94 Facts About Galileo

Galileo di Vincenzo Bonaiuti de' Galilei was an Italian astronomer, physicist and engineer, sometimes described as a polymath.

Galileo was born in the city of Pisa, then part of the Duchy of Florence.

Galileo has been called the "father" of observational astronomy, modern physics, the scientific method, and modern science.

Galileo studied speed and velocity, gravity and free fall, the principle of relativity, inertia, projectile motion and worked in applied science and technology, describing the properties of pendulums and "hydrostatic balances".

Galileo invented the thermoscope and various military compasses, and used the telescope for scientific observations of celestial objects.

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Galileo's championing of Copernican heliocentrism was met with opposition from within the Catholic Church and from some astronomers.

Galileo later defended his views in Dialogue Concerning the Two Chief World Systems, which appeared to attack Pope Urban VIII and thus alienated both the Pope and the Jesuits, who had both supported Galileo up until this point.

Galileo was tried by the Inquisition, found "vehemently suspect of heresy", and forced to recant.

Galileo became an accomplished lutenist himself and would have learned early from his father a scepticism for established authority.

When Galileo Galilei was eight, his family moved to Florence, but he was left under the care of Muzio Tedaldi for two years.

When Galileo was ten, he left Pisa to join his family in Florence and there he was under the tutelage of Jacopo Borghini.

Galileo Bonaiuti was buried in the same church, the Basilica of Santa Croce in Florence, where about 200 years later, Galileo Galilei was buried.

Galileo was influenced by the lectures of Girolamo Borro and Francesco Buonamici of Florence.

Up to this point, Galileo had deliberately been kept away from mathematics, since a physician earned a higher income than a mathematician.

Galileo created a thermoscope, a forerunner of the thermometer, and, in 1586, published a small book on the design of a hydrostatic balance he had invented .

Galileo studied disegno, a term encompassing fine art, and, in 1588, obtained the position of instructor in the Accademia delle Arti del Disegno in Florence, teaching perspective and chiaroscuro.

Galileo's multiple interests included the study of astrology, which at the time was a discipline tied to the studies of mathematics and astronomy.

Since these new stars displayed no detectable diurnal parallax, Galileo concluded that they were distant stars, and, therefore, disproved the Aristotelian belief in the immutability of the heavens.

Galileo later made improved versions with up to about 30x magnification.

Galileo's telescopes were a profitable sideline for Galileo, who sold them to merchants who found them useful both at sea and as items of trade.

Galileo is sometimes credited with the discovery of the lunar libration in latitude in 1632, although Thomas Harriot or William Gilbert might have done it before.

Galileo named the group of four the Medicean stars, in honour of his future patron, Cosimo II de' Medici, Grand Duke of Tuscany, and Cosimo's three brothers.

Galileo's observations were confirmed by the observatory of Christopher Clavius and he received a hero's welcome when he visited Rome in 1611.

Galileo continued to observe the satellites over the next eighteen months, and by mid-1611, he had obtained remarkably accurate estimates for their periods—a feat which Johannes Kepler had believed impossible.

In 1610, Galileo observed the planet Saturn, and at first mistook its rings for planets, thinking it was a three-bodied system.

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Galileo did not realise that it was a planet, but he did note its motion relative to the stars before losing track of it.

Galileo observed the Milky Way, previously believed to be nebulous, and found it to be a multitude of stars packed so densely that they appeared from Earth to be clouds.

Galileo located many other stars too distant to be visible with the naked eye.

Galileo observed the double star Mizar in Ursa Major in 1617.

Galileo devised a method for measuring the apparent size of a star without a telescope.

However, Galileo's values were much smaller than previous estimates of the apparent sizes of the brightest stars, such as those made by Brahe, and enabled Galileo to counter anti-Copernican arguments such as those made by Tycho that these stars would have to be absurdly large for their annual parallaxes to be undetectable.

Galileo considered his theory of the tides to provide such evidence.

Galileo circulated his first account of the tides in 1616, addressed to Cardinal Orsini.

Galileo's 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.

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 dismissed the idea, known from antiquity and by his contemporary Johannes Kepler, that the Moon caused the tides—Galileo 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.

In 1619, Galileo became embroiled in a controversy with Father Orazio Grassi, professor of mathematics at the Jesuit Collegio Romano.

Galileo defended heliocentrism based on his astronomical observations of 1609.

Two years later, Galileo wrote a letter to Christina that expanded his arguments previously made in eight pages to forty pages.

At the start of 1616, Monsignor Francesco Ingoli initiated a debate with Galileo, sending him an essay disputing the Copernican system.

Galileo later stated that he believed this essay to have been instrumental in the action against Copernicanism that followed.

The essay included four theological arguments, but Ingoli suggested Galileo focus on the physical and mathematical arguments, and he did not mention Galileo's biblical ideas.

Galileo revived his project of writing a book on the subject, encouraged by the election of Cardinal Maffeo Barberini as Pope Urban VIII in 1623.

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Galileo's resulting book, Dialogue Concerning the Two Chief World Systems, was published in 1632, with formal authorization from the Inquisition and papal permission.

Galileo was ordered to read the Seven Penitential Psalms once a week for the next three years.

Galileo went completely blind in 1638 and was suffering from a painful hernia and insomnia, so he was permitted to travel to Florence for medical advice.

Galileo was instead buried in a small room next to the novices' chapel at the end of a corridor from the southern transept of the basilica to the sacristy.

Galileo was reburied in the main body of the basilica in 1737 after a monument had been erected there in his honour; during this move, three fingers and a tooth were removed from his remains.

Galileo made original contributions to the science of motion through an innovative combination of experiment and mathematics.

