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{{Image|Galileo Galilei.jpg|right|350px|left|Galileo, describing himself as a member of the Lincean Academy and Philosopher and Mathematician to the Grand Duke of Tuscany, depicted on the title page of his ''Letters on Sunspots'' (1613). }}
{{Image|Classical mechanics timeline.PNG|right|250px|Timeline for key scientists in classical mechanics}}
'''Galileo Galilei''' (1564-1642) was an [[Italy|Italian]] [[Science|scientist]] who was a major figure in the [[Scientific Revolution]]. He was a pioneer in the modern combination of mathematical theory with systematic experiment in science.


'''Galileo Galilei''' ([[February 15]], [[1564]] - [[January 8]], [[1642]]), was an [[Italy|Italian]] [[astronomy|astronomer]], [[philosopher]], and [[physics|physicist]], and one of the most famous figures in the [[History of scientific method|Scientific Revolution]]. He has been referred to as the "father of modern [[astronomy]]", as the "father of modern [[physics]]", and as the "father of [[science]]". (These claims are also made on behalf of others, including [[Johannes Kepler|Kepler]] for his astronomical work and [[Francis Bacon]] for his theoretical writings on scientific method.) Galileo's combination of systematic experiment with mathematical analysis was contrary to the thinking of his time, which was based on the work of [[Aristotle]]; it has since been considered fundamental to exact scientific work.
His work in [[physics]] included experimentation to establish the behavior of falling bodies, as well as the first modern theoretical work on [[inertia]] (for which he was given credit by [[Isaac Newton|Newton]]) and [[relativity]] of motion (for which he was credited by [[Albert Einstein|Einstein]]).


He was one of the first [[astronomy|astronomers]] to use a [[telescope]], and the discoverer or co-discoverer of several phenomena that contradicted the accepted ideas of the heavens. His support of the [[Nicolaus Copernicus|Copernican]] idea that the [[Earth]] revolves around the [[Sun]] led to a trial before the [[Inquisition]] on a suspicion of [[heresy]].


==Experimental science==
==Experimental science==


In the pantheon of the [[scientific revolution]] Galileo occupies a
Among the figures of the [[scientific revolution]] Galileo occupies a
high position because of his pioneering use of quantitative experiments  
high position because of his pioneering use of quantitative experiments
with results analyzed mathematically. There was no tradition of such methods
with results analyzed mathematically. There was no tradition of such
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]], 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.)
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, the musician
[[Vincenzo Galilei]], 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.)


In the [[20th century]] the reality of Galileo's experiments was challenged by some authorities, in particular the distinguished French [[History of science and technology|historian of science]] [[Alexandre Koyré]]. 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 have been impossible with the technology of 1600. According to Koyré, the law was arrived at deductively, and the experiments were merely illustrative thought experiments.
In the [[20th century]] the reality of Galileo's experiments was
challenged by some authorities, in particular the distinguished French
[[History of science and technology|historian of science]]  
[[Alexandre Koyré]]. 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 have been impossible
with the technology of 1600. According to Koyré, the law was arrived at
deductively, and Galileo's experiments, reported in some detail as if actually performed, 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 was consistent with Galileo's report. Later research into Galileo's unpublished working papers from as early as [[1604]]
Later research, however, has validated the experiments. The measurements
clearly showed the reality of the experiments and even indicated the particular results that led to the time-squared law (Drake, 1973).
on falling bodies (actually rolling balls) were replicated using the
methods described by Galileo,<ref> Settle, Thomas B. (1961). "An Experiment in the History of Science". ''Science'', 133:19-23.</ref> and the precision of the
results was consistent with Galileo's report. Later research into
Galileo's unpublished working papers from as early as 1604 clearly
showed the reality of the experiments and even indicated the particular
results that led to the time-squared law.<ref name=Drake1973>Drake, Stillman (1973). "Galileo's Discovery of the Law of Free Fall". ''Scientific American'' v. 228, #5: 84-92</ref>


== Astronomy ==
== Astronomy ==


Galileo was one of the first people to use the [[telescope]] to observe the [[sky]]. Based on sketchy descriptions of existing telescopes, he made one with about 8x magnification, and then made improved models up to about 20x. He published his initial telescopic [[observation]]s in March [[1610]] in a short treatise entitled ''[[Sidereus Nuncius]]'' (''Sidereal Messenger'').
In July of 1609 Galileo heard a report that a traveler from [[Flanders]] had shown "a glass by means of which distant objects could be seen as distinctly as if they were nearby." This person or another traveler then negotiated with the government of Venice to sell his secret device at a high price. A telescope had in fact been the subject of a patent application the previous year by [[Hans Lippershey]], a [[Netherlands|Dutch]] spectacle maker, and had been known for months to Galileo's friend [[Paolo Sarpi]]. (Compare the story, found not only in [[Bertolt Brecht|Brecht's]] play "Galileo" but in some authors claiming to give a historical
account,<ref>http://www.catholiceducation.org/articles/history/world/wh0005.html</ref> that Galileo attempted to claim full credit for the invention of the telescope.) Without seeing the telescope, Galileo soon figured out how to make a crude one, which was followed by series of improvements, including an 8-power telescope and one of 20 power, probably in November of 1609.<ref>Drake (1978); pp. 137&ndash;143</ref> 


