Galileo started his formal education in the monastery of Vallombrosa (Vallombrosa Abbey), graduating from it in 1578.
College/University
Gallery of Galileo Galilei
Lungarno Antonio Pacinotti, 43, 56126 Pisa PI, Italy
Galileo entered the University of Pisa for a medical degree in 1850, however, he left the university in 1585, after he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession.
Galileo then also taught at the University of Pisa from 1589 to 1592.
Career
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Gallery of Galileo Galilei
Achievements
The International Year of Astronomy collector's coin features a picture of Galileo. This coin also commemorates the 400th anniversary of the invention of Galileo's telescope. The obverse shows a portion of his portrait and his telescope. The background shows one of his first drawings of the surface of the moon.
The International Year of Astronomy collector's coin features a picture of Galileo. This coin also commemorates the 400th anniversary of the invention of Galileo's telescope. The obverse shows a portion of his portrait and his telescope. The background shows one of his first drawings of the surface of the moon.
Lungarno Antonio Pacinotti, 43, 56126 Pisa PI, Italy
Galileo entered the University of Pisa for a medical degree in 1850, however, he left the university in 1585, after he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession.
Galileo then also taught at the University of Pisa from 1589 to 1592.
(Galileo Galilei’s Sidereus Nuncius is arguably the most d...)
Galileo Galilei’s Sidereus Nuncius is arguably the most dramatic scientific book ever published. It announced new and unexpected phenomena in the heavens, "unheard of through the ages," revealed by a mysterious new instrument. Galileo had ingeniously improved the rudimentary "spyglasses" that appeared in Europe in 1608, and in the autumn of 1609 he pointed his new instrument at the sky, revealing astonishing sights: mountains on the moon, fixed stars invisible to the naked eye, individual stars in the Milky Way, and four moons around the planet Jupiter.
Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican
(Galileo’s Dialogue Concerning the Two Chief World Systems...)
Galileo’s Dialogue Concerning the Two Chief World Systems, published in Florence in 1632, was the most proximate cause of his being brought to trial before the Inquisition. Using the dialogue form, a genre common in classical philosophical works, Galileo masterfully demonstrates the truth of the Copernican system over the Ptolemaic one, proving, for the first time, that the earth revolves around the sun. Its influence is incalculable. The Dialogue is not only one of the most important scientific treatises ever written, but a work of supreme clarity and accessibility, remaining as readable now as when it was first published.
(Galileo's final book, the culmination of a life of scient...)
Galileo's final book, the culmination of a life of scientific and mathematical work. It includes observations about the motion of objects and gravity which formed the foundation for Newton's Laws of Motion.
(This is the standard translation of one of the greatest s...)
This is the standard translation of one of the greatest single works by one of the Western sciences' greatest single men, the Renaissance physicist Galileo Galilei. Written near the end of his life, the book had to be published abroad and led to Galileo's condemnation. But he nevertheless considered it to be "superior to everything else of mine published."
Galileo Galilei was an Italian polymath: astronomer, physicist, engineer, philosopher, and mathematician. He has been called "the father of observational astronomy," "the father of modern physics," "the father of the scientific method," and "the father of science." His experiments convincingly refuted Aristotle's speculative metaphysics and laid the foundation of classical mechanics.
Background
Galileo Galilei was born on 15 February 1564, in Pisa, Italy, the first of six children of Vincenzo Galilei and Giulia (née Ammannati), who had married in 1562. However, only three of Galileo's five siblings survived infancy.
From his earliest childhood, Galileo was remarkable for intellectual aptitude as well as for mechanical invention. His favorite pastime was the construction of original and ingenious toy-machines, but his application to literary studies was equally conspicuous.
The youngest, Michelangelo (or Michelagnolo), also became a noted lutenist and composer although he contributed to financial burdens during Galileo's young adulthood. Michelangelo was unable to contribute his fair share of their father's promised dowries to their brothers-in-law, who would later attempt to seek legal remedies for payments due. Michelangelo would also occasionally have to borrow funds from Galileo to support his musical endeavours and excursions. These financial burdens may have contributed to Galileo's early desire to develop inventions that would bring him additional income.
When Galileo Galilei was eight, his family moved to Florence, but he was left with Jacopo Borghini for two years.
