galileo Galilei’s honor

22. America launched an unmanned spacecraft named “Galileo” in the memory of this great astronomer. The spacecraft was tasked to study Jupiter and its four moons.

23. Europe developed a global satellite system of civil navigation and named it “Galileo” in honor of the great scientist of the 17th century.

Facts about Galileo’s other inventions

24. Galileo is also credited with the invention of the military compass, which was used as a calculating device between the 16th and 19th centuries. In addition to the compass, he also invented a thermometer.

25. Galileo also established that in the absence of air resistance, gravity accelerates all objects equally, irrespective of their masses.

26. Galileo was a supporter of “heliocentrism”, an astronomical model where the Sun is the center of the solar system with the Earth and other planets revolving around it.

27. Galileo was the first person to reveal that the Milky Way was composed of stars.

28. Newton’s first law of motion was based on Galileo’s formulation of the concept of inertia. Galileo stated that an object in a state of motion possesses an “inertia” that causes it to remain in that state of motion unless an external force acts on it. Because of this, it is easy to understand why Galileo was called “the father of modern physics” and “the father of modern science.”

29. Galileo’s work, which was opposed by the church during his lifetime, was recognized by the church after his death. In the modern era, 20th century Popes Pius XII and John Paul II made official statements of regret for the church’s treatment of Galileo.

30. Galileo was against Kepler’s theory that the moon caused tides on the Earth, and instead believed that they were due to the rotation of Earth. Surprisingly, Kepler supported Galileo for his work by publishing letters in his support at the time.

31. During his final years when he was blind, Galileo quoted: “Alas! Your dear friend and servant Galileo has been for the last month hopelessly blind; so that this heaven, this earth, this universe, which I by my marvelous discoveries and clear demonstrations had enlarged a hundred thousand times beyond the belief of the wise men of bygone ages, henceforward for me is shrunk into such a small space as is filled by my own bodily sensations.”

32. His book, Sidereus Nuncius or The Starry Messenger, was first published in 1610, making him famous.

Interesting facts about Galileo’s telescope

Galileo's telescope
Galileo’s telescope. Image credit – University Today

33. Galileo developed a crude refracting telescope at first.

34. His telescope was initially able to magnify only 8x. However, he soon refined it to provide 20x magnifications.

35. The telescope had a convex objective lens and a concave eyepiece in a long tube.

36. His telescope had a very narrow field of view. With it, he could only view about half the width of the moon.

37. He used his telescope to study the moon quite effectively. He concluded that the moon is uneven, rough, and crowded with depressions and bulges. He could also calculate the heights of the mountains on moon by measuring the lengths of their shadows and applying geometry.

38. Another interesting fact about Galileo is that Isaac Newton was born the same year Galileo died. Newton did a lot of work on the motion of bodies, and took Galileo’s ideas forward, presenting to the world the fundamental equations and data we use in our daily lives.

39. Because of church opposition regarding his promotion of the theories supporting heliocentrism, Galileo had to adopt a principal of a “double truth,” publicly disowning his convictions, while remaining privately and intimately convinced of the truth in his theories.

40. Galileo’s book, the Dialogue Concerning the Two Chief World Systems was banned by the church at that time. However, the ban on the book was lifted in 1835 by the church some 200 years after its original publication.

Famous quotes by Galileo Galilei

  1. “I do not feel obliged to believe that the same God who has endowed us with sense, reason and intellect has intended us to avoid their use.”
  2. “You cannot teach a man anything; you can only help him find it within himself.”
  3. “All truths are easy to understand once they are discovered; the point is to discover them.”
  4. “By denying scientific principles, one may maintain any paradox.”
  5. “I have never met a man so ignorant that I couldn’t learn something from him.”
  6. “In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.”
  7. “Passion is the genesis of genius.”
  8. “Philosophy is written in that great book which ever lies before our eyes — I mean the universe — but we cannot understand it if we do not first learn the language and grasp the symbols, in which it is written”
  9. “They seemed to forget that the increase of known truths stimulates the investigation, establishment and growth of the arts; not their destruction.”
  10. Thought is the most pleasing ability granted to human kind.”

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Quick facts about Galileo Galilei

Born15 February 1564
Pisa, Duchy of Florence, Italy
Died8 January 1642 (aged 77)
Arcetri, Grand Duchy of Tuscany, Italy
Languages KnownItalian
Age at the time of death77 years
Field of WorkAstronomy, physics, engineering, natural philosophy, mathematics
Known forKinematics
Telescopic observational astronomy
ContributionsScience and Physics