Galileo Galilei

Biography of Galileo Galilei
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Galileo Galilei Biography

Galileo Galilei was an Italian astronomer, physicist, mathematician, philosopher, and engineer, recognized for being one of the most emblematic and influential people in the history, of science. Galileo was born in Pisa, Italy on February 15, 1564, and was the son of Giulia Ammannati and Florentino Vincenzo Galilei.

In 1574, when his parents moved to Florence, he was in charge of a religious neighbor named Jacobo Borhini. The little one entered the convent of Santa María de Vallombrosa, where he received a pious formation which motivated him to join the religious life, but as his father was very skeptical he took advantage of Galileo who had an infection in his eye and took him out of the convent claiming lack of care.

Around 1581, Galileo entered the University of Pisa, where he enrolled as a medical student by his father’s will. Four years later, he would drop out of school without a degree, although with a good knowledge about Aristotle.

In 1585, he would return to Florence dedicating himself for several years to the study of mathematics. Galileo was also interested in philosophy and literature, in which he showed priority for Ariosto versus Tasso. That year, Galileo would release his first work on the barycenter of bodies and the creation of a hydrostatic balance for the determination of specific weights, two contributions located in the line of Archimedes, whom Galileo would not hesitate to describe as superhuman. He also began by demonstrating many theorems about the center of gravity of certain solids, continuing with his studies on the oscillations of the heavy pendulum and invented the heart rate monitor. This device allowed to help measure the pulse and provides a time scale, which did not exist at that time.

Three years later, in 1588, Galilei was invited by the Florentine Academy to present two lessons on “the shape, the place and the dimension of hell of Dante Alighieri”.

Simultaneous to his activities, he sought employment as a professor at a university and met great people, such as the Jesuit Father Christopher Clavius, a reference in mathematics at the Pontifical College, and with the mathematician Guidobaldo del Monte, who recommended Galileo to the duke Fernando I de Médici, so that he will hire Galileo for the chair of mathematics at the University of Pisa.

Between 1590 and 1591, Galileo Galilei discovered the Cycloid and used it to draw bridge arches. Also, he conducted experiments on the fall of the bodies and wrote his first work of mechanics, “De Motu Antiquiora”.

In 1592, he moved to the University of Padua and worked as a professor of geometry, mechanics, and astronomy until 1610. He also invented the compass of calculation which will help to solve basic problems of mathematics.

In 1599, he met Marina Gamba with whom he had a relationship until 1610, and with whom he had three children.

1604 was a successful one for Galileo since he managed to test his water pump in the garden of Padua, he also discovered the law of uniformly accelerated motion which he associated with a law of erroneous speeds, and he began his observations of a Nova.

Around 1605, he published: “Dialogue of Cecco di Ronchitti da Bruzene in Perpuosito de la Stella Nova” in collaboration with Girolamo Spinelli.

In 1606, Galileo Galilei built his first Thermoscope, the first device in history that made possible to objectively compare the level of heat and cold. That same year, he and two of his friends contracted an infectious disease of which only Galileo survived, which is why he remained crippled with rheumatism for the rest of his life. In the next two years, he studied the structures of magnets.

Throughout 1609, he received a letter from the Frenchman Jacques Badovere, one of his former students, confirming an insistent rumor: the existence of a telescope that allowed to see distant objects, this telescope would have already allowed seeing stars invisible to simple view. With this unique description, Galileo built his first telescope. A unique object at that time that was able to obtain a right image thanks to the use of a diverging lens in the eyepiece, this invention takes an important turn in his life.

Galileo Galilei continued developing his telescope and would make an instrument that increases the image twenty times, placed it to the sky observing the phases of the Moon with mountains and craters. Galileo managed to discover the four largest satellites of Jupiter, and later published his book “The Starry Messenger”.

On January 7, 1610, Galileo made a capital discovery: he perceived three small stars on the periphery of Jupiter. But after observing for many nights, he discovered that there are four of them and that they will spin around the planet.

On March 4 of 1610, he published in Florence his discoveries in “The Starry Messenger”. On July 25, he also oriented his telescope to Saturn discovering its strange appearance, then found a way to observe the Sun in the telescope and discovered sunspots. Galileo Galilei continued to discover things, and two months later, he discovered the phases of Venus, what was for him, a new proof of the truth of the system of Nicolaus Copernicus. On March 29, 1611, he was invited by Cardinal Maffeo Barberini to present his discoveries to the Pontifical College of Rome and the Academy of the Lynxes. Galileo remained in the pontifical capital for a full month, during which he received all the honors.

Galileo’s observations were examined by the Roman College and confirmed to Cardinal Robert Bellarmine that those were accurate.  Galileo Galilei would return to Florence to continue with his investigations. In the month of March of 1628, Galileo Galilei became seriously ill. However, he managed to recover after a while, to continue with his work.

On February 21, 1632, he published his dialogue of the “Massimi Sistemi” in Florence. By the year 1633, Galileo Galilei was sentenced to life imprisonment with house arrest. Also, the sentence stated that all copies of some of his books should be burned and the sentence against him should be read publicly in all universities.

His last book was published in 1638, in which he discussed and improved his early studies in the movement and the principles of physics. This book would be used by Isaac Newton later on.

Galileo lost his sight before his last book was published and would die on January 8, 1642, in Arcetri, Italy, at the age of 77 years. His body was buried in Florence on January 9.


published written work

  • 1586: La Bilancetta (posthumous publication).
  • 1590: De Motu Antiquiora.
  • 1606: Le Operazioni del compasso geometrico et militare.
  • 1600: Le meccaniche.
  • 1610: Mensajero Sideral, Siderus nuncius.
  • 1616: Discorso del flusso e reflusso del mare.
  • 1619: Discorso delle comete (publicado por Mario Guiducci).
  • 1623: Il. Saggiatore.
  • 1632: Massimi Sistemi
  • 1638: Discorsi e dimostrazioni matematiche, intorno a due nuove scienze attenenti alla meccanica & i movimenti locali.
  • The Assayer (José Manuel Revuelta, trad. y ed.), Aguilar, Buenos Aires: 1984.


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