[[image:galileo.script.arp.600pix.jpg|thumb|200px|right|Galileo Galilei's discovery of the moons of Jupiter. This is a manuscript page, in Italian, on which Galileo first noted an observation of the moons; a full description of them appeared in Sidereus Nuncius in March 1610. For a translation from Sidereus Nuncius click on the picture.]]
Before the start of 1610 Galileo was using his telescopes to observe the [[Moon]] and stars.<ref>'''<u>Note:</u>''' Year 2009 marks the 400th anniversary of Galileo's first use of the telescope, which enabled his revolutionizing astronomy.  It also marks the 200th anniversary of [[Charles Darwin|Charles Darwin's]] birth, enabling his revolution of biology.</ref> He soon saw that the line of shadow separating the light and dark sides of the moon (the terminator) was highly irregular and moved in an irregular fashion, leading to the conclusion that the surface was rough, contrary to the unanimous belief at that time that all heavenly bodies were perfectly spherical and smooth. By measuring shadows he estimated the height of lunar mountains with reasonable accuracy, and noted that they seemed to be higher than terrestrial
ones.<ref>Galilei (1610); pp. 32&ndash;41</ref>


On [[January 7]]th [[1610]] Galileo discovered Jupiter's four largest [[natural satellite|satellite]]s (moons): [[Io (moon)|Io]], [[Europa (moon)|Europa]], [[Ganymede (moon)|Ganymede]], and [[Callisto (moon)|Callisto]]. He determined that these moons were [[orbit]]ing the [[planet]] since they would occasionally disappear; something he attributed to their movement behind Jupiter.  He made additional observations of them in [[1620]].  (Later astronomers overruled Galileo's naming of these objects, changing his ''Medicean stars'' 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.
In January 1610 Galileo discovered Jupiter's four largest [[natural satellite|satellite]]s
(moons): [[Io (moon)|Io]], [[Europa (moon)|Europa]], [[Ganymede (moon)|Ganymede]], and  
[[Callisto (moon)|Callisto]]. Over the succeeding months he was able to determine the orbital periods of the satellites, and he made additional
observations to determine the periods more accurately in 1620.  (Later astronomers overruled
Galileo's naming of these objects, changing his ''Medicean stars'' to
''Galilean satellites''.) The demonstration that a planet had smaller
planets orbiting it was problematic for the orderly, comprehensive
picture of the [[heliocentrism|geocentric model]] of the universe, in which
everything circled around the Earth.<ref>Galilei (1610); pp. 51&ndash;58</ref>


Galileo noted that [[Venus (planet)|Venus]] exhibited a full set of [[phase]]s like the [[Moon]]. Because the apparent brightness of Venus is nearly constant, Galileo reasoned that Venus could not be circling the Earth at a constant distance.  By contrast, the [[heliocentric model]] of the solar system developed by [[Copernicus]] would neatly account for the steady brightness by reason of the much greater distance from the Earth at the time of "full Venus", when the two planets were on opposite sides of the sun such that Venus' illuminated hemisphere faced the Earth.
Galileo noted that [[Venus (planet)|Venus]] exhibited a full set of
[[phase]]s like the [[Moon]]. This would be impossible if both Venus and the Sun
were in orbit around the Earth, but follows logically if both planets orbit the Sun. (It
is also consistent with the system of [[Tycho Brahe]] in which planets orbit the Sun, which orbits the Earth.)


Galileo was one of the first Europeans to observe [[sunspot]]s, although there is evidence that [[China|Chinese]] astronomers had done so before.  The very existence of sunspots showed another difficulty with the perfection of the heavens as assumed in the older philosophy.  And the annual variations in their motions, first noticed by Francesco Sizzi, presented great difficulties for either the geocentric system or that of [[Tycho Brahe]]. A dispute over priority in the discovery of sunspots led to a long and bitter feud with [[Christoph Scheiner]]; in fact, there can be little doubt that both of them were beaten by [[David Fabricius]] and his son Johannes.
Galileo made some of the earliest observations of [[sunspot]]s, although not the very first.
A dispute over priority in the discovery of sunspots led to a long and
bitter feud with [[Christoph Scheiner]]; in fact, there can be little
doubt that both of them were beaten by [[David Fabricius]] and his son
Johannes. And even before that, there were Chinese reports of sunspots. Galileo and Scheiner, however, were the first to make and record systematic observations, concluding, for instance, Galileo that the Sun rotates on its axis.  


He was the first to report lunar [[mountain]]s, whose existence he deduced from the patterns of light and shadow on the Moon's surface. He even estimated their 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", and not a perfect [[sphere]] as [[Aristotle]] had claimed.
Blemishes on the Sun were another observation that was repugnant to the philosophy of the time. And the
 
annual variations in the motions of the spots, first pointed out to Galileo by Francesco Sizzi,
Galileo observed [[Neptune (planet)|Neptune]] in [[1611]]; it appears in his notebooks as one of many dim stars which he saw with the telescope and did not particularly note.
presented great difficulties for either the geocentric system or that
of Tycho Brahe.