Education
Galileo started his formal education in the monastery of Vallombrosa (Vallombrosa Abbey). As a young man, Galileo was torn between training to become a Catholic priest or a doctor of medicine. His father encouraged him to study medicine, and Galileo took his father’s advice, starting a medical course at the University of Pisa when he was 17 years old. However, he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father. In 1585, Galileo left the University of Pisa without having obtained a degree. His zeal astonished Ostilio Ricci, a family friend and professor at the Academy of Design, so Galileo also started studying design and did it till 1588.
In 1611, Galileo Galilei was awarded an honorary degree by the Jesuit College in Rome.
After leaving the university, Galileo gave private lessons in the mathematical subjects in Florence and Siena for several years. During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta (“The Little Balance”), that circulated in manuscript form and first brought him to the attention of the scholarly world. He also began his studies on motion, which he pursued steadily for the next two decades.
In 1588 Galileo applied for the chair of mathematics at the University of Bologna but was unsuccessful. His reputation was, however, increasing, and later that year he was asked to deliver two lectures to the Florentine Academy, a prestigious literary group, on the arrangement of the world in Dante’s Inferno. He also found some ingenious theorems on centres of gravity that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte, a nobleman and author of several important works on mechanics. As a result, he obtained the chair of mathematics at the University of Pisa in 1589. There, according to his first biographer, Vincenzo Viviani, Galileo demonstrated, by dropping bodies of different weights from the top of the famous Leaning Tower, that the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. The manuscript tract De motu (On Motion), finished during this period, shows that Galileo was abandoning Aristotelian notions about motion and was instead taking an Archimedean approach to the problem. But his attacks on Aristotle made him unpopular with his colleagues, and in 1592 his contract was not renewed. His patrons, however, secured him the chair of mathematics at the University of Padua, where he taught from 1592 until 1610. The 18 years he spent there and, according to his own admission, those were the happiest years of his life.
Although Galileo’s salary was considerably higher there, his responsibilities as the head of the family (his father had died in 1591) meant that he was chronically pressed for money. His university salary could not cover all his expenses, and he, therefore, took in well-to-do boarding students whom he tutored privately in such subjects as fortification. He also sold a proportional compass, or sector, of his own devising, made by an artisan whom he employed in his house. In the midst of his busy life, he continued his research on motion, and by 1609 he had determined that the distance fallen by a body is proportional to the square of the elapsed time (the law of falling bodies) and that the trajectory of a projectile is a parabola, both conclusions that contradicted Aristotelian physics.
At this point, however, Galileo’s career took a dramatic turn. In the spring of 1609, he heard that in the Netherlands the instrument that showed distant things as though they were nearby had been invented. By trial and error, he quickly figured out the secret of the invention and made his own three-powered spyglass from lenses for sale in spectacle makers’ shops. Others had done the same; what set Galileo apart was that he quickly figured out how to improve the instrument, taught himself the art of lens grinding, and produced increasingly powerful telescopes.
In August of that year, he presented an eight-powered instrument to the Venetian Senate (Padua was in the Venetian Republic). He was rewarded with life tenure and a doubling of his salary. Galileo was now one of the highest-paid professors at the university. In the fall of 1609, Galileo began observing the heavens with instruments that magnified up to 20 times.
It was also the intuitive stroke of a genius that made him turn the telescope toward the sky sometime in the fall of 1609, a feat which a dozen other people could very well have done during the previous 4 to 5 years. Within a few months, he gathered astonishing evidence about mountains on the moon, about moons circling Jupiter, and about an incredibly large number of stars, especially in the belt of the Milky Way. On March 12, 1610, all these sensational items were printed in Venice under the title Sidereus Nuncius (The Starry Messenger), a booklet which took the world of science by storm.
In December of that year, Galileo drew the Moon’s phases as seen through the telescope, showing that the Moon’s surface is not smooth, as had been thought, but is rough and uneven. In January 1610, he discovered four moons revolving around Jupiter. He also found that the telescope showed many more stars that are visible with the naked eye. These discoveries were earthshaking, which he described in his book The Starry Messenger. He dedicated the book to Cosimo II de Medici, the grand duke of his native Tuscany, whom he had tutored in mathematics for several summers, and he named the moons of Jupiter after the Medici family: the Sidera Medicea or "Medicean Stars." Galileo was rewarded with an appointment as mathematician and philosopher of the grand duke of Tuscany, and in the fall of 1610, he returned in triumph to his native land.
