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Galileo Galilei

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                    Galileo Galilei
   Portrait of Galileo Galilei by Giusto Sustermans.
   Born February 15, 1564
        Pisa
   Died January 8, 1642
        Arcetri

   Galileo Galilei ( 15 February 1564 – 8 January 1642) was an Italian
   physicist, astronomer, and philosopher who is closely associated with
   the scientific revolution. His achievements include improvements to the
   telescope, a variety of astronomical observations, and effective
   support for Copernicanism. According to Stephen Hawking, Galileo has
   probably contributed more to the creation of the modern natural
   sciences than anybody else. He has been referred to as the " father of
   modern astronomy," as the "father of modern physics", and as the
   "father of science". The work of Galileo is considered to be a
   significant break from that of Aristotle.

Biographical Sketch

   Galileo was born in Pisa, in the Tuscany region of Italy, on February
   15, 1564, the son of Vincenzo Galilei. Galileo was their first child
   out of seven (some people believe six). Most authorities say he was the
   most talented of the children.

   Galileo was tutored from a very young age. Later, he attended the
   University of Pisa but was forced to halt his studies there for
   financial reasons. However, he was offered a position on its faculty in
   1589 and taught mathematics. Soon after, he moved to the University of
   Padua and served on its faculty, teaching geometry, mechanics, and
   astronomy until 1610. During this period he concentrated on science,
   and made many significant discoveries.

   Although he was a devout Roman Catholic, Galileo fathered three
   children out of wedlock with Marina Gamba. They had two daughters
   (Virginia and Livia) and one son (Vincenzio). Because of their
   illegitimate birth, both girls were sent to the convent of San Matteo
   in Arcetri at early ages and remained there for the rest of their
   lives. Virginia took the name Maria Celeste upon entering the convent.
   She was Galileo's eldest child, the most beloved, and inherited her
   father's sharp mind. She died on April 2, 1634, and is currently buried
   with Galileo at the Basilica di Santa Croce di Firenze. Livia (b. 1601)
   took the name Suor Arcangela, made no great impact on the world, and
   was ill for most of her life. Vincenzio (b. 1606) was later legitimized
   and married Sestilia Bocchineri.

   In 1612, Galileo went to Rome, where he joined the Accademia dei Lincei
   and observed sunspots. In 1612, opposition arose to the Copernican
   theories, which Galileo supported. In 1614, from the pulpit of Santa
   Maria Novella, Father Tommaso Caccini (1574-1648) denounced Galileo's
   opinions on the motion of the Earth, judging them dangerous and close
   to heresy. Galileo went to Rome to defend himself against these
   accusations, but, in 1616, Cardinal Roberto Bellarmino personally
   handed Galileo an admonition enjoining him to neither advocate nor
   teach Copernican astronomy as religious doctrine. In 1622, Galileo
   wrote the The Assayer (Saggiatore), which was approved and published in
   1623. In 1624, he developed the first known example of the microscope.
   In 1630, he returned to Rome to apply for a license to print the
   Dialogue Concerning the Two Chief World Systems, published in Florence
   in 1632. In October of that year, however, he was ordered to appear
   before the Holy Office in Rome. The court issued a sentence of
   condemnation and forced Galileo to abjure. As a result, he was confined
   in Siena and eventually, in December 1633, he was allowed to retire to
   his villa in Arcetri. In 1634, he was deprived of the support of his
   beloved daughter, Sister Maria Celeste (1600-1634), who died
   prematurely. In 1638, almost totally blind, Galileo published his final
   book, Two New Sciences, in Leiden. He died in Arcetri on the January 8,
   1642, in the company of his student Vincenzo Viviani.