== Physics ==
== Physics ==


Galileo's theoretical and experimental work on the motions of bodies, along with the largely independent work of [[Johannes Kepler|Kepler]] and [[Ren&eacute; Descartes|Descartes]], was a precursor of the [[Classical mechanics]] developed by [[Isaac Newton|Sir Isaac Newton]].  He was a pioneer, at least in the European tradition, in performing rigorous experiments and insisting on a [[mathematics|mathematical]] description of the laws of nature.
One of the most famous stories about Galileo is that he dropped [[ball]]s of different [[Mass|masses]] from the [[Leaning Tower of Pisa]] to demonstrate that their [[velocity]] 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 Viviani, it is now not generally believed to be true. However, Galileo did do [[experiment]]s involving balls rolling down [[inclined plane]]s, which showed the same thing. He determined the correct mathematical law for acceleration: the total distance covered, starting from rest, is proportional to the square of the time.  He concluded that falling objects are [[acceleration|accelerated]] independently of their mass, and that objects retain their velocity unless a [[force]] acts upon them.
Galileo also noted that a [[pendulum]]'s swings always take the same amount of time, independently of the [[amplitude]].  While Galileo believed this equality of period to be exact, it is only approximate, applying to small swings.  It is good enough to regulate a [[clock]], however, as Galileo may have been the first to realize. (See [[#Technology|Technology]].)


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.
==Other sciences==


==Mathematics==
While Galileo's application of mathematics to experimental physics was
innovative, his mathematical methods were the standard ones of the day.
The analyses and proofs relied heavily on the [[Eudoxus|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 [[Niccolo Fontana Tartaglia|Tartaglia]] and others;
but by the end of Galileo's life it
was being superseded by the [[algebra|algebraic]] methods of [[René Descartes|Descartes]].


While Galileo's application of mathematics to experimental physics was innovative, his mathematical methods were the standard ones of the day. The analyses and proofs relied heavily on the [[Eudoxus of Cnidus|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 [[Niccolo Fontana Tartaglia|Tartaglia]] and others; but by the end of Galileo's life it was being superseded by the algebraic methods of [[René Descartes|Descartes]], which a modern finds incomparably easier to follow.
Galileo produced one piece of original and even prophetic work in
mathematics: [[Galileo's paradox]], which shows that there are as many
odd numbers as there are whole numbers including both even and odd.
Such seeming contradictions were brought under control 250 years later
in the work of [[Georg Cantor]].


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]].
In biology Galileo contributed what is probably the earliest quantitative law, the
[[Square-cube law]]. This law, part of his work on the strength of structures in [[Two New Sciences]], states that
the weight of a structure increases with the cube of the size when it is scaled up, while the strength of its supporting members increases only as the square. Hence, a large organism (like any other structure) will collapse of its own weight if simply made larger without change in its shape.<ref>Galilei (1638); pp. 126&ndash;128</ref>