Galileo was now a courtier and lived the life of a gentleman. Before he left Padua, he had discovered the puzzling appearance of Saturn, later to be shown as caused by a ring surrounding it, and in Florence, he discovered that Venus goes through phases just as the Moon does. Although these discoveries did not prove that Earth is a planet orbiting the Sun, they undermined Aristotelian cosmology: the absolute difference between the corrupt earthly region and the perfect and unchanging heavens was proved wrong by the mountainous surface of the Moon, the moons of Jupiter showed that there had to be more than one centre of motion in the universe, and the phases of Venus showed that it (and, by implication, Mercury) revolves around the Sun. As a result, Galileo was confirmed in his belief, which he had probably held for decades but which had not been central to his studies, that the Sun is the center of the universe and that Earth is a planet, as Copernicus had argued. Thus, Galileo’s conversion to Copernicanism would be a key turning point in the scientific revolution.
Galileo's move to Florence turned out to be highly unwise, as events soon showed. In the beginning, however, everything was pure bliss. He made a triumphal visit to Rome in 1611. The next year saw the publication of his Discourse on Bodies in Water. There he disclosed his discovery of the phases of Venus (a most important proof of the truth of the Copernican theory), but the work was also the source of heated controversies.
After a brief controversy about floating bodies, Galileo again turned his attention to the heavens and entered a debate with Christoph Scheiner, a German Jesuit and professor of mathematics at Ingolstadt, about the nature of sunspots (of which Galileo was an independent discoverer). This controversy resulted in Galileo’s Istoria e dimostrazioni intorno alle macchie solari e loro accidenti ("History and Demonstrations Concerning Sunspots and Their Properties," or "Letters on Sunspots"), which appeared in 1613. Against Scheiner, who, in an effort to save the perfection of the Sun, argued that sunspots are satellites of the Sun, Galileo argued that the spots are on or near the Sun’s surface, and he bolstered his argument with a series of detailed engravings of his observations.
Galileo’s increasingly overt Copernicanism began to cause trouble for him. In 1613, he wrote a letter to his student Benedetto Castelli in Pisa about the problem of squaring the Copernican theory with certain biblical passages. Inaccurate copies of this letter were sent by Galileo’s enemies to the Inquisition in Rome, and he had to retrieve the letter and send an accurate copy. Several Dominican fathers in Florence lodged complaints against Galileo in Rome, and Galileo went to Rome to defend the Copernican cause and his good name. Before leaving, he finished an expanded version of the letter to Castelli, now addressed to the grand duke’s mother and good friend of Galileo, the dowager Christina. In his Letter to the Grand Duchess Christina, Galileo discussed the problem of interpreting biblical passages with regard to scientific discoveries but, except for one example, did not actually interpret the Bible. That task had been reserved for approved theologians in the wake of the Council of Trent and the beginning of the Catholic Counter-Reformation. But the tide in Rome was turning against the Copernican theory, and in 1615, when the cleric Paolo Antonio Foscarini published a book arguing that the Copernican theory did not conflict with scripture, Inquisition consultants examined the question and pronounced the Copernican theory heretical. Foscarini’s book was banned, as were some more technical and nontheological works, such as Johannes Kepler’s Epitome of Copernican Astronomy. Copernicus’s own 1543 book, De revolutionibus orbium coelestium libri vi (“Six Books Concerning the Revolutions of the Heavenly Orbs”), was suspended until corrected. Galileo was not mentioned directly in the decree, but he was admonished by Robert Cardinal Bellarmine not to “hold or defend” the Copernican theory.
Galileo also drew a distinction between the properties of external objects and the sensations they cause in us - i. e., the distinction between primary and secondary qualities. Publication of Il saggiatore came at an auspicious moment, for Maffeo Cardinal Barberini, a friend, admirer, and patron of Galileo for a decade was named Pope Urban VIII as the book was going to press. Galileo’s friends quickly arranged to have it dedicated to the new pope. In 1624, Galileo went to Rome and had six interviews with Urban VIII. Galileo told the pope about his theory of the tides (developed earlier), which he put forward as proof of the annual and diurnal motions of Earth. The pope gave Galileo permission to write a book about theories of the universe but warned him to treat the Copernican theory only hypothetically. The book, Dialogo sopra i due massimi sistemi del mondo (“Dialogue Concerning the Two Chief World Systems, Ptolemaic & Copernican”), was finished in 1630, and Galileo sent it to the Roman censor. Because of an outbreak of the plague, communications between Florence and Rome were interrupted, and Galileo asked for the censoring to be done instead in Florence. The Roman censor had a number of serious criticisms of the book and also forwarded these to his colleagues in Florence. After writing a preface in which he professed that what followed was written hypothetically, Galileo had little trouble getting the book through the Florentine censors, and it appeared in Florence in 1632.
