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Galileo Galilei

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Galileo Galilei (February 15, 1564 - January 8, 1642), was an Italian astronomer, philosopher,physicist whoclosely associated withScientific Revolution. He has been referredas"fathermodern astronomy" (a titlewhich Kepler has perhapsstronger claim), as"fathermodern physics",as "fatherscience". His experimental workwidely considered complementary towritingsBaconestablishingmodern scientific method. Galileo was bornPisahis career coincidedthatKepler. The workGalileoconsideredbesignificant break from thatAristotle;particular, Galileo placed emphasis on quantity, rather than quality.

Tablecontents
1 Experimental science
2 Astronomy
3 Physics
4 Mathematics
5 Technology
6 Church controversy
7 Writings by Galileo
8 References
9 External links

Experimental science

Inpantheon ofscientific revolution Galileo occupies a high position becausehis pioneering usequantitative experiments with results analyzed mathematically. There was no traditionsuch methods in European thought at that time;great experimentalist who immediately preceded Galileo, William Gilbert, did not usequantitative approach. (However, Galileo's father, Vincenzo Galilei, had performed experimentswhich he discovered what may beoldest known non-linear relationphysics, betweentension andpitch ofstretched string.)

In20th centuryrealityGalileo's experiments was challenged by some authorities,particulardistinguished French historianscience Alexandre Koyré. The experiments reportedTwo New Sciencesdeterminelawaccelerationfalling bodies,instance, required accurate measurementstime, which appearedhave been impossible withtechnology1600. AccordingKoyré,law was arrived at deductively, andexperiments were merely illustrative thought experiments.

Later research, however, has validatedexperiments. The experiments on falling bodies (actually rolling balls) were replicated usingmethods described by Galileo (Settle, 1961), andprecision ofresults was consistentGalileo's report. Later research into Galileo's unpublished working papers from as early as 1604 clearly showedreality ofexperimentseven indicatedparticular results that led totime-squared law (Drake, 1973).

Astronomy

Galileo was one offirst peopleusetelescopeobservesky. Based on sketchy descriptionsexisting telescopes, he made oneabout 8x magnification,then made improved models upabout 20x. He published his initial telescopic observationsMarch 1610 inshort treatise entitled Sidereus Nuncius (Sidereal Messenger).

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Galileo Galilei’s discovery ofmoonsJupiter. This ismanuscript page,Italian, on which Galileo first noted an observation ofmoons;full descriptionthem appearedSidereus NunciusMarch 1610.
Fortranslation from Sidereus Nuncius click onpicture.
Larger version

In 1610 Galileo discovered Jupiter's four largest satellitess (moons): Io, Europa, Ganymede,Callisto. He determined that these moons were orbitingplanet sincewould occasionally disappear; something he attributedtheir movement behind Jupiter. He made additional observationsthem1620. (Later astronomers overruled Galileo's namingthese objects, changing his Medicean starsGalilean satellites.) The demonstration thatplanet had smaller planets orbitingwas problematic fororderly, comprehensive picture ofgeocentric model ofuniverse,which everything circled aroundEarth.

Galileo noted that Venus exhibitedfull setphases likeMoon. Becauseapparent brightnessVenusnearly constant, Galileo reasoned that Venus could not be circlingEarth atconstant distance. By contrast,heliocentric model ofsolar system developed by Copernicus would neatly account forsteady brightness by reason ofmuch greater distance fromEarth attime"full Venus", whentwo planets were on opposite sides ofsun such that Venus' illuminated hemisphere facedEarth.

Galileo madefirst European observationssunspots, although thereevidence that Chinese astronomers had done so before him. The very existencesunspots showed another difficulty withperfection ofheavens as assumed inolder philosophy. Andannual variationstheir motions, first noticed by Francesco Sizzi, presented great difficultieseithergeocentric system or thatTycho Brahe.

He wasfirstreport lunar mountains, whose existence he deduced frompatternslightshadow onMoon's surface. He even estimated their heights from these observations. This led him toconclusion thatMoon was "roughuneven,just likesurface ofEarth itself",notperfect sphere as Aristotle had claimed.

Galileo observed Neptune1611, but believed itbestar.