== Technology ==
== Technology ==


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 Fontana Tartaglia|Tartaglia]] and Guidobaldo.  For gunners, it offered, in addition to a new and safer way of elevating cannon 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 [[Timeline of temperature and pressure measurement technology|earlier]]) Galileo made a [[thermometer]], using the expansion and contraction of air in a bulb to move water in an attached tube. 
In [[1610]] he used a telescope as a compound [[microscope]], and he made improved microscopes in [[1623]] and after.  This appears to be the [[Timeline of microscope technology|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 rest of his life; but the practical problems were severe. The method was first successfully applied by [[Giovanni Cassini|Cassini]] in [[1681]] and was later used extensively for land surveys; for navigation, the first practical method was the [[chronometer]] 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|Huygens]] in the 1650s. 
He created [[sketch]]es of various [[invention]]s, 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 ==
Galileo was a devout [[Catholicism|Catholic]], yet his writings on  [[Copernicus|Copernican]] [[heliocentric model|heliocentrism]] disturbed some in the [[Catholic Church]], who believed in a [[geocentric model]] of the [[solar system]]. They argued that heliocentrism was in direct contradiction of the [[Bible]] (which is a questionable claim) and the highly revered ancient writings of [[Aristotle]] and [[Plato]]. For his insights, Galileo was threatened with death at the stake and would eventually face lifelong house arrest after recanting his claims.
The geocentric model was generally accepted at the time for several reasons. By the time of the controversy, the Catholic Church had largely abandoned the Ptolemaic model for the [[Tycho Brahe|Tychonian]] model in which the Earth was at the centre of the [[Universe]], the [[Sun]] revolved around the Earth and the other planets revolved around the Sun. This model is geometrically equivalent to the Copernican model and had the extra advantage that it predicted no [[parallax]] of the stars, an effect that was impossible to detect with the instruments of the time. In the view of Tycho and many others, this model explained the observable data of the time better than the geocentric model did. (That inference is valid, however, only on the assumption that no very small effect had been missed: that the instruments of the time were absolutely perfect, or that the Universe ''could'' not be much larger than was generally believed at the time. As to the latter, belief in the large, possibly infinite, size of the Universe was part of the heretical beliefs for which [[Giordano Bruno]] had been burned at the stake in [[1600]].)
An understanding of the controversies, if it is even possible, requires attention not only to the politics of religious organizations but to those of academic philosophy.  Before Galileo had trouble with the Jesuits and before the Dominican friar Caccini denounced him from the pulpit, his employer heard him accused of contradicting Scripture by a professor of philosophy, Cosimo Boscaglia, who was neither a theologian nor a priest.  The first to defend Galileo was a Benedictine abbot, Benedetto Castelli, who was also a professor of mathematics and a former student of Galileo's.  It was this exchange that led Galileo to write the ''[[Letter to Grand Duchess Christina]]''.  (Castelli remained Galileo's friend, visiting him at Arcetri near the end of Galileo's life, after months of effort to get permission from the Inquisition to do so.)
However, real power lay with the Church, and Galileo's arguments were most fiercely fought on the [[religion|religious]] level. The late nineteenth and early twentieth century historian [[Andrew Dickson White]] wrote from an anti-clerical perspective:
<BLOCKQUOTE>
The war became more and more bitter. The Dominican Father Caccini preached a sermon from the text, "Ye men of Galilee, why stand ye gazing up into heaven?" and this wretched [[pun]] upon the great astronomer's name ushered in sharper weapons; for, before Caccini ended, he insisted that "geometry is of the devil," and that "mathematicians should be banished as the authors of all heresies." The Church authorities gave Caccini promotion.
Father Lorini proved that Galileo's doctrine was not only heretical but "atheistic," and besought the Inquisition to intervene. The Bishop of Fiesole screamed in rage against the Copernican system, publicly insulted Galileo, and denounced him to the Grand-Duke. The Archbishop of Pisa secretly sought to entrap Galileo and deliver him to the Inquisition at Rome. The Archbishop of Florence solemnly condemned the new doctrines as unscriptural; and Paul V, while petting Galileo, and inviting him as the greatest astronomer of the world to visit Rome, was secretly moving the Archbishop of Pisa to pick up evidence against the astronomer.
But by far the most terrible champion who now appeared was Cardinal [[Bellarmine |Bellarmin]], one of the greatest theologians the world has known. He was earnest, sincere, and learned, but insisted on making science conform to Scripture. The weapons which men of Bellarmin's stamp used were purely theological. They held up before the world the dreadful consequences which must result to Christian theology were the heavenly bodies proved to revolve about the Sun and not about the Earth. Their most tremendous dogmatic engine was the statement that "his pretended discovery vitiates the whole Christian plan of salvation." Father Lecazre declared "it casts suspicion on the doctrine of the incarnation." Others declared, "It upsets the whole basis of theology. If the Earth is a planet, and only one among several planets, it can not be that any such great things have been done specially for it as the Christian doctrine teaches. If there are other planets, since God makes nothing in vain, they must be inhabited; but how can their inhabitants be descended from Adam? How can they trace back their origin to Noah's ark? How can they have been redeemed by the Saviour?" Nor
was this argument confined to the theologians of the Roman Church; Melanchthon, Protestant as he was, had already used it in his attacks on Copernicus and his school. (White, 1898; [http://www.santafe.edu/~shalizi/White/astronomy/war.html online text])
</BLOCKQUOTE>
In [[1616]], the [[Inquisition]] warned Galileo not to hold or defend the hypothesis asserted in Copernicus's ''On the Revolutions'', though it has been debated whether he was admonished not to "teach in any way" the heliocentric theory.  When Galileo was tried in [[1633]], the Inquisition was proceeding on the premise that he had been ordered not to teach it at all, based on a paper in the records from 1616; but Galileo produced a letter from Cardinal Bellarmine that showed only the "hold or defend" order.  The latter is in Bellarmine's own hand and of unquestioned authenticity; the former is an unsigned copy, violating the Inquisition's own rule that the record of such an admonition had to be signed by all parties and notarized.  Leaving aside technical rules of evidence, what can one conclude as to the real events?  There are two schools of thought. According to Stillman Drake, the order not to teach was delivered unofficially and improperly; Bellarmine would not allow a formal record to be made, and assured Galileo in writing that the only order in effect was not to "defend or hold".  According to Giorgio di Santillana, however, the unsigned minute was simply a fabrication by the Inquisition.
Despite his continued insistence that his work in the area was purely theoretical, despite his strict following of the church protocol for publication of works (which required prior examination by church censors and subsequent permission), and despite his close friendship with Maffeo Barberini who later became [[Pope Urban VIII]] and presided throughout the ordeal, Galileo was forced to recant his views repeatedly, and was put under life-long house arrest from [[1633]] to [[1642]].
The [[Roman Inquisition]] had rejected earlier pleas by Galileo to postpone or relocate the [[trial]] because of his ill health. At a meeting presided by Pope Urban VIII, the Inquisition decided to notify Galileo that he either had to come to [[Rome]] or that he would be arrested and brought there in chains. Galileo arrived in Rome for his trial before the [[Inquisition]] on [[February 13]], [[1633]]. After two weeks in quarantine, Galileo was detained at the comfortable residence of the [[Tuscan ambassador]], as a favor to the influential Grand Duke [[Ferdinand II de' Medici]]. When the ambassador reported Galileo's arrival and asked how long the proceedings would be, the Pope replied that the Holy Office proceeded slowly, and was still in the process of preparing for the formal proceedings. In the event, having responded to the urgent demands of the Inquisition that he must report to Rome immediately, Galileo was laft to wait for two months before proceedings would begin.
On [[April 12]], [[1633]], Galileo was brought to trial, and the formal interrogation by the Inquisition began. During this interrogation Galileo stated that he did not defend the Copernican theory, and cited a letter of Cardinal Bellarmine from [[1615]] to support this contention. The Inquisition questioned him on whether he had been ordered in 1616 not to teach Copernican ideas in any way (see above); he denied remembering any such order, and produced a letter from Bellarmine saying only that he was not to hold or defend those doctrines.
He was then detained for eighteen days in a room in the offices of the Inquisition (not in a dungeon cell). During this time the Commissary General of the Inquisition, Vincenzo (later Cardinal) Maculano, visited him for what amounted to [[plea bargain]]ing, persuading Galileo to confess to having gone too far in writing the book. In a second hearing on [[April 30]], Galileo confessed to having erred in the writing of the book, through vain ambition, ignorance, and inadvertence. He was then allowed to return to the home of the Tuscan ambassador. On [[May 10]] he submitted his written defense, in which he defended himself against the charge of disobeying the Church's order, confessed to having erred through pride in writing the book, and asked for mercy in light of his age and ill health.
A month later ([[June 21]]), by order of the Pope, he was given an examination of intention, a formal process that involved showing the accused the instruments of torture. At this proceeding, he said, "I am here to obey, and have not held this [Copernican] opinion after the determination made, as I said."
On [[June 22]], [[1633]], the Inquisition held the final hearing on Galileo, who was then 69 years old and pleaded for mercy, pointing to his "regrettable state of physical unwellness". Threatening him with [[torture]], imprisonment, and death on the stake, the [[show trial]] forced Galileo to "abjure, curse and detest" his work and to promise to denounce others who held his prior viewpoint. Galileo did everything the church requested him to do, following (so far as we can tell) the plea bargain of two months earlier. He was convicted and sentenced to life imprisonment.