In the Dialogue’s witty conversation between Salviati (representing Galileo), Sagredo (the intelligent layman), and Simplicio (the dyed-in-the-wool Aristotelian), Galileo gathered together all the arguments (mostly based on his own telescopic discoveries) for the Copernican theory and against the traditional geocentric cosmology. As opposed to Aristotle’s, Galileo’s approach to cosmology is fundamentally spatial and geometric: Earth’s axis retains its orientation in space as Earth circles the Sun, and bodies not under a force retain their velocity (although this inertia is ultimately circular). But in giving Simplicio the final word, that God could have made the universe any way he wanted to and still made it appear to us the way it does, he put Pope Urban VIII’s favorite argument in the mouth of the person who had been ridiculed throughout the dialogue. The reaction against the book was swift. The pope convened a special commission to examine the book and make recommendations; the commission found that Galileo had not really treated the Copernican theory hypothetically and recommended that a case was brought against him by the Inquisition.
Galileo was summoned to Rome in 1633. During his first appearance before the Inquisition, he was confronted with the 1616 edict recording that he was forbidden to discuss the Copernican theory. In his defense Galileo produced a letter from Cardinal Bellarmine, by then dead, stating that he was admonished only not to hold or defend the theory. The case was at somewhat of an impasse, and, in what can only be called a plea bargain, Galileo confessed to having overstated his case. He was pronounced to be vehemently suspect of heresy and was condemned to life imprisonment and was made to abjure formally. It should be noted that Galileo was never in a dungeon or tortured; during the Inquisition process he stayed mostly at the house of the Tuscan ambassador to the Vatican and for a short time in a comfortable apartment in the Inquisition building.
After the process, Galileo spent six months at the palace of Ascanio Piccolomini, the archbishop of Siena and a friend and patron, and then moved into a villa near Arcetri, in the hills above Florence. He spent the rest of his life there. Galileo’s daughter Sister Maria Celeste, who was in a nearby nunnery, was a great comfort to her father until her untimely death in 1634.
Galileo was then 70 years old. Yet he kept working. In Siena, he had begun a new book on the sciences of motion and strength of materials. There he wrote up his unpublished studies that had been interrupted by his interest in the telescope in 1609 and pursued intermittently since. The book was spirited out of Italy and published in Leiden, the Netherlands, in 1638 under the title Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alla meccanica ("Dialogues Concerning Two New Sciences"). Galileo here treated for the first time the bending and breaking of beams and summarized his mathematical and experimental investigations of motion, including the law of falling bodies and the parabolic path of projectiles as a result of the mixing of two motions, constant speed, and uniform acceleration. By then Galileo had become blind, and he spent his time working with a young student, Vincenzo Viviani, who was with him when he died on January 8, 1642.
The Grand Duke of Tuscany, Ferdinando II, wished to bury him in the main body of the Basilica of Santa Croce, next to the tombs of his father and other ancestors, and to erect a marble mausoleum in his honor. These plans were dropped, however, after Pope Urban VIII and his nephew, Cardinal Francesco Barberini, protested because Galileo had been condemned by the Catholic Church for "vehement suspicion of heresy." He 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. He was reburied in the main body of the basilica in 1737 after a monument had been erected there in his honor; during this move, three fingers and a tooth were removed from his remains.
The Italian scientist Galileo Galilei was an astronomer and scientist who launched the scientific revolution and is widely considered the father of modern science. He is renowned for his epoch-making contributions to astronomy, physics, and scientific philosophy. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and the universe around him. He was a prolific inventor who is credited with several inventions including a hydrostatic balance, a military compass and a forerunner of the modern thermometer.
Galileo was also the first known person who studied the skies in detail with a telescope. He made numerous significant discoveries in astronomy including the Phases of Venus and the four largest moons of Jupiter. His contributions to science include the Galilean Invariance and the discovery of Isochronism in pendulums.
Among major works of Galileo Galilei one can name The Little Balance (1586), On Motion (1590), Mechanics (1600), The Starry Messenger (1610), Discourse on Floating Bodies (1612), Discourse on the Tides (1616), The Assayer (1623), Dialogue Concerning the Two Chief World Systems (1632), Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638).
