New ideas, especially in science, only move forward when men think and question about what they see to get a better understanding of it, deduce basic principles, etc., – and then, importantly, other people take these ideas up, and accept them as being true. It seems a steady but grindingly slow progress. The first philosophers were original thinkers, but later, other thinking men could stand on their shoulders and progress. But Galileo was a first. He really did take the tiger “of religious fixed ideas” by the tail and made a giant leap forward. Because of his inquiring mind, his deep thoughts and insights and discoveries, you can say with justification, that Galileo Galilei is the father of modern science.
Now, leading scientists see him as one of the greatest scientists of all time. His achievements include improvements to the telescope and that helped watching and observing the universe. This also helped with the idea that planet earth goes round the sun – heliocentrism. Galileo has been called the “father of modern observational astronomy“, and the “father of modern physics“, and “the father of modern science”.
He observed that Venus had phases and he discovered the four largest satellite moons of Jupiter (named the Galilean moons in his honour). He studied the dark spots on the sun and tried to understand them. Galileo also worked in applied science and technology, inventing an improved military compass and other instruments.
Galileo could see that we circled the sun but this was when most people thought the Earth was at the centre of the Universe! So, proclaiming, and writing that the earth went round the sun – heliocentrism and Copernicanism, was difficult to accept within his lifetime, and people opposed him! He met with opposition from other astronomers who wanted more proof of his ideas.
The matter was investigated by the Roman Catholic Church’s Inquisition in 1615. The judges thought that it was a possibility but not an established fact. Galileo later defended his views in Dialogue Concerning the Two Chief World Systems, but which also appeared to attack Pope Urban VIII, and so set the pope and the Jesuits against Galileo, when really, they had both supported Galileo up until this point.[9] He was tried by the Inquisition, found “vehemently (strongly) suspected of heresy”, forced to take back his words, and spent the rest of his life under house arrest. But, while Galileo was under house arrest, he wrote one of his finest books: Two New Sciences. In this he retold in short form the work he had done some forty years earlier, on the two sciences now called kinematics (force and momentum) and strength of materials.
Career as a scientist
As a young man, Galileo enrolled at the University of Pisa for a medical degree. He was a man who asked questions. As he was studying, he noticed a swinging light and noticed it swung in larger and smaller arcs according to the wind. When he compared the swings with his heartbeat he noticed the swings took the same amount of time, no matter how far it swung. He checked this with two pendulums of equal length, and swung one with a large sweep and the other with a small sweep. He noticed that they kept time with each other. It took another one hundred years for inventors to make an accurate clock from his idea.
Up to this time he had avoided mathematics as medicine paid better money. But after accidentally attending a lecture on geometry, he talked his reluctant father into letting him study mathematics and natural philosophy (science) instead of medicine.[23] He 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 (which first brought him to the attention of the scholarly world). Galileo also studied art and design and in 1588 obtained the position of instructor in the Accademia delle Arti del Disegno in Florence, Italy, teaching perspective and design. Being inspired by the artistic tradition of the city and the works of the Renaissance artists, Galileo acquired an aesthetic outlook. When he worked as a young teacher at the Accademia, he began a lifelong friendship with the Florentine painter Cigoli, who included Galileo’s lunar observations in one of his paintings.[24][25]
In 1589, he was appointed to the chair of mathematics in Pisa. In 1591, his father died, and he was entrusted with the care of his younger brother Michelagnolo. In 1592, he moved to the University of Padua where he taught geometry, mechanics, and astronomy until 1610.[26] During this period, Galileo made significant discoveries in both pure fundamental science (for example, kinematics of motion and astronomy) as well as practical applied science (for example, strength of materials and improvement of the telescope). His multiple interests included the study of astrology, which at the time was a discipline tied to the studies of mathematics and astronomy.[27]
Cardinal Bellarmine had written in 1615 that he wanted proof of the earth rotating around the sun. He wanted physical evidence. Galileo considered his theory of the tides of the Mediterranean provide the required physical proof of the motion of the earth. This theory was so important to him that he originally intended to entitle his Dialogue on the Two Chief World Systems the Dialogue on the Ebb and Flow of the Sea.[29] The reference to tides was removed 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. As a general account of the cause of tides, however, his theory was a failure.