Although ten Cardinal Inquisitors had heard the case, the sentence carried out on June 22 bears the signature of only seven; one of the three missing was Cardinal Barberini, the Pope's nephew. It is generally held that this indicates a refusal to endorse the sentence. The seven who signed, however, were those who were present at that day's proceedings; Cardinals Barberini and Borgia in particular, were attending an audience with the Pope on that day. Analysis of the Inquisition's records has shown that the presence of only seven of ten Cardinals was not exceptional; hence the inference that Barberini was protesting the decision may be doubted.
==Relations with the Church==


That the threat of torture and death Galileo was facing was a real one had been proven by the church in the earlier trial against [[Giordano Bruno]], who was burned at the stake in [[1600]] for holding a naturalistic view of the Universe.
During the second half of his life Galileo, a practicing Catholic, had many problems with important figures in the Catholic Church, including a sainted Cardinal, members of the Inquisition, and two Popes. There were periods in which peace and good will prevailed, and Galileo had at all times many friends and supporters in the Church; but the outcome was a conflict that became legendary. Nearly every aspect of this conflict has been and remains the subject of controversy, often bitter. A relatively brief summary of the events and their historical background will be given here, followed by a more extensive treatment in several sections.


The tale that Galileo, rising from his knees after recanting, said "''Eppur si muove!''" (But it does move!) cannot possibly be true; to say any such thing in the offices of the Inquisition would have been a ticket to follow Bruno to the stake.  But the widespread belief that the whole incident is an 18th-century invention is also false.  A Spanish painting, dated 1643 or possibly 1645, shows Galileo writing the phrase on the wall of a dungeon cell. Here we have a second version of the story, which also cannot be true, because Galileo was never imprisoned in a dungeon; but the painting shows that some story of "Eppur si muove" was circulating in Galileo's time. In the months immediately after his condemnation, Galileo resided with Archbishop Ascanio Piccolomini of [[Siena]], a learned man and a sympathetic host; the fact that Piccolomini's brother was a military attach&eacute; in [[Madrid]], where the painting was made some years later, suggests that Galileo may have made the remark to the Archbishop, who then wrote to his family conerning the event, which later became garbled in re-telling.  
The [[Center of the world|heliocentric]] idea&mdash;that the Earth moves around the Sun, rather than the reverse&mdash;contradicts what is perfectly obvious to anyone who looks at the skies. Where the idea existed at all, it was often treated as irreligious; the Greek philosopher [[Aristarchus]], as a result of his advocacy of the idea, was accused of [[atheism]]. In Christian Europe the problem was aggravated by the perceived contradiction between heliocentrism and some passages in the Bible; moreover, heliocentrism was against the teachings of Aristotle, whose work was dominant among the learned and was the official basis of Catholic philosophy. When [[Copernicus]] first published his heliocentric system in 1543, it was considered a fairly obscure matter and raised little trouble; but in the next century it became the source of much conflict.


Galileo was sentenced to prison, but because of his advanced age (and/or Church politics) the sentence was commuted to house arrest at his villas in [[Arcetri]] and [[Florence]][http://www.lucidcafe.com/library/96feb/galileo.html].
After 1610 the discoveries that Galileo and others made using the telescope demonstrated that many of the accepted ideas of astronomy were factually wrong. These findings made heliocentrism more plausible and in some ways provided direct support for it, though not rigorous proof. Galileo began publicly arguing for heliocentrism at this time and was promptly attacked on religious grounds&mdash;by philosophers as well as clerics. (There was also scientific controversy; his main argument for heliocentrism is in fact wrong, while he rejected Kepler's cogent point. On both scientific and religious grounds Galileo had many supporters, both within and outside the Church.) Hostile responses ranged from a fiery sermon on the text, "Ye men of Galilee, why stand ye gazing up into
Because of a painful [[hernia]], he requested permission to consult physicians in Florence, which was denied by Rome, which warned that further such requests would lead to imprisonment. Under arrest, he was forced to recite penitentiary [[psalm]]s regularly, and his social contacts were at times highly restricted, but he was allowed to continue his less controversial research.
heaven?"<ref>Acts 1:11 http://www.biblegateway.com/passage/?search=Acts%201:11;&version=9;</ref> to direct complaints to the Inquisition. Such attacks were serious, potentially backed by the power of the Church to enforce doctrine.