Physics

Galileo's theoreticalexperimental work onmotionsbodies, along withlargely independent workKeplerDescartes, wasprecursor ofClassical mechanics developed by Sir Isaac Newton. He waspioneer, at least inEuropean tradition,performing rigorous experimentsinsisting onmathematical description oflawsnature.

One ofmost famous stories about Galileothat he dropped ballsdifferent masses fromLeaning TowerPisademonstrate that their velocitydescent was independenttheir mass (excludinglimited effectair resistance). This was contrarywhat Aristotle had taught: that heavy objects fall faster than lighter ones,direct proportionweight. Thoughstory oftower first appeared inbiography by Galileo's pupil Viviani, itnow not generally believedbe true. However, Galileo did do experiments involving balls rolling down inclined planes, which showedsame thing. He determinedcorrect mathematical lawacceleration:total distance covered, starting from rest,proportional tosquare oftime. He concluded that falling objectsaccelerated independentlytheir mass,that objects retain their velocity unlessforce acts upon them.

Galileo also noted thatpendulum's swings always takesame amounttime, independently ofamplitude. While Galileo believed this equalityperiodbe exact, itonly approximate, applyingsmall swings. Itgood enoughregulateclock, however, as Galileo may have beenfirstrealize. (See Technology.)

Inearly 1600s, Galileoan assistant triedmeasurespeedlight. They stood on different hilltops, each holdingshuttered lantern. Galileo would open his shutter, and, as soon as his assistant sawflash, he would open his shutter. Atdistanceless thanmile, Galileo could detect no delay inround-trip time greater than when he andassistant were onlyfew yards apart. While he could reach no conclusion on whether light propagated instantaneously, he recognized thatdistance betweenhilltops was perhaps too small forgood measurement.

Mathematics

While Galileo's applicationmathematicsexperimental physics was innovative, his mathematical methods werestandard ones ofday. The analysesproofs relied heavily onEudoxian theoryproportion, as set forth infifth bookEuclid's Elements. This theory had become available onlycentury before, thanksaccurate translations by Tartagliaothers; but byendGalileo's lifewas being superseded byalgebraic methodsDescartes, whichmodern finds incomparably easierfollow.

Galileo produced one pieceoriginaleven prophetic workmathematics: Galileo's paradox, which shows that thereas many perfect squares as therewhole numbers, even though most numbersnot perfect squares. Such seeming contradictions were brought under control 250 years later inworkGeorg Cantor.

Technology

Galileo madefew contributionswhat we now call technology as distinct from pure physics,suggested others. Thisnotsame distinction as made by Aristotle, who would have considered all Galileo's physics as techne or useful knowledge, as opposedepisteme, or philosophical investigation intocausesthings.

In 1595 - 1598 Galileo devisedimproved"GeometricMilitary Compass" suitableuse by gunnerssurveyors. This expanded on earlier instruments designed by TartagliaGuidobaldo. For gunners,offered,addition tonewsafer wayelevating cannon accurately,wayquickly computingchargegunpowdercannonballsdifferent sizesmaterials. Asgeometric instrumentenabledconstructionany regular polygon, computation ofareaany polygon or circular sector, andvarietyother calculations.

About 1606 - 1607 (or possibly earlier) Galileo madethermometer, usingexpansioncontractionair inbulbmove wateran attached tube.

In 1610 he usedtelescope ascompound microscope,he made improved microscopes1623after. This appearsbefirst clearly documented use ofcompound microscope.

In 1612, having determinedorbital periodsJupiter's satellites, Galileo proposed thatsufficiently accurate knowledgetheir orbits one could use their positions asuniversal clock,this would make possibledeterminationlongitude. He worked on this problem from timetime duringresthis life; butpractical problems were insurmountable,it was another century before John Harrison mastered longitudehis chronometer.

In his last year, when totally blind, he designed an escapement mechanism forpendulum clock. The first fully operational pendulum clock was made by Huygens in1650s.

He created sketchesvarious inventions, such ascandlemirror combinationreflect light throughoutbuilding, an automatic tomato picker,pocket comb that doubled as an eating utensil,what appearsbeballpoint pen.