Galileo was one of the first modern thinkers to clearly state that the laws of nature are mathematical.

Galileo's work marked another step towards the eventual separation of science from both philosophy and religion; a major development in human thought.

Galileo was often willing to change his views in accordance with observation.

Galileo showed a modern appreciation for the proper relationship between mathematics, theoretical physics, and experimental physics.

Galileo understood the parabola, both in terms of conic sections and in terms of the ordinate varying as the square of the abscissa .

Galileo further asserted that the parabola was the theoretically ideal trajectory of a uniformly accelerated projectile in the absence of air resistance or other disturbances.

Galileo conceded that there are limits to the validity of this theory, noting on theoretical grounds that a projectile trajectory of a size comparable to that of the Earth could not possibly be a parabola, but he nevertheless maintained that for distances up to the range of the artillery of his day, the deviation of a projectile's trajectory from a parabola would be only very slight.

Galileo made studies of sunspots, the Milky Way, and made various observations about stars, including how to measure their apparent size without a telescope.

Galileo made a number of contributions to what is known as engineering, as distinct from pure physics.

Between 1595 and 1598, Galileo devised and improved a geometric and military compass suitable for use by gunners and surveyors.

In 1593, Galileo constructed a thermometer, using the expansion and contraction of air in a bulb to move water in an attached tube.

In 1609, Galileo was, along with Englishman Thomas Harriot and others, among the first to use a refracting telescope as an instrument to observe stars, planets or moons.

In 1612, having determined the orbital periods of Jupiter's satellites, Galileo proposed that with sufficiently accurate knowledge of their orbits, one could use their positions as a universal clock, and this would make possible the determination of longitude.

Galileo worked on this problem from time to time during the remainder of his life, but the practical problems were severe.

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Late in his life, when totally blind, Galileo designed an escapement mechanism for a pendulum clock, although no clock using this was built until after the first fully operational pendulum clock was made by Christiaan Huygens in the 1650s.

Galileo was invited on several occasions to advise on engineering schemes to alleviate river flooding.

Galileo's theoretical and experimental work on the motions of bodies, along with the largely independent work of Kepler and Rene Descartes, was a precursor of the classical mechanics developed by Sir Isaac Newton.

Galileo claimed that a simple pendulum is isochronous, i e that its swings always take the same amount of time, independently of the amplitude.

Galileo found that the square of the period varies directly with the length of the pendulum.

Galileo is lesser known for, yet still credited with, being one of the first to understand sound frequency.

In 1638, Galileo described an experimental method to measure the speed of light by arranging that two observers, each having lanterns equipped with shutters, observe each other's lanterns at some distance.

Galileo reported that when he tried this at a distance of less than a mile, he was unable to determine whether or not the light appeared instantaneously.

Galileo put forward the basic principle of relativity, that the laws of physics are the same in any system that is moving at a constant speed in a straight line, regardless of its particular speed or direction.

Galileo proposed that a falling body would fall with a uniform acceleration, as long as the resistance of the medium through which it was falling remained negligible, or in the limiting case of its falling through a vacuum.

Galileo derived the correct kinematical law for the distance traveled during a uniform acceleration starting from rest—namely, that it is proportional to the square of the elapsed time .

Galileo did not, for instance, recognise, as Galileo did, that a body would fall with a strictly uniform acceleration only in a vacuum, and that it would otherwise eventually reach a uniform terminal velocity.

Galileo expressed the time-squared law using geometrical constructions and mathematically precise words, adhering to the standards of the day.

Galileo stated: "Imagine any particle projected along a horizontal plane without friction; then we know, from what has been more fully explained in the preceding pages, that this particle will move along this same plane with a motion which is uniform and perpetual, provided the plane has no limits".

Galileo's proposed solution, that infinite numbers cannot be compared, is no longer considered useful.

Galileo affair was largely forgotten after Galileo's death, and the controversy subsided.

The Inquisition's ban on reprinting Galileo's works was lifted in 1718 when permission was granted to publish an edition of his works in Florence.

Interest in the Galileo affair was revived in the early 19th century, when Protestant polemicists used it to attack Roman Catholicism.

Galileo was energetic on this point and regretted that in the case of Galileo.

On 31 October 1992, Pope John Paul II acknowledged that the Church had erred in condemning Galileo for asserting that the Earth revolves around the Sun.

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In March 2008, the head of the Pontifical Academy of Sciences, Nicola Cabibbo, announced a plan to honour Galileo by erecting a statue of him inside the Vatican walls.

Partly because the year 2009 was the fourth centenary of Galileo's first recorded astronomical observations with the telescope, the United Nations scheduled it to be the International Year of Astronomy.

Galileo is mentioned several times in the "opera" section of the Queen song, "Bohemian Rhapsody".

Galileo Galilei was recently selected as a main motif for a high-value collectors' coin: the €25 International Year of Astronomy commemorative coin, minted in 2009.

Galileo published a description of sunspots in 1613 entitled Letters on Sunspots suggesting the Sun and heavens are corruptible.

In 1615, Galileo prepared a manuscript known as the "Letter to the Grand Duchess Christina" which was not published in printed form until 1636.

In 1619, Mario Guiducci, a pupil of Galileo's, published a lecture written largely by Galileo under the title Discourse on the Comets, arguing against the Jesuit interpretation of comets.

In 1623, Galileo published The Assayer—Il Saggiatore, which attacked theories based on Aristotle's authority and promoted experimentation and the mathematical formulation of scientific ideas.

The value of Galileo's possessions were not realised, and duplicate copies were dispersed to other libraries, such as the Biblioteca Comunale degli Intronati, the public library in Sienna.