Johannes Kepler, a scientist living at the same time as Galileo, said that the moon caused the world’s sea tides, but Galileo did not agree or accept his idea. He also refused to accept Kepler’s elliptical orbits of the planets,[34] considering the circle the “perfect” shape for planetary orbits.
Controversy over comets and The Assayer
In 1619, Galileo became caught in a public argument with Father Orazio Grassi, professor of mathematics at the Jesuit Collegio Romano. It began as a dispute over the nature of comets, but by the time Galileo had published his work: The Assayer in 1623, his final answer in the dispute, it had become a much wider argument over the very nature of science itself. The title (first) page of the book describes Galileo as philosopher and “Matematico Primario” to his eminence, the Grand Duke of Tuscany.
Because The Assayer contains such a wealth of Galileo’s ideas on how science should be practised, it has been referred to as his scientific manifesto.[35] Early in 1619, (four years before the Assayer) Father Grassi had anonymously published a pamphlet, An Astronomical Disputation on the Three Comets of the Year 1618, [36] which discussed the nature of a comet that had appeared late in November of the previous year. Grassi concluded that the comet was a fiery body which had moved along a segment of a great circle at a constant distance from the earth,[37] and since it moved in the sky more slowly than the moon, it must be farther away than the moon.
Grassi’s arguments and conclusions were criticised in a subsequent article, Discourse on the Comets,[38] published under the name of one of Galileo’s disciples, a Florentine lawyer named Mario Guiducci, although it had been largely written by Galileo himself.[39] Galileo and Guiducci offered no definitive theory of their own on the nature of comets[40] although they did present some tentative conjectures that are now known to be mistaken. In its opening passage, Galileo and Guiducci’s Discourse unnecessarily insulted the Jesuit Christopher Scheiner,[41] and unpleasant remarks about the professors of the Collegio Romano were scattered throughout the work! The Jesuits were offended, and Grassi soon replied with colourful language tract of his own, The Astronomical and Philosophical Balance,[44] under the pseudonym Lothario Sarsio Sigensano,[45] purporting to be one of his own pupils. (Note: a Jesuit is a highly educated Catholic priest, sworn to defend Catholicism and destroy others.)
The Assayer was Galileo’s devastating reply to the Astronomical and Philosophical Balance.[46] It has been widely recognized as a masterpiece of colourful literature, in which “Sarsi’s” arguments are subjected to withering scorn. It was greeted with wide praise, and it particularly pleased the new pope, Barberini or Pope Urban VIII, to whom it had been dedicated. In Rome, in the previous decade, the future Urban VIII, had come down on the side of (favoured) Galileo and the Lincean Academy.[50]
Galileo’s dispute with Grassi made huge enemies of the Jesuits who had previously been sympathetic to his ideas, and later, Galileo and his friends were convinced that these Jesuits were responsible for bringing about his later conviction of guilty of heresy against the church. However, this is thought of as doubtful.
Controversy over heliocentrism
In the Catholic world prior to Galileo’s conflict with the Church, the majority of educated people subscribed either (1) to the Aristotelian geocentric view that the earth was the center of the universe and that all heavenly bodies revolved around the Earth,[54] or (2) the Tychonic system that blended together geocentricsm with heliocentrism.
It was only in the 19th century (1800’s) that scientists, using better instrumentation, could observe it (although observations in the 18th century (1700’s) had already lead to widespread acceptance of heliocentrism). Though theories of heliocentrism had been circulating since antiquity, they had recently been revived by Nicolaus Copernicus. Since Copernicus’ system didn’t require the extensive use of epicycles that other theories did, it was simpler. There was no opposition to heliocentrism from any institution at the time, and as such was used by Pope Gregory XIII to reform the calendar in 1582.[57]
In the years after Copernicus, heliocentrism was a relatively uncontroversial. More dangerous (at least to Italians), was any opposition to papal authority, following the Catholic Church’s Counter Reformation effort and the wars, large and small, that would finally end with the terrible 30 Years War. Biblical references were sometimes used to attack heliocentrism, but Galileo defended heliocentrism, and in his Letter to the Grand Duchess Christina argued that it was not contrary to biblical texts. He took the Augustinian position that poetry, songs, instructions or historical statements in biblical texts need not always be interpreted literally. Galileo argued that the authors wrote from the perspective of the terrestrial world in which the sun does rise and set, and discussed a different kind of “movement” of the earth, not rotations.
