Galileo Galilei was a well-known physicist, mathematician, astronomer, and philosopher, from Italy. Read this biography, to know more about the childhood and profile of Galileo Galilei.

Galileo Galilei

Born on: February 15, 1564
Galileo Galilei
Born in: Pisa (then part of the Grand Duchy of Tuscany)
Nationality: Italian
Career: Physicist, Mathematician, Astronomer, Philosopher
Death: January 8, 1642
Galileo, known as the ‘Father of Modern Physics’ or ‘Father of Modern Science’, was an Italian physicist, mathematician, astronomer, and philosopher. He is one of the persons who played a major role in the scientific revolution. Amongst his most notable works till date are improvements to the telescope and the consequential astronomical observations. He discovered the four largest satellites of Jupiter and also observed and analyzed sunspots. Applied science and technology are the other areas in which Galileo worked. He supported Copernicanism and also proved the concept of heliocentrism.
Galileo was born on 15th February 1564 in Pisa, which then formed a part of the Grand Duchy of Tuscany. He was the eldest of the six children of Vincenzo Galilei, a famous lutenist and music theorist, and Giulia Ammannati. His family moved to Florence when he was hardly 8 years old. However, they did not take him along, rather left him with Jacopo Borghini, for two years. Galileo started studying at the Camaldolese Monastery, in Vallombrosa, around 21 miles to the southeast of Florence.
Early Life
After completing his schooling, Galileo enrolled for a medical degree at the University of Pisa, mainly on his father’s insistence. However, instead of completing his degree, he started studying mathematics. In 1589, he was appointed to the chair of mathematics in Pisa. Two years later, Galileo lost his father and was entrusted with the care of his younger brother, Michelagnolo. The following year, he moved to the University of Padua. There, he taught geometry, mechanics and astronomy, until 1610. It was during this time that he made major discoveries in both pure science and applied science.
Galileo fathered three children with Marina Gamba, out of wedlock. Of them, two were daughters - Virginia (1600) and Livia (1601), while the third one was a son - Vincenzio (1606). Since they were illegitimate, Galileo considered the girls unmarriageable. He sent both of them to convent of San Matteo in Arcetri, where they remained for the rest of their lives. Virginia became Maria Celeste and died on 2nd April 1634. She is buried with Galileo at the Basilica di Santa Croce di Firenze. Livia became Sister Arcangela and remained ill for the most of her life. However, Vincenzio was later legitimized and married Sestilia Bocchineri.
Later Life
Galileo published an account of his telescopic observations of the moons of Jupiter in 1610. He used these observations to support the concept of the sun-centered, Copernican theory of the universe. The following year, he went to Rome and demonstrated his telescope to the influential philosophers and mathematicians of the Jesuit Collegio Romano. He did this to prove his observation of the four moons of Jupiter. Galileo was also made a member of the Accademia dei Lincei, while he was in Rome. It was in 1612 that his concept of sun-centered solar system was opposed.
Two years later, in 1614, Father Tommaso Caccini criticized Galileo's opinions on the motion of the Earth, from the pulpit of Santa Maria Novella. He went a step further, to term them as dangerous and close to heterodoxy. In order to defend himself against these accusations, Rome decided to visit Rome. However, Cardinal Roberto Bellarmino met him in 1616 and personally handed him an admonition. It asked him to refrain from advocating or teaching the Copernican astronomy.
Last Years and Death
Galileo wrote his first book, The Assayer (Il Saggiatore), in 1621-1622. The book was approved and published in 1623. Seven years later, he came back to Rome and applied for a license to print the ‘Dialogue Concerning the Two Chief World Systems’. The book was published in Florence in 1632. The same year, in October, he was ordered to appear before the Holy Office in Rome. A papal trial followed, in the course of which, Galileo was found to be passionately suspected of sacrilege. As a result of the papal trial, he was placed under house arrest.