Scientific methods

   In the pantheon of the scientific revolution, Galileo Galilei takes a
   high position because of his pioneering use of quantitative experiments
   with results analyzed mathematically. There was no tradition of such
   methods in European thought at that time; the great experimentalist who
   immediately preceded Galileo, William Gilbert, did not use a
   quantitative approach. However, Galileo's father, Vincenzo Galilei, a
   lutenist and music theorist, had performed experiments in which he
   discovered what may be the oldest known non-linear relation in physics,
   between the tension and the pitch of a stretched string. These
   observations were in the Pythagorean tradition of music, well-known to
   instrument makers, that whole-number mathematical relationships define
   harmonious (pleasing) scales. Thus, a limited form of mathematics had
   long made its way into physical science at the point of music, and
   young Galileo was in a position to see his own father's observations
   generalize that relationship still further. Galileo himself would find
   credit as the first to plainly state that the laws of nature are
   mathematical, and (as he said) the idea that "the language of God is
   mathematics." This was a sharp break with earlier traditions of
   science: up until this point, following Aristotle, logic, not
   mathematics had been seen to be the basic intellectual tool of science.

   Galileo also contributed to the rejection of blind allegiance to
   authority (like the Church) or other thinkers (such as Aristotle) in
   matters of science and to the separation of science from philosophy or
   religion. These are the primary justifications for his description as
   the "father of science".

   In the 20th century some authorities, in particular the distinguished
   French historian of science Alexandre Koyré, challenged the validity of
   Galileo's experiments. The experiments reported in Two New Sciences to
   determine the law of acceleration of falling bodies, for instance,
   required accurate measurements of time, which appeared to be impossible
   with the technology of the 1600s. According to Koyré, the law was
   arrived at deductively, and the experiments were merely illustrative
   thought experiments.

   Later research, however, has validated the experiments. The experiments
   on falling bodies (actually rolling balls) were replicated using the
   methods described by Galileo (Settle, 1961), and the precision of the
   results were consistent with Galileo's report. Later research into
   Galileo's unpublished working papers from as early as 1604 clearly
   showed the validity of the experiments and even indicated the
   particular results that led to the time-squared law (Drake, 1973).

   He had even attempted to measure the speed of light. He did it in an
   ingenious way.
     * He climbed up a hill and told someone else to climb up another
       hill. They both had lanterns with shutters.
     * He then opened the shutter of his lantern and counted to see how
       long it took for the other person to open theirs.
     * Using mathematics, he tried to work out how fast the light was
       travelling.

   But when he tried to repeat the experiment with hills further apart, he
   still got the same time lapse. This was because he was measuring the
   reaction time of the person.

   Galileo showed a remarkably modern appreciation for the proper
   relationship between mathematics, theoretical physics, and experimental
   physics. For example:
     * He understood the mathematical parabola, both in terms of conic
       sections and in terms of the square-law.
     * He asserted that the parabola was the theoretically-ideal
       trajectory, in the absence of friction and other disturbances. More
       remarkably, he stated limits to the validity of this theory, saying
       that it was appropriate for laboratory-scale and battlefield-scale
       trajectories. He went on to point out, on theoretical physics
       grounds, that the parabola could not possibly be correct if the
       trajectory were so large as to be comparable to the size of the
       planet. ( Two New Sciences, page 274 of the National Edition)
     * He recognized that his experimental data would never agree exactly
       with any theoretical or mathematical form, because of the
       imprecision of measurement, irreducible friction, and other
       factors.

   Due to the merit of his works, Einstein called Galileo the "father of
   modern science".

Astronomy

Contributions

   The belief that Galileo invented the telescope is a common
   misconception. However, he improved the device, was one of the first to
   use it to observe the sky, and for a time was one of very few people
   able to construct one good enough for that purpose. Based only on
   sketchy descriptions of the telescope, invented in the Netherlands in
   1608, Galileo made one with about 3x magnification, and then made
   improved models up to about 32x. On August 25, 1609, he demonstrated
   his first telescope to Venetian lawmakers. His work on the device also
   made for a profitable sideline with merchants who found it useful for
   their shipping businesses. He published his initial telescopic
   astronomical observations in March 1610 in a short treatise entitled
   Sidereus Nuncius (Starry Messenger).
   It was on this page that Galileo first noted an observation of the
   moons of Jupiter. This observation upset the notion that all celestial
   bodies must revolve around the Earth. Galileo published a full
   description in Sidereus Nuncius in March 1610.
   Enlarge
   It was on this page that Galileo first noted an observation of the
   moons of Jupiter. This observation upset the notion that all celestial
   bodies must revolve around the Earth. Galileo published a full
   description in Sidereus Nuncius in March 1610.

