The Father of Science, 15 February 1564 – 8 January 1642

Galileo Galilei was an Italian Physicist, mathmatician, astronomer and a philosopher. He became known as ‘The Father of Science’ as he was the first man to confirm the phases of Venus and he also discovered the four largest satellites (moons) of Jupiter. These were later named the ‘Galilean Moons’ in his honour. Galileo’s work remained controversial for many years as the general belief throughout the world of astronomy was that the Earth was the centre of the Universe.

In 1610, Galileo began to publicly announce his theory of heliocentrism (the idea that the sun is the centre of the Universe) when he was met with great opposition from fellow astronomers and clerics who eventually denounced him to the Roman inquisition in early 1615. Although he was cleared of any offense at the time, the catholic church nevertheless condemned his work and he was ordered to stop.

Later, in 1632, he began to defend his work when he published his book ‘Dialogue Concerning the Two Chief World Systems’. He was again tried by the inquisition and found guilty of heresy and spent the rest of his life under house arrest.

Contributions To Astronomy:

In 1581, Galileo began studying at the University of Pisa, where his father hoped he would study medicine. While at the University of Pisa, Galileo began his study of the pendulum while, according to legend, he watched a suspended lamp swing back and forth in the cathedral of Pisa. However, it was not until 1602 that Galileo made his most notable discovery about the pendulum – the period (the time in which a pendulum swings back and forth) does not depend on the arc of the swing (the isochronism). Eventually, this discovery would lead to Galileo’s further study of time intervals and the development of his idea for a pendulum clock.At the University of Pisa, Galileo learned the physics of the Ancient Greek scientist, Aristotle. However, Galileo questioned the Aristotelian approach to physics. Aristotelians believed that heavier objects fall faster through a medium than lighter ones. Galileo eventually disproved this idea by asserting that all objects, regardless of their density, fall at the same rate in a vacuum. To determine this, Galileo performed various experiments in which he dropped objects from a certain height. In one of his early experiments, he rolled balls down a gently sloping inclined plane and then determined their positions after equal time intervals. He wrote down his discoveries about motion in his book, ‘De Motu’, which means ‘On Motion’.

Galileo made his first telescope in 1609, modeled after telescopes produced in other parts of Europe that could magnify objects three times. He created a telescope later that same year that could magnify objects twenty times. Galileo made his most important discoveries in 1610. During this year he discovered Io, Callisto, Europa and Ganymede, the four largest moons of Jupiter. It was also in this year that he discovered the phases of Venus and he noticed that these phases were very similar to those of our moon.

Galileo Facts:

  • Galileo Galilei was born in Pisa, Italy, on the 15th of February 1564, he died on the 8th of January 1642.
  • Galileo was a ground breaking astronomer, physicist, mathematician, philosopher and inventor. Among his inventions were telescopes, a compass and a thermometer.
  • Galileo enrolled to do a medical degree at the University of Pisa but never finished, instead choosing to study mathematics.
  • Galileo built on the work of others to create a telescope with around 3x magnification, he later improved on this to make telescopes with around 30x magnification.
  • With these telescopes, Galileo was able to observe the skies in ways previously not achieved. In 1610 he made observations of 4 objects surrounding Jupiter that behaved unlike stars, these turned out to be Jupiter’s four largest satellite moons: Io, Callisto, Europa and Ganymede. They were later renamed the Galilean satellites in honor of Galileo himself.
  • Famous Galileo quotes include: “In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.”
  • “See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.”
  • “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.”
  • The discovery of these moons was not supported by the scientific principles of the time and Galileo had trouble convincing some people that he had indeed discovered such objects. This was similar to other ideas put forward by Galileo that were very controversial at the time.
  • Galileo refused to believe Kepler’s theory that the moon caused the tides, instead believing it was due to the nature of the Earth’s rotation (helping prove that even the smartest people can make mistakes).

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