Galileo's Scientific Career

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Galileo's Scientific Career

Beggining Of His Scientific Career

He created the thermoscope, which was the forerunner to the thermometer. In 1586, he also published a brief book detailing the design of a hydrostatic balance he had built, which brought him to the attention of the scholarly world. Galileo applied for a chair of mathematics at the University of Bologna in 1588, but his application was turned down. However, his reputation grew, and later that year he was invited to give two lectures to the Florentine Academy, a prestigious literary club, on the layout of the world in Dante's Inferno. He also discovered several remarkable theorems on centers of gravity which were delivered in a manuscript, earning him the respect of mathematicians and the support of Guidobaldo del Monte (1545–1607), a nobleman and author of several major works on mechanics. In 1589, he was appointed chairman of mathematics at Pisa. [1] [2] [3] [4] [5] [6] [7]

The University Of Padua

When his father died in 1591, he was left in charge of the family's financial burdens. In 1592, he went to the University of Padua, where he taught geometry, mechanics, and astronomy until 1610. He'd later consider these to be his best years. During this time, Galileo made important discoveries in both pure fundamental science and practical applied science. Between 1595 and 1598, Galileo created and improved a geometric and military compass for gunners and surveyors. This built on the previous work of Niccol Tartaglia and Guidobaldo del Monte, who designed instruments. It gave gunners a new and safer way of accurately elevating cannons, as well as a quick method of calculating the charge of gunpowder for cannonballs of various sizes and materials. As a geometric instrument, it could construct any regular polygon, compute the area of any polygon or circular sector, and perform a variety of other calculations. Under Galileo's direction, instrument maker Marc'Antonio Mazzoleni produced more than 100 of these compasses, which he sold for 50 lire and offered a course of instruction in their use for 120 lire. His varied interests included the study of astrology, which was a discipline linked to mathematics and astronomy at the time. Tycho Brahe and others observed the supernova of 1572. Ottavio Brenzoni, in a letter dated 15 January 1605, brought the 1572 supernova and the less bright nova of 1601 to Galileo's attention. Galileo witnessed and discussed Kepler's Supernova in 1604. Galileo deduced that these new stars were distant because they lacked detectable diurnal parallax, thereby disproving Aristotle's belief in the immutability of the heavens.

Galileo's Telescope

Galileo built a telescope with about 3x magnification the following year based solely on hazy descriptions of the first practical telescope, which Hans Lippershey attempted to patent in the Netherlands in 1608, Later, he improved the models so that they could magnify up to 30 times. A Galilean telescope, also known as a terrestrial telescope or a spyglass, allowed the observer to see magnified, upright images of the Earth. He could also use it to observe the sky; for a time, he was one of the few people who could build such telescopes. Galileo used his refracting telescope to discover that the Moon's surface is not smooth in late 1609. On August 25, 1609, he demonstrated one of his early telescopes, which had a magnification of about 8 or 9, to Venetian politicians. Galileo's telescopes were also a profitable sideline for him, as he sold them to merchants who found them useful at sea as well as as trade items. A Greek mathematician named Giovanni Demisiani coined the term "telescope" for Galileo's instrument at a banquet held in 1611 by Prince Federico Cesi to make Galileo a member of his Accademia dei Lincei. Galileo published his first telescopic astronomical observations in a brief treatise titled Sidereus Nuncius in March 1610. (Starry Messenger). In it, he stated:
"On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavens through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet; and although I believed them to belong to a number of the fixed stars, yet they made me somewhat wonder, because they seemed to be arranged exactly in a straight line, parallel to the ecliptic, and to be brighter than the rest of the stars, equal to them in magnitude . . . When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night. I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter."
On November 30, 1609, Galileo pointed his telescope at the Moon. While Galileo was not the first to use a telescope to observe the Moon, he was the first to attribute the uneven waning to light occlusion caused by lunar mountains and craters. In his study, he also made topographical charts to estimate the heights of the mountains. The Moon was not a translucent and perfect sphere, as Aristotle claimed, and it was certainly not the first "planet," a "eternal pearl to magnificently ascend into the heavenly empyrian," as Dante claimed. Galileo is sometimes credited with discovering the lunar libration in latitude in 1632, though it is possible that Thomas Harriot or William Gilbert did so first. Galileo's friend, the painter Cigoli, included a realistic depiction of the Moon in one of his paintings, though he most likely observed it with his own telescope. [1] [2] [3] [4] [5] [6] [7]