   In the week of January 7, 1610 Galileo discovered three of Jupiter's
   four largest satellites (moons): Io, Europa, and Callisto. He
   discovered Ganymede four nights later. He noted that the moons would
   appear and disappear periodically, an observation which he attributed
   to their movement behind Jupiter, and concluded that they were orbiting
   the planet. He made additional observations of them in 1620. Later
   astronomers overruled Galileo's naming of these objects, changing his
   originally named Medicean stars (after his patrons, the Medici) to
   Galilean satellites. The demonstration that a planet had smaller
   planets orbiting it was problematic for the orderly, comprehensive
   picture of the geocentric model of the universe, in which everything
   circled around the Earth.

   From September 1610 Galileo observed that Venus exhibited a full set of
   phases similar to that of the Moon. The heliocentric model of the solar
   system developed by Copernicus predicted that all phases would be
   visible since the orbit of Venus around the Sun would cause its
   illuminated hemisphere to face the Earth when it was on the opposite
   side of the Sun and to face away from the Earth when it was on the
   Earth-side of the Sun. In contrast, the geocentric model of Ptolemy
   predicted that only crescent and new phases would be seen, since Venus
   was thought to remain between the Sun and Earth during its orbit around
   the Earth. Galileo's observations of the phases of Venus proved that it
   orbited the Sun and lent support to (but did not prove) the
   heliocentric model.

   Galileo was one of the first Europeans to observe sunspots. He also
   reinterpreted a sunspot observation from the time of Charlemagne, which
   formerly had been attributed (impossibly) to a transit of Mercury. The
   very existence of sunspots showed another difficulty with the
   unchanging perfection of the heavens as assumed in the older
   philosophy. And the annual variations in their motions, first noticed
   by Francesco Sizi, presented great difficulties for both the geocentric
   system and that of Tycho Brahe. A dispute over priority in the
   discovery of sunspots led Galileo to a long and bitter feud with
   Christoph Scheiner; in fact, there is little doubt that both of them
   were beaten by David Fabricius and his son Johannes.

   Galileo was also the first to report lunar mountains and craters, whose
   existence he deduced from the patterns of light and shadow on the
   Moon's surface. He even estimated the mountains' heights from these
   observations. This led him to the conclusion that the Moon was "rough
   and uneven, and just like the surface of the Earth itself," rather than
   a perfect sphere as Aristotle had claimed.

   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 to be clouds from Earth. He also located many other stars too
   distant to be visible with the naked eye.

   Galileo observed the planet Neptune in 1612, but did not realize that
   it was a planet and took no particular notice of it. It appears in his
   notebooks as one of many unremarkable dim stars.

Galileo, Kepler, and theories of tides

   Galileo never accepted Kepler's elliptical orbits of the planets,
   despite Kepler's tremendous amount of data collected by Tycho Brahe,
   considering the circle a "perfect" shape. While the Copernican theory
   used epicycles to account for the variations, which added a great deal
   of complexity, Kepler's model did not.

   Galileo attributed tides to momentum, as opposed to Kepler's theories
   which used the moon as a cause. (Neither of these great scientists,
   however, had a workable physical theory of tides; this had to wait for
   the work of Newton.) Galileo stated in his Dialogue that, if the Earth
   spins on its axis and is travelling at a certain speed around the Sun,
   parts of the Earth must travel "faster" at night and "slower" during
   the day.

   If this theory were correct, there would be only one high tide per day
   at noon. Galileo and his contemporaries were aware of this inadequacy
   because there are two daily high tides at Venice instead of one, and
   they travel around the clock. But Galileo dismissed this anomaly as the
   result of several secondary causes, including the shape of the sea, its
   depth, and other things. Against the assertion that Galileo was
   deceptive in making these arguments, Albert Einstein developed 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 (Einstein, 1952).