A number of things have been named after Galilei including the Galilean moons of Jupiter, the Galileo spacecraft, Asteroid 697 Galilea, the proposed Galileo global satellite navigation system as well as Galilean transformation, the change between inertial systems in classical mechanics. In addition, the International Year of Astronomy collector's coin features a picture of him. This coin also commemorates the 400th anniversary of the invention of Galileo's telescope. The obverse shows a portion of his portrait and his telescope. The background shows one of his first drawings of the surface of the moon.
Galileo was also mentioned in the media. He was mentioned several times in the "opera" section of the Queen song, "Bohemian Rhapsody". He features prominently in the song "Galileo" performed by the Indigo Girls and Amy Grant's Galileo on her Heart in Motion album.
Several plays have been written on Galileo's life, including Life of Galileo (1943) by the German playwright Bertolt Brecht, with a film adaptation (1975) of it, and Lamp At Midnight (1947) by Barrie Stavis, as well as the 2008 play "Galileo Galilei".
Kim Stanley Robinson wrote a science fiction novel entitled Galileo's Dream (2009).
In 2009, the Galileoscope was also released. This is a mass-produced, low-cost educational 2-inch (51 mm) telescope with relatively high quality.
It was in Rome in 1633 that Galileo was forced to stand trial and found "vehemently suspect of heresy," mainly for his support of the heliocentric view of the universe. By publicly renouncing his opinion, Galileo managed to avoid the death penalty but was forced to spend the rest of his life under house arrest. Despite all of this, by official accounts, Galileo remained a committed Catholic right through to his death in 1642.
Whilst Catholics often refer to Galileo’s unerring faith, many atheists point out that it was very difficult to be anything but Catholic in 17th Century Italy. Their basic argument is that had Galileo not feared for his life, then he would more than likely have been an atheist. According to dominant atheist culture, Galileo pretended to be a believer but he was really a convinced atheist. Galileo was convinced that Divine Providence could not miss nor disregard anything to do with the government of human affairs.
Views
As the main focus underlying Galileo’s accomplishments, it is useful to see him as being interested in finding a unified theory of matter, a mathematical theory of the material stuff that constitutes the whole of the cosmos. Perhaps he didn’t realize that this was his grand goal until the time he actually wrote the Discourses on the Two New Sciences in 1638. Despite working on problems of the nature of matter from 1590 onwards, he could not have written his final work much earlier than 1638, certainly not before The Starry Messenger of 1610, and actually not before the Dialogues on the Two Chief World Systems of 1632. Before 1632, he did not have the theory and evidence he needed to support his claim about the unified, singular matter. He had thought deeply about the nature of matter before 1610 and had tried to work out how best to describe matter, but the idea of unified matter theory had to wait on the establishment of principles of matter’s motion on a moving earth. And this he did not do until the Dialogues.
Galileo began his critique of Aristotle in the 1590 manuscript, De Motu. The first part of this manuscript deals with terrestrial matter and argues that Aristotle’s theory has it wrong. For Aristotle, sublunary or terrestrial matter is of four kinds (earth, air, water, and fire) and has two forms, heavy and light, which by nature are different principles of motion, down and up. Galileo, using an Archimedian model of floating bodies and later the balance, argues that there is only one principle of motion, the heavy (gravitas), and that lightness (or levitas) is to be explained by the heavy bodies moving so as to displace or extrude other bits of matter in such a direction that explains why the other bits rise. So on his view heaviness (or gravity) is the cause of all natural terrestrial motion. But this left him with a problem as to the nature of the heavy, the nature of gravitas? In De Motu, he argued that the moving arms of a balance could be used as a model for treating all problems of motion. In this model heaviness is the proportionality of weight of one object on one arm of a balance to that of the weight of another body on the other arm of the balance. In the context of floating bodies, weight is the ‘weight’ of one body minus weight of the medium.
Galileo realized quickly these characterizations were insufficient, and so began to explore how heaviness was relative to the different specific gravities of bodies having the same volume. He was trying to figure out what is the concept of heaviness that is characteristic of all matter. What he failed to work out, and this was probably the reason why he never published De Motu, was this positive characterization of heaviness. There seemed to be no way to find standard measures of heaviness that would work across different substances. So at this point he did not have useful replacement categories.
In 1603–1609, Galileo worked long at doing experiments on inclined planes and most importantly with pendula. The pendulum again exhibited to Galileo that acceleration and, therefore, time is a crucial variable. Moreover, isochrony
- equal times for equal lengths of string, despite different weights - goes someway towards showing that time is a possible form for describing the equilibrium (or ratio) that needs to be made explicit in representing motion. It also shows that in at least one case time can displace weight as a crucial variable.