Jupiter And Its Moons

On January 7, 1610, Galileo used his telescope to observe "three fixed stars, totally invisible due to their smallness," all close to Jupiter and lying on a straight line through it. The observations the following nights revealed that the positions of these "stars" in relation to Jupiter were shifting in ways that would have been impossible to explain if they had been fixed stars. On January 10th, Galileo noticed that one of them had vanished, which he attributed to it being hidden behind Jupiter. After only a few days, he realized they were orbiting Jupiter: he had discovered three of Jupiter's four largest moons. He discovered the fourth on January 13th. Galileo named the Medicean stars after his future patron, Cosimo II de' Medici, Grand Duke of Tuscany, and Cosimo's three brothers. However, they were later renamed Galilean satellites after their discoverer. Galileo was appointed Grand Duke of Tuscany's mathematician and philosopher, and he triumphantly returned to his homeland in the fall of 1610. Galileo was now a courtier and lived the life of a gentleman. Galileo's observations of Jupiter's satellites sparked an astronomical revolution: a planet with smaller planets orbiting it contradicted Aristotelian cosmological principles, which stated that all heavenly bodies should revolve around the Earth, and many astronomers and philosophers initially refused to believe Galileo could have discovered such a thing. When he visited Rome in 1611, Christopher Clavius' observatory confirmed his observations, and he was greeted as a hero. The Collegio Romano held a grand dinner with speeches to honor Galileo's remarkable discoveries. Galileo was also chosen as the sixth member of the Accademia dei Lincei, an honor that meant a lot to him, and he began signing himself 'Galileo Galilei Linceo' from then on. Galileo continued to observe the satellites for the next eighteen months, and by mid-1611, he had obtained remarkably accurate estimates for their periods—a feat that Johannes Kepler had thought impossible. [1] [2] [3] [4] [5] [6] [7]

The Tides

Cardinal Bellarmine had written in 1615 that the Copernican system could not be defended without "a true physical demonstration that the sun does not circle the earth but the earth circles the sun". Galileo considered his theory of the tides to provide such evidence. This theory was so important to him that he originally intended to call his Dialogue Concerning the Two Chief World Systems the Dialogue on the Ebb and Flow of the Sea. The reference to tides was removed from the title by order of the Inquisition. For Galileo, the tides were caused by the sloshing back and forth of water in the seas as a point on the Earth's surface sped up and slowed down because of the Earth's rotation on its axis and revolution around the Sun. He circulated his first account of the tides in 1616, addressed to Cardinal Orsini. His theory gave the first insight into the importance of the shapes of ocean basins in the size and timing of tides; he correctly accounted, for instance, for the negligible tides halfway along the Adriatic Sea compared to those at the ends. As a general account of the cause of tides, however, his theory was a failure. If this theory were correct, there would be only one high tide per day. Galileo and his contemporaries were aware of this inadequacy because there are two daily high tides at Venice instead of one, about 12 hours apart. Galileo dismissed this anomaly as the result of several secondary causes including the shape of the sea, its depth, and other factors. Albert Einstein later expressed the opinion that Galileo developed his "fascinating arguments" and accepted them uncritically out of a desire for physical proof of the motion of the Earth. Galileo also dismissed the idea, known from antiquity and by his contemporary Johannes Kepler, that the Moon caused the tides—Galileo also took no interest in Kepler's elliptical orbits of the planets. Galileo continued to argue in favour of his theory of tides, considering it the ultimate proof of Earth's motion. [1] [2] [3] [4] [5] [6] [7]


  1. 1.0 1.1 1.2 1.3 Wikipedia Editors. “Galileo Galilei.” Wikipedia. Wikimedia Foundation, ( : 10 June 2021)
  2. 2.0 2.1 2.2 2.3 Van Helden, Albert. “Galileo.” Encyclopædia Britannica. Encyclopædia Britannica, inc. ( : 10 June 2021)
  3. 3.0 3.1 3.2 3.3 Boltz, C. L. “Galileo Galilei.” New Scientist. New Scientist, April 7, 1983. ( : 10 June 2021)
  4. 4.0 4.1 4.2 4.3 Editors. “Galileo Galilei.” A&E Television Networks, July 23, 2010. ( : 10 June 2021)
  5. 5.0 5.1 5.2 5.3 Redd, Nola Taylor. “Galileo Galilei: Biography, Inventions & Other Facts.” Space, November 14, 2017. ( : 20 June 2021)
  6. 6.0 6.1 6.2 6.3 Sheehan, William. “Happy 455th Birthday Galileo.”, February 15, 2019. ( : 20 June 2021)
  7. 7.0 7.1 7.2 7.3 O'Connor, J. J., and E. F. Robertson. “Galileo Galilei - Biography.” Maths History. Maths History, 2002. ( : 20 June 2021)

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