   The noted author Arthur Koestler, in his book ' The Sleepwalkers',
   argued that Galileo was grossly unscientific and dishonest in his
   methods, and rarely gave credit where due. Others argue that it is
   unfair to hold him to modern "scientific standards" (mathematical
   theory supported by evidential trial) with which he himself was only
   beginning to experiment. By the standards of his own time, Galileo was
   often willing to change his views in accordance with observation. It
   may also be argued that all modern scientists (not to mention other
   professionals) filter their observations and beliefs through
   pre-conceived notions. Although this may appear "dishonest", some of it
   is actually required for the scientific process to function (see Bayes
   theorem). Galileo's perceived dishonesty, then, is not abnormal.

Physics

   Galileo's theoretical and experimental work on the motions of bodies,
   along with the largely independent work of Kepler and René Descartes,
   was a precursor of the Classical mechanics developed by Sir Isaac
   Newton. He was a pioneer, at least in the European tradition, in
   performing rigorous experiments and insisting on a mathematical
   description of the laws of nature.

   One of the most famous stories about Galileo is that he dropped balls
   of different masses from the Leaning Tower of Pisa to demonstrate that
   their time of descent was independent of their mass (excluding the
   limited effect of air resistance). This was contrary to what Aristotle
   had taught: that heavy objects fall faster than lighter ones, in direct
   proportion to weight. Though the story of the tower first appeared in a
   biography by Galileo's pupil Vincenzo Viviani, it is not now generally
   accepted as true. Moreover, Giambattista Benedetti had reached the same
   scientific conclusion years before, in 1553. However, Galileo did
   perform experiments involving rolling balls down inclined planes, one
   of which is in Florence, called the bell and ball experiment, which
   proved the same thing: falling or rolling objects (rolling is a slower
   version of falling, as long as the distribution of mass in the objects
   is the same) are accelerated independently of their mass. (Although
   Galileo was the first person to demonstrate this via experiment, he was
   not — contrary to popular belief — the first to argue that it was true.
   John Philoponus had argued this centuries earlier: see also the Oxford
   Calculators).

   He determined the correct mathematical law for acceleration: the total
   distance covered, starting from rest, is proportional to the square of
   the time ( d \propto t^2 ). He expressed this law using geometrical
   constructions and mathematically-precise words, adhering to the
   standards of the day. (It remained for others to re-express the law in
   algebraic terms.) He also concluded that objects retain their velocity
   unless a force — often friction — acts upon them, refuting the
   generally accepted Aristotelian hypothesis that objects "naturally"
   slow down and stop unless a force acts upon them (again this was not a
   new idea: Ibn al-Haitham had proposed it centuries earlier, as had Jean
   Buridan, and according to Joseph Needham, Mo Tzu had proposed it
   centuries before either of them, but this was the first time that it
   had been mathematically expressed). Galileo's Principle of Inertia
   stated: "A body moving on a level surface will continue in the same
   direction at constant speed unless disturbed." This principle was
   incorporated into Newton's laws of motion (first law).
   Dome of the cathedral of Pisa with the "lamp of Galileo"
   Enlarge
   Dome of the cathedral of Pisa with the "lamp of Galileo"

   Galileo also noted that a pendulum's swings always take the same amount
   of time, independently of the amplitude. The story goes that he came to
   this conclusion by watching the swings of the bronze chandelier in the
   cathedral of Pisa, using his pulse to time it. While Galileo believed
   this equality of period to be exact, it is only an approximation
   appropriate to small amplitudes. It is good enough to regulate a clock,
   however, as Galileo may have been the first to realize. (See Technology
   below)

   In the early 1600s, Galileo and an assistant tried to measure the speed
   of light. They stood on different hilltops, each holding a shuttered
   lantern. Galileo would open his shutter, and, as soon as his assistant
   saw the flash, he would open his shutter. At a distance of less than a
   mile, Galileo could detect no delay in the round-trip time greater than
   when he and the assistant were only a few yards apart. While he could
   reach no conclusion on whether light propagated instantaneously, he
   recognized that the distance between the hilltops was perhaps too small
   for a good measurement.