Galileo’s law of free fall arises out of this struggle to find the proper categories for his new science of matter and motion. Galileo accepts, probably as early as the 1594 draft of Le Mecaniche, that natural motions might be accelerated. But that accelerated motion is properly measured against time is an idea enabled only later, chiefly through his failure to find any satisfactory dependence on place and specific gravity. Galileo must have observed that the speeds of bodies increase as they move downwards and, perhaps, do so naturally, particularly in the cases of the pendulum, the inclined plane, in free fall, and during projectile motion. Also at this time he begins to think about percussive force, the force that a body acquires during its motion that shows upon impact. For many years he thinks that the correct science of these changes should describe how bodies change according to where they are on their paths. Specifically, it seems that height is crucial. Percussive force is related to height and the motion of the pendulum seems to involve essentially equilibrium with respect to the height of the bob.
The law of free fall, expressed as time squared, was discovered by Galileo through the inclined plane experiments, but he attempted to find an explanation of this relation, and the equivalent means proportional relation, through a velocity-distance relation. His later and correct definition of natural acceleration as dependent on time is an insight gained through recognizing the physical significance of the mean proportional relation. Yet Galileo would not publish anything making time central to motion until 1638, in Discourses on the Two New Sciences. But let us return to the main matter.
In 1609 Galileo begins his work with the telescope. Many interpreters have taken this to be an interlude irrelevant to his physics. The Starry Messenger, which describes his early telescopic discoveries, was published in 1610. There are many ways to describe Galileo’s findings but for present purposes they are remarkable as his start at dismantling of the celestial/terrestrial distinction. Perhaps the most unequivocal case of this is when he analogizes the mountains on the moon to mountains in Bohemia. The abandonment of the heaven/earth dichotomy implied that all matter is of the same kind, whether celestial or terrestrial. Further, if there is only one kind of matter there can be only one kind of natural motion, one kind of motion that this matter has by nature. So it has to be that one law of motion will hold for earth, fire, and the heavens. This is a far stronger claim than he had made back in 1590. In addition, he described his discovery of the four moons circling Jupiter, which he called politically the Medicean stars (after the ruling family in Florence, his patrons). In the Copernican system, the earth having a moon revolve around it was unique and so seemingly problematic. Jupiter’s having planets made the earth-moon system non-unique and so again the earth became like the other planets. Some fascinating background and treatments of this period of Galileo’s life and motivations have recently appeared.
A few years later in his Letters on the Sunspots (1612), Galileo enumerated more reasons for the breakdown of the celestial/terrestrial distinction. Basically the ideas here were that the sun has spots (maculae) and rotated in a circular motion, and, most importantly Venus had phases just like the moon, which was the spatial key to physically locating Venus as being between the Sun and the earth, and as revolving around the Sun. In these letters he claimed that the new telescopic evidence supported the Copernican theory. Certainly the phases of Venus contradicted the Ptolemaic ordering of the planets.
Later in 1623, Galileo argued for a quite mistaken material thesis. In The Assayer, he tried to show that comets were sublunary phenomena and that their properties could be explained by optical refraction. While this work stands as a masterpiece of scientific rhetoric, it is somewhat strange that Galileo should have argued against the super-lunary nature of comets, which the great Danish astronomer Tycho Brahe had demonstrated earlier.
Galileo differed dramatically from Ptolemy, Copernicus, or even Tycho Brahe, who had demolished the crystalline spheres by his comets-as-celestial argument and flirted with physical models. So on the new Galilean scheme there is only one kind of matter, and it may have only one kind of motion natural to it. Therefore, he had to devise principles of local motion that will fit a central sun, planets moving around that sun, and a daily whirling earth.
In Day One of his Dialogues on the Two Chief World Systems (1632), Galileo argued that all natural motion is circular. Then, in Day Two, he introduced his version of the famous principle of the relativity of observed motion. This latter held that motions in common among bodies could not be observed. Only those motions differing from a shared common motion could be seen as moving. The joint effect of these two principles was to say that all matter shares a common motion, circular, and so only motions different from the common, say up and down motion, could be directly observed.