Publication was another matter. His ''Dialogue'' had been put on the ''[[Index Librorum Prohibitorum]]'', the official black list of banned books, where it stayed until [[1822]] (Hellman, 1998).  Though the sentence announced against Galileo mentioned no other works, Galileo found out two years later that publication of anything he might ever write had been quietly banned.  The ban was effective in France, Poland, and German states, but not in the Netherlands.
In 1616 Galileo went to Rome to argue against the banning of Copernican teachings. This mission (often called the first trial of Galileo, although it was not a trial in any formal sense) was a failure. In the end, the heliocentric works of Copernicus and others were temporarily suppressed pending theological "corrections"; a book by the priest [[Paolo Antonio Foscarini]], arguing that heliocentrism was not in conflict with Christianity, was formally banned; and Galileo was directly ordered not to "hold or defend" the Copernican ideas.  


He went totally [[blindness|blind]] in [[1638]] (his petition to the Inquisition to be released was rejected, but he was allowed to move to his house in Florence where he was closer to his physicians).
Until 1624 Galileo avoided any dangerous public involvement with heliocentrism. In that year the new Pope, [[Urban VIII]], who was an admirer of Galileo's work, approved his writing a book about the theory, on condition that it would not argue that Copernican ideas were true, but merely give both sides. Galileo necessarily accepted the condition, but it is clear that the resulting work is not neutral, but takes the Copernican side.


According to Andrew Dickson White and many of his colleagues, Galileo's experiences demonstrate a classic case of a scholar forced to recant a scientific insight because it offended powerful, conservative forces in society: for the church at the time, it was not the [[scientific method]] that should be used to find truth -- especially in certain areas -- but the doctrine as interpreted and defined by church scholars, and this doctrine was defended with torture, murder, deprivation of freedom, and [[censorship]].
In 1630 Galileo completed the book, the ''[[Dialogue Concerning the Two Chief World Systems]]'', and submitted it to the [[Congregation of the Index]] for approval to publish. The process was long and difficult and required changes to the book before the license could be issued. When finally published in 1632, the book immediately encountered determined opposition. Galileo was ordered to go to Rome to be questioned by the authorities. In 1633 he was tried by the Inquisition on "grave suspicion of heresy" and on charges that he had disobeyed the orders given him in 1616. He was convicted, forced to recant his ideas, and placed under permanent house arrest. (The story of his saying "But it does move!" refers to this proceeding.) His ''Dialogue'' was banned, and somewhat later all his works were banned.  


More recently, the viewpoints of White and his colleagues have become less generally accepted by the academic community, partially because White wrote from a perspective that Christianity is a destructive force. This attitude can also be seen in the works of [[Bertolt Brecht]], whose play about Galileo is one of the chief sources for popular ideas about the scientist. Moreover, deeper examination of the primary sources for Galileo and his trial shows that claims of torture and deprivation were likely exaggerated. [[Dava Sobel]]'s ''[[Galileo's Daughter]]'' offers a different set of insights into Galileo and his world, in large part through the private correspondence of Maria Celeste, the daughter of the title, and her father.
The suppression of heliocentric books began to be relaxed in 1741, and was finally completely removed in 1822. In 1994 Pope [[John Paul II]] issued a formal statement that cleared Galileo of the taint of heresy. The Pope's position, though widely accepted and welcomed, is now the occasion for some controversy, even within the Church.


In [[1992]], 359 years after the Galileo trial, [[Pope John Paul II]] issued an apology, lifting the edict of Inquisition against Galileo: "Galileo sensed in his scientific research the presence of the Creator who, stirring in the depths of his spirit, stimulated him, anticipating and assisting his intuitions."  After the release of this report, the Pope said further that "... Galileo, a sincere believer, showed himself to be more perceptive in this regard [the relation of scientific and Biblical truths] than the theologians who opposed him."
===Opening of the controversy===


== Writings by Galileo ==
===First meetings with theological authorities===


* ''[[Dialogue Concerning the Two Chief World Systems]]''
===The Dialogue===


* ''[[Two New Sciences]]''
===The trial===


* ''[[Sidereus Nuncius|The Starry (Sidereal) Messenger]]''
===Aftermath===


* ''[[Letter to Grand Duchess Christina]]''
==Notes and references==
<references/>


''See also:'' [[Galilean transformation]], [[Lorentz transformation equations]]
===Works cited===


== References ==
* Drake, Stillman (1957). ''Discoveries and Opinions of Galileo''. New York: Doubleday & Company. ISBN 0-385-09239-3
 
* Drake, Stillman (1973). "Galileo's Discovery of the Law of Free Fall". ''Scientific American'' v. 228, #5, pp. 84-92.
* Drake, Stillman (1978). ''Galileo At Work''. Chicago: University of Chicago Press. ISBN 0-226-16226-5
* Drake, Stillman (1978). ''Galileo At Work''. Chicago: University of Chicago Press. ISBN 0-226-16226-5
* Fantoli, Annibale (2003). ''Galileo&mdash;For Copernicanism and the Church'', third English edition. Vatican Observatory Publications. ISBN 88-209-7427-4
* Fantoli, Annibale (2003). ''Galileo &mdash; For Copernicanism and the Church'', third English edition. Vatican Observatory Publications. ISBN 88-209-7427-4
* Hellman, Hal (1988). ''Great Feuds in Science. Ten of the Liveliest Disputes Ever''. New York: Wiley.
* Galilei, Galileo (1610). ''The Starry Messenger'' (''Sidereus Nuncius''). In Drake (1957):22-58
* Settle, Thomas B. (1961). "An Experiment in the History of Science". ''Science'',  133:19-23.
* Galilei, Galileo (1638). ''Two New Sciences'' (''tr.'' Stillman Drake). Madison: University of Wisconsin Press (1974). ISBN 0-299-06400[[Category:Suggestion Bot Tag]]
* White, Andrew Dickson (1898). ''A History of the Warfare of Science with Theology in Christendom''. New York 1898. Public domain text, [http://www.santafe.edu/~shalizi/White/ full online version].
 