   Galileo is lesser known for, yet still credited with being one of the
   first to understand sound frequency. After scraping a chisel at
   different speeds, he linked the pitch of sound to the spacing of the
   chisel's skips (frequency).

   In his 1632 Dialogue Galileo presented a physical theory to account for
   tides, based on the motion of the Earth. If correct, this would have
   been a strong argument for the reality of the Earth's motion. (The
   original title for the book, in fact, described it as a dialogue on the
   tides; the reference to tides was removed by order of the Inquisition.)
   His 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. As a general account of the cause of
   tides, however, his theory was a failure. Kepler and others correctly
   associated the Moon with an influence over the tides, based on
   empirical data; a proper physical theory of the tides, however, was not
   available until Newton.

   Galileo also 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. Hence, there is no absolute motion or absolute rest. This
   principle provided the basic framework for Newton's laws of motion and
   is the infinite speed of light approximation to Einstein's special
   theory of relativity.

Mathematics

   While Galileo's application of mathematics to experimental physics was
   innovative, his mathematical methods were the standard ones of the day.
   The analysis and proofs relied heavily on the Eudoxian theory of
   proportion, as set forth in the fifth book of Euclid's Elements. This
   theory had become available only a century before, thanks to accurate
   translations by Tartaglia and others; but by the end of Galileo's life
   it was being superseded by the algebraic methods of Descartes.

   Galileo produced one piece of original and even prophetic work in
   mathematics: Galileo's paradox, which shows that there are as many
   perfect squares as there are whole numbers, even though most numbers
   are not perfect squares. Such seeming contradictions were brought under
   control 250 years later in the work of Georg Cantor.

Technology

   Galileo Galilei.
   Enlarge
   Galileo Galilei.
   A replica of the earlest surviving telescope attributed to Galileo
   Galilei, on display at the Griffith Observatory
   Enlarge
   A replica of the earlest surviving telescope attributed to Galileo
   Galilei, on display at the Griffith Observatory

   Galileo made a few contributions to what we now call technology as
   distinct from pure physics, and suggested others. This is not the same
   distinction as made by Aristotle, who would have considered all
   Galileo's physics as techne or useful knowledge, as opposed to
   episteme, or philosophical investigation into the causes of things.

   In 1595–1598, Galileo devised and improved a "Geometric and Military
   Compass" suitable for use by gunners and surveyors. This expanded on
   earlier instruments designed by Niccolo Tartaglia and Guidobaldo del
   Monte. For gunners, it offered, in addition to a new and safer way of
   elevating cannons accurately, a way of quickly computing the charge of
   gunpowder for cannonballs of different sizes and materials. As a
   geometric instrument, it enabled the construction of any regular
   polygon, computation of the area of any polygon or circular sector, and
   a variety of other calculations.

   About 1606–1607 (or possibly earlier), Galileo made a thermometer,
   using the expansion and contraction of air in a bulb to move water in
   an attached tube.

   In 1609, Galileo was among the first to use a refracting telescope as
   an instrument to observe stars, planets or moons.

   In 1610, he used a telescope as a compound microscope, and he made
   improved microscopes in 1623 and after. This appears to be the first
   clearly documented use of the compound microscope.

   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. He worked on this
   problem from time to time during the remainder of his life; but the
   practical problems were severe. The method was first successfully
   applied by Giovanni Domenico Cassini in 1681 and was later used
   extensively for large land surveys; this method, for example, was used
   by Lewis and Clark. (For sea navigation, where delicate telescopic
   observations were more difficult, the longitude problem eventually
   required development of a practical portable chronometer, such as that
   of John Harrison).