Along with that, the Pope also restricted his movements. In 1634, he moved to his country house at Arcetri, situated outside of Florence, where he remained till the end of his life. In 1638, Galileo lost his vision completely and also suffered from painful hernia and insomnia. In view of his deteriorating physical condition, he was permitted to travel to Florence, for medical advice. Galileo continued to receive visitors until 1642, the year in which he left for the holy abode, after suffering from fever and heart palpitations.
Scientific Methods
Galileo is credited with pioneering the use of quantitative experiments. The results of his experiments could be analyzed with mathematical accuracy. He is believed to be the first person who clearly stated that the laws of nature are mathematical. For his time, Galileo showed an amazingly modern appreciation of the proper relationship between mathematics, theoretical physics, & experimental physics. He comprehended the concept of parabola, in terms of both conic sections and the ordinate (y), varying as the square of abscissa (x).
During his time, Galileo claimed that parabola was the theoretically-ideal trajectory for uniformly accelerated motion, in the absence of friction and other disturbances. However, he also said that the theory will apply only in case of laboratory-scale and battlefield-scale trajectories. He admitted that it could not be applied to a trajectory the size of a planet. He also recognized that his experimental data would never agree exactly with any theoretical or mathematical form, owing to ambiguous measurement, irreducible friction, etc.
In 1608, Galileo, made a telescope with about 3x magnification. In the later years, he improved the telescope, to make one with up to about 32x magnification, which is now known as terrestrial telescope, or spyglass. His telescoep was used by merchants, for their shipping businesses and trading issues. In March 1610, he published a short treatise entitled Sidereus Nuncius (Starry Messenger), in which he provided his initial telescopic astronomical observations. The same year, he discovered the four moons of Jupiter, which he named as the ‘Medicean stars’.
Galileo later observed the phases of Venus and proved that it orbited the Sun. With this, he lent support to (but did not prove) the heliocentric model of Nicolaus Copernicus. Galileo was one of the first Europeans to observe and recognize sunspots. He also reinterpreted a sunspot observation from the time of Charlemagne. He reported lunar mountains and craters for the first time and also estimated the mountains' heights from observations about the patterns of light and shadow on the Moon's surface. Apart from that, he observed the Milky Way and a number of other, distant stars also.
  • Devised and improved a Geometric and Military Compass, suitable for use by gunners and surveyors
  • Constructed a thermometer
  • Used a refracting telescope as an instrument to observe stars, planets or moons
  • Made a compound microscope
  • Determined the orbital periods of Jupiter's satellites
  • Designed an escapement mechanism for a pendulum clock
  • Created sketches of various inventions, like a candle & mirror combination to reflect light throughout a building, an automatic tomato picker, a pocket comb that doubled as an eating utensil, a ballpoint pen, etc 
  • Performed rigorous experiments and used mathematical description of the laws of nature
  • Argued that the time of descent of objects, from a height, was independent of their mass
  • Arrived at the correct mathematical law for uniform acceleration that was already discovered by Domingo de Soto
  • Claimed (erroneously) that a pendulum's swings always take the same amount of time, independently of the amplitude
  • Described an experimental method to measure the speed of light
  • Presented a physical theory to account for tides, based on the motion of the Earth
  • Put forward the basic principle of relativity 
  • The Little Balance (1586)
  • The Starry Messenger (1610, in Latin)
  • Letters on Sunspots (1613)
  • Letter to the Grand Duchess Christina (1615, published in 1636)
  • Discourse on the Tides (1616, in Italian)
  • Discourse on the Comets (1619, in Italian)
  • The Assayer (1623, in Italian)
  • Dialogue Concerning the Two Chief World Systems (1632, in Italian)
  • Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638, in Italian) 
  • Galilean Moons (four large moons of Jupiter)
  • Galileo Spacecraft (first spacecraft to enter orbit around Jupiter)
  • Galileo Global Satellite Navigation System (Proposed)
  • Galilean Transformation (transformation between inertial systems in classical mechanics)
  • Gal (non-SI unit of acceleration)

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