By 1615 Galileo’s writings on heliocentrism had been submitted to the Roman Inquisition, though his greater offense[ was his attempt to reinterpret the Bible in order to get his discoveries accepted. This attempt was seen as a violation of the Council of Trent and looked dangerously like Protestantism.
In February 1616, an Inquisitorial commission declared heliocentrism to be “foolish and absurd in philosophy, and fully heretical since it explicitly contradicts in many places, the meanings of Holy (Bible) Scripture.” The Inquisition found that the idea of the Earth’s movement “receives the same judgement in philosophy and… in regard to theological truth it is at least incorrect – erroneous in faith.”[65] (The original document from the Inquisitorial commission was made widely available in 2014.[66])
Pope Paul V instructed Cardinal Bellarmine to deliver this finding to Galileo, and to order him to abandon opinion that heliocentrism was physically true. On 26 February, Galileo was called to Bellarmine’s residence and ordered:
“… to abandon completely… the opinion that the sun stands still at the center of the world and the earth moves, and henceforth not to hold, teach, or defend it in any way whatever, either orally or in writing.”
— The Inquisition’s injunction against Galileo, 1616.[67]
Galileo had alienated one of his biggest and most powerful supporters, the Pope, and was called to Rome to defend his writings[72] in September 1632. He finally arrived in February 1633 and was brought before inquisitor Vincenzo Maculani to be charged. His final interrogation, in July 1633, concluded with him being threatened with Inquisitional torture if he did not tell the truth, but he maintained his denial despite the threat.[73]
The sentence of the Inquisition was delivered on 22 June. It was in three parts:
- Galileo was found “vehemently suspect of heresy”, namely of having held the opinions that the Sun lies motionless at the centre of the universe, that the Earth is not at its centre and moves, and that one may hold and defend an opinion as probable after it has been declared contrary to Holy Scripture. He was required to “abjure, curse and detest” those opinions.[74]
- He was sentenced to formal imprisonment at the pleasure of the Inquisition.[75] On the following day this was commuted to house arrest, which he remained under for the rest of his life.
- His offending Dialogue was banned; and in an action not announced at the trial, publication of any of his works was forbidden, including any he might write in the future.[76]
He was forced to stay in his house, until death freed him from this torture.
Scientific methods
Galileo made original contributions to the science of motion through an innovative combination of experiment and mathematics.[89] Galileo’s father, Vincenzo Galilei, a lutenist and music theorist, had performed experiments establishing perhaps the oldest known non-linear relation in physics: for a stretched string, the pitch varies as the square root of the tension.[90]
These observations lay within the framework of the Pythagorean tradition of music, well-known to instrument makers, which included the fact that subdividing a string by a whole number produces a harmonious scale. Thus, a limited amount of mathematics had long related music and physical science, and young Galileo could see his own father’s observations expand on that tradition.[91]
Galileo was one of the first modern thinkers to clearly state that the laws of nature are mathematical. In The Assayer he wrote “Philosophy is written in this grand book, the universe … It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures;….”[92] His mathematical analyses are a further development of a tradition employed by late scholastic natural philosophers, which Galileo learned when he studied philosophy.[93] His work marked another step towards the eventual separation of science from both philosophy and religion; a major development in human thought. He was often willing to change his views in accordance with observation. In order to perform his experiments, Galileo had to set up standards of length and time, so that measurements made on different days and in different laboratories could be compared in a reproducible fashion. This provided a reliable foundation on which to confirm mathematical laws using inductive reasoning.