   In his last year, when totally blind, he designed an escapement
   mechanism for a pendulum clock. The first fully operational pendulum
   clock was made by Christiaan Huygens in the 1650s.

   He created sketches of various inventions, such as a candle and mirror
   combination to reflect light throughout a building, an automatic tomato
   picker, a pocket comb that doubled as an eating utensil, and what
   appears to be a ballpoint pen.

Church controversy

   Cristiano Banti's 1857 painting Galileo facing the Roman Inquisition
   Enlarge
   Cristiano Banti's 1857 painting Galileo facing the Roman Inquisition

   Psalms 93:1; 96:10; 104:5, 1Chronicles 16:30 and Ecclesiastes 1:4,5
   speak of the (in some sense) "firm" and "established" position of the
   earth. Galileo defended heliocentrism, and claimed it was not contrary
   to those Scripture passages. He took Augustine's position on Scripture:
   not to take every passage too literally, particularly when the
   scripture in question is a book of poetry and songs, not a book of
   instructions or history. The writers of the Scripture wrote from the
   perspective of the terrestrial world, and from that vantage point the
   sun does rise and set. In fact, it is the earth's rotation which gives
   the impression of the sun in motion across the sky.

   By 1616 the attacks on Galileo had reached a head, and he went to Rome
   to try to persuade the Church authorities not to ban his ideas. In the
   end, Cardinal Bellarmine, acting on directives from the Inquisition ,
   delivered him an order not to "hold or defend" the idea that the Earth
   moves and the Sun stands still at the centre. The decree did not
   prevent Galileo from hypothesizing heliocentrism. For the next several
   years Galileo stayed well away from the controversy.

   He revived his project of writing a book on the subject, encouraged by
   the election of Cardinal Barberini as Pope Urban VIII in 1623.
   Barberini was a friend and admirer of Galileo, and had opposed the
   condemnation of Galileo in 1616. The book, Dialogue Concerning the Two
   Chief World Systems, was published in 1632, with formal authorization
   from the Inquisition and papal permission.

   Pope Urban VIII personally asked Galileo to give arguments for and
   against heliocentrism in the book, and to be careful not to advocate
   heliocentrism. He made another request, that his own views on the
   matter be included in Galileo's book. Only the latter of those requests
   was fulfilled by Galileo. Whether unknowingly or deliberate,
   Simplicius, the defender of the Aristotelian Geocentric view in
   Dialogue Concerning the Two Chief World Systems, was often caught in
   his own errors and sometimes came across as a fool. This fact made
   Dialogue Concerning the Two Chief World Systems appear as an advocacy
   book; an attack on Aristotelian geocentrism and defense of the
   Copernican theory. To add insult to injury, Galileo put the words of
   Pope Urban VIII into the mouth of Simplicius. Most historians agree
   Galileo did not act out of malice and felt blindsided by the reaction
   to his book. However, the Pope did not take the public ridicule
   lightly, nor the blatant bias. Galileo had alienated one of his biggest
   and most powerful supporters, the Pope, and was called to Rome to
   explain himself.

   With the loss of many of his defenders in Rome because of Dialogue
   Concerning the Two Chief World Systems, Galileo was ordered to stand
   trial on suspicion of heresy in 1633. The sentence of the Inquisition
   was in three essential parts:
     * Galileo was required to recant his heliocentric ideas; the idea
       that the Sun is stationary was condemned as "formally heretical".
     * He was ordered imprisoned; the sentence was later commuted to house
       arrest.
     * His offending Dialogue was banned; and in an action not announced
       at the trial and not enforced, publication of any of his works was
       forbidden, including any he might write in the future.