== External links ==
 
* [http://quote.wikipedia.org/wiki/Galileo_Galilei Galileo quote collection] at [[Wikiquote]]
* [http://www.infidels.org/library/historical/andrew_white/Chapter3.html The Warfare of Science With Theology]
* [http://es.rice.edu/ES/humsoc/Galileo/ The Galileo Project] at [[Rice University]]
* [http://www.mpiwg-berlin.mpg.de/Galileo_Prototype/MAIN.HTM Electronic representation of Galilei's notes on motion (MS. 72)]
* [http://www.firstthings.com/ftissues/ft0401/reviews/barr.html From Myth to History and Back] - Reviews of two books on Galileo
 
[[Category:Astronomy Workgroup]]

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Galileo Galilei (1564-1642) was an Italian scientist who was a major figure in the Scientific Revolution. He was a pioneer in the modern combination of mathematical theory with systematic experiment in science.

His work in physics included experimentation to establish the behavior of falling bodies, as well as the first modern theoretical work on inertia (for which he was given credit by Newton) and relativity of motion (for which he was credited by Einstein).

He was one of the first astronomers to use a telescope, and the discoverer or co-discoverer of several phenomena that contradicted the accepted ideas of the heavens. His support of the Copernican idea that the Earth revolves around the Sun led to a trial before the Inquisition on a suspicion of heresy.

Experimental science

Among the figures of the scientific revolution Galileo occupies 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, the musician Vincenzo Galilei, 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.)

In the 20th century the reality of Galileo's experiments was challenged by some authorities, in particular the distinguished French historian of science Alexandre Koyré. 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 have been impossible with the technology of 1600. According to Koyré, the law was arrived at deductively, and Galileo's experiments, reported in some detail as if actually performed, were merely illustrative thought experiments.

Later research, however, has validated the experiments. The measurements on falling bodies (actually rolling balls) were replicated using the methods described by Galileo,[1] and the precision of the results was consistent with Galileo's report. Later research into Galileo's unpublished working papers from as early as 1604 clearly showed the reality of the experiments and even indicated the particular results that led to the time-squared law.[2]

Astronomy

In July of 1609 Galileo heard a report that a traveler from Flanders had shown "a glass by means of which distant objects could be seen as distinctly as if they were nearby." This person or another traveler then negotiated with the government of Venice to sell his secret device at a high price. A telescope had in fact been the subject of a patent application the previous year by Hans Lippershey, a Dutch spectacle maker, and had been known for months to Galileo's friend Paolo Sarpi. (Compare the story, found not only in Brecht's play "Galileo" but in some authors claiming to give a historical account,[3] that Galileo attempted to claim full credit for the invention of the telescope.) Without seeing the telescope, Galileo soon figured out how to make a crude one, which was followed by series of improvements, including an 8-power telescope and one of 20 power, probably in November of 1609.[4]

Before the start of 1610 Galileo was using his telescopes to observe the Moon and stars.[5] He soon saw that the line of shadow separating the light and dark sides of the moon (the terminator) was highly irregular and moved in an irregular fashion, leading to the conclusion that the surface was rough, contrary to the unanimous belief at that time that all heavenly bodies were perfectly spherical and smooth. By measuring shadows he estimated the height of lunar mountains with reasonable accuracy, and noted that they seemed to be higher than terrestrial ones.[6]

In January 1610 Galileo discovered Jupiter's four largest satellites (moons): Io, Europa, Ganymede, and Callisto. Over the succeeding months he was able to determine the orbital periods of the satellites, and he made additional observations to determine the periods more accurately in 1620. (Later astronomers overruled Galileo's naming of these objects, changing his Medicean stars 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.[7]

Galileo noted that Venus exhibited a full set of phases like the Moon. This would be impossible if both Venus and the Sun were in orbit around the Earth, but follows logically if both planets orbit the Sun. (It is also consistent with the system of Tycho Brahe in which planets orbit the Sun, which orbits the Earth.)

Galileo made some of the earliest observations of sunspots, although not the very first. A dispute over priority in the discovery of sunspots led to a long and bitter feud with Christoph Scheiner; in fact, there can be little doubt that both of them were beaten by David Fabricius and his son Johannes. And even before that, there were Chinese reports of sunspots. Galileo and Scheiner, however, were the first to make and record systematic observations, concluding, for instance, Galileo that the Sun rotates on its axis.

Blemishes on the Sun were another observation that was repugnant to the philosophy of the time. And the annual variations in the motions of the spots, first pointed out to Galileo by Francesco Sizzi, presented great difficulties for either the geocentric system or that of Tycho Brahe.

Physics

Other sciences

While Galileo's application of mathematics to experimental physics was innovative, his mathematical methods were the standard ones of the day. The analyses 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 odd numbers as there are whole numbers including both even and odd. Such seeming contradictions were brought under control 250 years later in the work of Georg Cantor.