In Day Three, Galileo dramatically argues for the Copernican system. Salviati, the persona of Galileo, has Simplicio, the ever astounded Aristotelian, make use of astronomical observations, especially the facts that Venus has phases and that Venus and Mercury are never far from the Sun, to construct a diagram of the planetary positions. The resulting diagram neatly corresponds to the Copernican model. Earlier in Day One, he had repeated his claims from The Starry Messenger, noting that the earth must be like the moon in being spherical, dense and solid, and having rugged mountains. Clearly the moon could not be a crystalline sphere as held by some Aristotelians.
It is in this way that Galileo developed the new categories of the mechanical new science, the science of matter and motion. His new categories utilized some of the basic principles of traditional mechanics, to which he added the category of time and so emphasized acceleration. But throughout, he was working out the details about the nature of matter so that it could be understood as uniform and treated in a way that allowed for coherent discussion of the principles of motion.
Quotations:
"You cannot teach a man anything; you can only help him find it within himself."
"Measure what is measurable, and make measurable what is not so."
"All truths are easy to understand once they are discovered; the point is to discover them."
"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use."
"Wine is sunlight, held together by water."
"In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual."
"I have never met a man so ignorant that I couldn't learn something from him."
"Mathematics is the language with which God has written the universe."
"The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do."
"The Bible shows the way to go to heaven, not the way the heavens go."
Membership
Accademia dei Lincei
,
Italy
1611
Personality
Although Galileo was quite smart and had a thoughtful mind, he was likely anything but shy. He was bold enough to publicly speak his belief in heliocentrism over geocentrism, and it’s likely that he actively defied the Church doctrine even after he was put under a census. Basically, he was definitely an intelligent and thoughtful man, but he was most likely also stubborn, arrogant, and vocal in his beliefs.
Physical Characteristics:
Galileo Galilei was mid-tall of 5.6 foot tall. He was chubby and always had a beard. He always dressed formal and he was very hygienic.
Quotes from others about the person
"Galileo's recognition of the cardinal property of all infinite classes makes him one of the genuine anticipators in the history of calculus. The other was Archimedes." - Eric Temple Bell
"The credit of first using the telescope for astronomical purposes is almost invariably attributed to Galilei, though his first observations were in all probability slightly later in date than those of Harriot and Marius, is to a great extent justified by the persistent way in which he examined object after object, whenever there seemed any reasonable prospect of results following, by the energy and acuteness with which he followed up each clue, by the independence of mind with which he interpreted his observations, and above all by the insight with which he realized their astronomical importance." - Arthur Berry
"His brilliant discoveries the man of science regards as his peculiar property; the means by which they were made, and the development of his intellectual character, belong to the logician and to the philosopher; but the triumphs and the reverses of his eventful life must be claimed for our common nature, as a source of more than ordinary instruction." - David Brewster
"Others before him had asked why heavy bodies fall; now, the homogeneity of the earth with the heavenly bodies having suggested that terrestrial motion is a proper subject for exact mathematical study, we have the further question raised: how do they fall? with the expectation that the answer will be given in mathematical terms." - Edwin Arthur Burtt
"While Stevin investigated statics, Galileo pursued principally dynamics. Galileo was the first to abandon the Aristotelian idea that bodies descend more quickly in proportion as they are heavier; he established the first law of motion; determined the laws of falling bodies; and, having obtained a clear notion of acceleration and of the independence of different motions, was able to prove that projectiles move in parabolic curves. Up to his time it was believed that a cannon-ball moved forward at first in a straight line and then suddenly fell vertically to the ground. Galileo had an understanding of centrifugal forces, and gave a correct definition of momentum. Though he formulated the fundamental principles of statics, known as the parallelogram of forces, yet he did not fully recognize its scope. The principle of virtual velocities was partly conceived by Guido Ubaldo (died 1607), and afterwards more fully by Galileo." - Florian Cajori
"It is impossible to exaggerate the effects of his telescopic discoveries on Galileo's life, so profound were they. Not only is it true of Galileo's personal life and thought, but it equally true of their influence on the history of scientific thought. Galileo had the experience of beholding the heavens as they actually are for perhaps the first time, and wherever he looked he found evidence to support the Copernican system against the Ptolemaic, or at least weaken the authority of the ancients. This shattering experience - of observing the depths of the universe, of being the first mortal to know what the heavens are actually like - made so deep a an impression... that it is only by considering the events of 1609... that one can understand the subsequent direction of his life." - I. Bernard Cohen