   After a period with the friendly Ascanio Piccolomini (the Archbishop of
   Siena), Galileo was allowed to return to his villa at Arcetri near
   Florence, where he spent the remainder of his life under house arrest,
   dying on January 8, 1642. It was while Galileo was under house arrest
   when he dedicated his time to one of his finest works, Two New
   Sciences. This book has received high praise from both Sir Isaac Newton
   and Albert Einstein. As a result of this work, Galileo is often called,
   the "father of modern physics".
   Tomb of Galileo Galilei, Santa Croce
   Enlarge
   Tomb of Galileo Galilei, Santa Croce

   Galileo was reburied on sacred ground at Santa Croce in 1737. He was
   formally rehabilitated in 1741, when Pope Benedict XIV authorized the
   publication of Galileo's complete scientific works (a censored edition
   had been published in 1718), and in 1758 the general prohibition
   against heliocentrism was removed from the Index Librorum Prohibitorum.
   On 31 October 1992, Pope John Paul II expressed regret for how the
   Galileo affair was handled, as the result of a study conducted by the
   Pontifical Council for Culture.

   In modern scientific terms, we consider Galileo's views on
   heliocentricity to be no fundamental advance. Most of his discoveries
   were only further advances of Copernicus' views. The heliocenticity
   model that Galileo presented was no more accurate than the Tychonic
   system model, the main competing theory at the time. Stellar parallax,
   the first evidence from outside the solar system that the Earth does
   indeed move, would not be observed until 1838 (Consolmagno 150-152).
   Today, we know the Sun is no more the centre of the universe than the
   Earth is, as it has its own orbit in the Milky Way Galaxy, just like
   the Galilean moons of Jupiter have orbits around Jupiter while Jupiter
   orbits the Sun. He found this because he realized that the only orbit
   the moons could follow is that which orbits behind Jupiter.

Galileo's writings

   Statue outside the Uffizi, Florence
   Enlarge
   Statue outside the Uffizi, Florence
     * The Little Balance 1586
     * The Starry Messenger 1610 Venice (in Latin, Sidereus Nuncius)
     * Letters on Sunspots 1613
     * Letter to Grand Duchess Christina 1615
     * The Assayer (In Italian, Il Saggiatore) 1623
     * Dialogue Concerning the Two Chief World Systems 1632 (in Italian,
       Dialogo dei due massimi sistemi del mondo)
     * Two New Sciences 1638 Lowys Elzevir (Louis Elsevier) Leiden (in
       Italian, Discorsi e Dimostrazioni Matematiche, intorno a due nuoue
       scienze Leida, Appresso gli Elsevirii 1638)

Galileo in popular culture

     * The Star Gazer, a novel by Zsolt De Harsanyi, published by G. P.
       Putnam's Sons, 1939 (translated from the Hungarian by Paul Tabor)
     * Life of Galileo, a play by Bertolt Brecht, 1940
     * Lamp at Midnight, a tv play by Barrie Stavis, on George Schaefer's
       Showcase Theatre, NBC, 1966
     * " Galileo's Cannonball", the first episode the Nickelodeon game
       show Legends of the Hidden Temple, 1993
     * "Advantage, Bellarmine", a short story by Paul Levinson, published
       in Analog magazine, January 1998
     * Galileo's Daughter, a memoir by Dava Sobel, 2000
     * Galileo Galilei (play), a play by Mehmet Murat İldan, 2001
     * Galileo Galilei, an opera by Philip Glass, Mary Zimmerman, and
       Arnold Weinstein, 2002
     * Galileo, a pop song by the Indigo Girls.
     * Galileo is mentioned in Queen's song "Bohemian Rhapsody"

Named after Galileo

     * Galileo (unit of acceleration)
     * Galileo positioning system
     * Galileo Galilei Airport in the Italian city of Pisa
     * Galilei number ( fluid dynamics)
     * The Galileo mission to Jupiter
     * The Galilean moons of Jupiter
     * Galileo Regio on Ganymede
     * Galileo stadium in Miami, Florida
     * Galileo High School in San Francisco, California
     * Galilaei crater on the Moon
     * Galilaei crater on Mars
     * Asteroid 697 Galilea (named on the occasion of the 300th
       anniversary of the discovery of the Galilean moons)
     * Galileo Commissions processing system at Sesame

Footnote

    1. ^ Starry Messenger. Galileo's Telescope

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