In biology Galileo contributed what is probably the earliest quantitative law, the Square-cube law. This law, part of his work on the strength of structures in Two New Sciences, states that the weight of a structure increases with the cube of the size when it is scaled up, while the strength of its supporting members increases only as the square. Hence, a large organism (like any other structure) will collapse of its own weight if simply made larger without change in its shape.[8]

Technology

Relations with the Church

During the second half of his life Galileo, a practicing Catholic, had many problems with important figures in the Catholic Church, including a sainted Cardinal, members of the Inquisition, and two Popes. There were periods in which peace and good will prevailed, and Galileo had at all times many friends and supporters in the Church; but the outcome was a conflict that became legendary. Nearly every aspect of this conflict has been and remains the subject of controversy, often bitter. A relatively brief summary of the events and their historical background will be given here, followed by a more extensive treatment in several sections.

The heliocentric idea—that the Earth moves around the Sun, rather than the reverse—contradicts what is perfectly obvious to anyone who looks at the skies. Where the idea existed at all, it was often treated as irreligious; the Greek philosopher Aristarchus, as a result of his advocacy of the idea, was accused of atheism. In Christian Europe the problem was aggravated by the perceived contradiction between heliocentrism and some passages in the Bible; moreover, heliocentrism was against the teachings of Aristotle, whose work was dominant among the learned and was the official basis of Catholic philosophy. When Copernicus first published his heliocentric system in 1543, it was considered a fairly obscure matter and raised little trouble; but in the next century it became the source of much conflict.

After 1610 the discoveries that Galileo and others made using the telescope demonstrated that many of the accepted ideas of astronomy were factually wrong. These findings made heliocentrism more plausible and in some ways provided direct support for it, though not rigorous proof. Galileo began publicly arguing for heliocentrism at this time and was promptly attacked on religious grounds—by philosophers as well as clerics. (There was also scientific controversy; his main argument for heliocentrism is in fact wrong, while he rejected Kepler's cogent point. On both scientific and religious grounds Galileo had many supporters, both within and outside the Church.) Hostile responses ranged from a fiery sermon on the text, "Ye men of Galilee, why stand ye gazing up into heaven?"[9] to direct complaints to the Inquisition. Such attacks were serious, potentially backed by the power of the Church to enforce doctrine.

In 1616 Galileo went to Rome to argue against the banning of Copernican teachings. This mission (often called the first trial of Galileo, although it was not a trial in any formal sense) was a failure. In the end, the heliocentric works of Copernicus and others were temporarily suppressed pending theological "corrections"; a book by the priest Paolo Antonio Foscarini, arguing that heliocentrism was not in conflict with Christianity, was formally banned; and Galileo was directly ordered not to "hold or defend" the Copernican ideas.

Until 1624 Galileo avoided any dangerous public involvement with heliocentrism. In that year the new Pope, Urban VIII, who was an admirer of Galileo's work, approved his writing a book about the theory, on condition that it would not argue that Copernican ideas were true, but merely give both sides. Galileo necessarily accepted the condition, but it is clear that the resulting work is not neutral, but takes the Copernican side.

In 1630 Galileo completed the book, the Dialogue Concerning the Two Chief World Systems, and submitted it to the Congregation of the Index for approval to publish. The process was long and difficult and required changes to the book before the license could be issued. When finally published in 1632, the book immediately encountered determined opposition. Galileo was ordered to go to Rome to be questioned by the authorities. In 1633 he was tried by the Inquisition on "grave suspicion of heresy" and on charges that he had disobeyed the orders given him in 1616. He was convicted, forced to recant his ideas, and placed under permanent house arrest. (The story of his saying "But it does move!" refers to this proceeding.) His Dialogue was banned, and somewhat later all his works were banned.

The suppression of heliocentric books began to be relaxed in 1741, and was finally completely removed in 1822. In 1994 Pope John Paul II issued a formal statement that cleared Galileo of the taint of heresy. The Pope's position, though widely accepted and welcomed, is now the occasion for some controversy, even within the Church.

Opening of the controversy

First meetings with theological authorities

The Dialogue

The trial

Aftermath

Notes and references

  1. ↑ Settle, Thomas B. (1961). "An Experiment in the History of Science". Science, 133:19-23.
  2. ↑ Drake, Stillman (1973). "Galileo's Discovery of the Law of Free Fall". Scientific American v. 228, #5: 84-92
  3. ↑ http://www.catholiceducation.org/articles/history/world/wh0005.html
  4. ↑ Drake (1978); pp. 137–143
  5. ↑ Note: Year 2009 marks the 400th anniversary of Galileo's first use of the telescope, which enabled his revolutionizing astronomy. It also marks the 200th anniversary of Charles Darwin's birth, enabling his revolution of biology.
  6. ↑ Galilei (1610); pp. 32–41
  7. ↑ Galilei (1610); pp. 51–58
  8. ↑ Galilei (1638); pp. 126–128
  9. ↑ Acts 1:11 http://www.biblegateway.com/passage/?search=Acts%201:11;&version=9;

Works cited

  • Drake, Stillman (1957). Discoveries and Opinions of Galileo. New York: Doubleday & Company. ISBN 0-385-09239-3
  • Drake, Stillman (1978). Galileo At Work. Chicago: University of Chicago Press. ISBN 0-226-16226-5
  • Fantoli, Annibale (2003). Galileo — For Copernicanism and the Church, third English edition. Vatican Observatory Publications. ISBN 88-209-7427-4
  • Galilei, Galileo (1610). The Starry Messenger (Sidereus Nuncius). In Drake (1957):22-58
  • Galilei, Galileo (1638). Two New Sciences (tr. Stillman Drake). Madison: University of Wisconsin Press (1974). ISBN 0-299-06400
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