"Galileo was no idiot. Only an idiot could believe that science requires martyrdom - that may be necessary in religion, but in time a scientific result will establish itself." - David Hilbert
"The beginning of astronomy, except observations, I think is not to be derived from farther time than from Nicolaus Copernicus; who in the age next preceding the present revived the opinion of Pythagoras, Aristarchus, and Philolaus. After him, the doctrine of the motion of the earth being now received, and a difficult question thereupon arising concerning the descent of heavy bodies, Galileus in our time, striving with that difficulty, was the first that opened to us the gate of natural philosophy universal, which is the knowledge of the nature of motion. So that neither can the age of natural philosophy be reckoned higher than to him." - Thomas Hobbes
"The first mathematician to consider the nature of the resistance of solids to rupture was Galileo. Although he treated solids as inelastic, not being in possession of any law connecting the displacements produced with the forces producing them, or of any physical hypothesis capable of yielding such a law, yet his enquiries gave the direction which was subsequently followed by many investigators." - Augustus Edward Hough Love
"If Galileo had been willing to face the idea of a plurality of worlds, instead of resting on that of the Sun as the natural "centre of things," he might have been impelled to develop his system in the Newtonian sense. ...The position of the satellites in the Copernican scheme proved the existence of a multiplicity of centers. But the way that led from there was fraught with danger." - Giorgio de Santillana
"To give us the science of motion God and Nature have joined hands and created the intellect of Galileo." - Paolo Sarpi
"The old Greek philosophy, which in Europe in the later middle ages was synonymous with the works of Aristotle, considered motion as a thing for which a cause must be found: a velocity required a force to produce and to maintain it. The great discovery of Galileo was that not velocity, but acceleration requires a force. This is the law of inertia of which the real content is: the natural phenomena are described by differential equations of the second order." - Willem de Sitter
Interests
Drawing, mythology, space observation, playing lute
Connections
Galileo Galilei was never married. However, he did have a brief relationship with Marina Gamba, a woman he met on one of his many trips to Venice. Marina lived in Galileo's house in Padua where she bore him three children, two daughters, Virginia (born in 1600) and Livia (born in 1601), and a son, Vincenzo (born in 1606).
Because of their illegitimate birth, their father considered the girls unmarriageable, if not posing problems of prohibitively expensive support or dowries, which would have been similar to Galileo's previous extensive financial problems with two of his sisters. Their only worthy alternative was religious life. Both girls were accepted by the convent of San Matteo in Arcetri and remained there for the rest of their lives. Virginia took the name Maria Celeste upon entering the convent. She died on 2 April 1634 and is buried with Galileo at the Basilica of Santa Croce, Florence. Livia took the name Sister Arcangela and was ill for most of her life. Vincenzo was later legitimized as the legal heir of Galileo and married Sestilia Bocchineri.
Father:
Vincenzo Galilei
Mother:
Giulia degli Ammannati Galilei
Daughter:
Livia Galilei
Daughter:
Virginia Galilei
Son:
Vincenzo (Gamba) Galilei
Partner:
Marina Gamba
Friend:
Lodovico Cardi da Cigoli
Cigoli and Galilei become acquainted at the Accademia delle Arti del Disegno in Florence. The two were lifelong friends.
Acquaintance:
Pope Urban VIII
Urban VII, original name Maffeo Barberini, was an Italian clergyman, who became the ruler of the Papal States from 1623 to 1644.
At first Barberini came to admire Galileo's intelligence and sharp wit. During a court dinner, in 1611, at which Galileo defended his view on floating bodies, Barberini supported Galileo against Cardinal Gonzaga. From this point, their patron-client relationship flourished until it was undone in 1633. Upon Barberini' s ascendance of the papal throne, in 1623, Galileo came to Rome and had six interviews with the new Pope. It was at these meetings that Galileo was given permission to write about the Copernican theory, as long as he treated it as a hypothesis. After the publication of Galileo' s Dialogue Concerning the Two Chief Systems of the World, in 1632, the patronage relationship was broken. It appears that the Pope never forgave Galileo for putting the argument of God's omnipotence in the mouth of Simplicio, the staunch Aristotelian whose arguments had been systematically destroyed in the previous 400-odd pages. At any rate, the Pope resisted all efforts to have Galileo pardoned.
Benedetto Castelli was a student, follower, and admirer of Galileo.
Friend:
Ascanio Piccolomini
Ascanio Piccolomini, the Archbishop of Siena, was a friend of Galileo. The scientist took refuge in Piccolomini's castle after his controversy over heliocentrism and trial.