Galileo showed a modern appreciation for the proper relationship between mathematics, theoretical physics, and experimental physics. He understood the parabola, both in terms of conic sections and in terms of the ordinate (y) varying as the square of the abscissa (x). Galilei further asserted that the parabola was the theoretically ideal trajectory of a uniformly accelerated projectile in the absence of friction and other disturbances. He 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,[94] 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.[95]
Jupiter
On 7 January 1610, Galileo observed with his telescope what he described at the time as “three fixed stars, made totally invisible by their smallness”, all close to Jupiter, and lying on a straight line through it. He had discovered three of Jupiter’s four largest satellites (moons).
Later astronomers, renamed them Galilean satellites in honour of their discoverer. These satellites are now called Io, Europa, Ganymede, and Callisto.
His observations of the satellites of Jupiter caused a revolution in astronomy: a planet with smaller planets orbiting it did not conform to the principles of Aristotelian cosmology, which told that all heavenly bodies should circle the Earth, and many astronomers and philosophers initially refused to believe that Galileo could have discovered such a thing.[ His observations were confirmed by the observatory of Christopher Clavius and he received a hero’s welcome when he visited Rome in 1611.[106] 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 Kepler had believed impossible.[107]
Venus, Saturn, and Neptune
From September 1610, Galileo observed that Venus exhibited a full set of phases similar to that of the Moon. After Galileo’s telescopic observations of the crescent and full phases of Venus, therefore, this Ptolemaic model became untenable. Thus in the early 17th century as a result of his discovery the great majority of astronomers converted to one of the various geo-heliocentric planetary models,[108] such as the Tychonic, Capellan and Extended Capellan models,[109] each either with or without a daily rotating Earth.
Galileo observed the planet Saturn, and at first mistook its rings for planets, thinking it was a three-bodied system. When he observed the planet later, Saturn’s rings were directly oriented at Earth, causing him to think that two of the bodies had disappeared. The rings reappeared when he observed the planet in 1616, further confusing him.[110]
Galileo also observed the planet Neptune in 1612. It appears in his notebooks as one of many unremarkable dim stars. He did not realise that it was a planet, but he did note its motion relative to the stars before losing track of it.[111]
Sunspots
Galileo was one of the first Europeans to observe sunspots, although Kepler had unwittingly observed one in 1607, but mistook it for a transit of Mercury. The very existence of sunspots showed another difficulty with the unchanging perfection of the heavens as posited in orthodox Aristotelian celestial physics and as incorporated in the Bible. In fact, there is little doubt that both of them were beaten by David Fabricius and his son Johannes. Scheiner quickly adopted Kepler’s 1615 proposal of the modern telescope design, which gave larger magnification at the cost of inverted images; Galileo apparently never changed to Kepler’s design.
Moon
While not being the only one to observe the moon through a telescope, Galileo was the first to understand the cause of the uneven outlines as light shadows made by lunar mountains and craters. In his study he also made land layout charts, estimating the heights of the mountains. The moon was not what was long thought to have been a translucent and perfect sphere, as Aristotle claimed, and hardly the first “planet”, an “eternal pearl to magnificently ascend into the heavenly empyrian”, as put forth by Dante.
Milky Way and stars
Galileo observed the Milky Way, which had previously believed to be cotton-cloud-like, and found it to be a multitude of stars packed so densely that they appeared from Earth to be clouds. He located many other stars too distant to be visible with the naked eye. He observed the double star Mizar in Ursa Major in 1617.[114]
Like most astronomers of his day, Galileo did not realize that sizes of stars that he measured were incorrect due to diffraction and atmospheric distortion, and his estimates did not represent the true sizes of stars.
Death
Galileo continued to receive visitors until 1642, when, after suffering fever and heart palpitations, he died on 8 January 1642, aged 77.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 honour.[82]These plans were cancelled, after Pope Urban VIII and his nephew, Cardinal Francesco Barberini, protested, because Galileo had been convicted by the Catholic Inquisition for “vehement suspicion of heresy”.[84] 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.
Taken from Wikipedia. The full article is about 20 pages. ROS. 8/9/2015