Church controversy

Galileo wasdevout Catholic, yet his writings on Copernican heliocentrism disturbedCatholic Church, which believed ingeocentric model ofsolar system. The church argued that heliocentrism wasdirect contradiction ofBible andhighly revered ancient writingsAristotlePlato. For his insights, Galileo was threateneddeath atstakewould eventually face lifelong house arrest after recanting his claims.

The geocentric model was generally accepted attime not onlyscriptural reasons. Bytime ofcontroversy,Catholic Church hadfact abandonedPtolemaic model forTychonian modelwhichEarth was atcentre ofUniverse,Sun revolved aroundEarth andother planets revolved aroundSun. This modelgeometrically equivalent toCopernican modelhadextra advantage thatpredicted no parallax ofstars, an effect that we now know was impossibledetect withinstruments oftime.

An understanding ofcontroversies, if iteven possible, requires attention not only topoliticsreligious organizations butthoseacademic philosophy. Before Galileo had trouble withJesuitsbeforeDominican friar Caccini denounced him frompulpit, his employer heard him accusedcontradicting Scripture byprofessorphilosophy, Cosimo Boscaglia, who was neithertheologian norpriest. The firstdefend Galileo wasBenedictine abbot, Benedetto Castelli, who was alsoprofessormathematics andformer studentGalileo's. It was this exchange that led GalileowriteLetterGrand Duchess Christina. (Castelli remained Galileo's friend, visiting him at Arcetri nearendGalileo's life, after monthseffortget permission fromInquisitiondo so.)

However, real power lay withChurch,Galileo's arguments were most fiercely fought onreligious level. The late nineteenthearly twentieth century historian Andrew Dickson White wrote from an anti-clerical perspective:

The war became moremore bitter. The Dominican Father Caccini preachedsermon fromtext, "Ye menGalilee, why stand ye gazing up into heaven?"this wretched pun upongreat astronomer's name usheredsharper weapons; for, before Caccini ended, he insisted that "geometryofdevil,"that "mathematicians should be banished asauthorsall heresies." The Church authorities gave Caccini promotion.

Father Lorini proved that Galileo's doctrine was not only heretical but "atheistic,"besoughtInquisitionintervene. The BishopFiesole screamedrage againstCopernican system, publicly insulted Galileo,denounced him toGrand-Duke. The ArchbishopPisa secretly soughtentrap Galileodeliver him toInquisition at Rome. The ArchbishopFlorence solemnly condemnednew doctrines as unscriptural;Paul V, while petting Galileo,inviting him asgreatest astronomer ofworldvisit Rome, was secretly movingArchbishopPisapick up evidence againstastronomer.

But by farmost terrible champion who now appeared was Cardinal Bellarmin, one ofgreatest theologiansworld has known. He was earnest, sincere,learned, but insisted on making science conformScripture. The weapons which menBellarmin's stamp used were purely theological. They held up beforeworlddreadful consequences which must resultChristian theology wereheavenly bodies provedrevolve aboutSunnot aboutEarth. Their most tremendous dogmatic engine wasstatement that "his pretended discovery vitiateswhole Christian plansalvation." Father Lecazre declared "it casts suspicion ondoctrine ofincarnation." Others declared, "It upsetswhole basistheology. IfEarth isplanet,only one among several planets,can not be that any such great things have been done speciallyit asChristian doctrine teaches. If thereother planets, since God makes nothingvain,must be inhabited; but how can their inhabitants be descended from Adam? How cantrace back their originNoah's ark? How canhave been redeemed bySaviour?" Nor was this argument confined totheologians ofRoman Church; Melanchthon, Protestant as he was, had already usedin his attacks on Copernicushis school. (White, 1898; online text)

In 1616,Inquisition warned Galileo nothold or defendhypothesis assertedCopernicus's OnRevolutions, thoughhas been debated whether he was admonished not"teachany way"heliocentric theory. When Galileo was tried1633,Inquisition was proceeding onpremise that he had been ordered notteachat all, based onpaper inrecords from 1616; but Galileo producedletter from Cardinal Bellarmine that showed only"hold or defend" order. The latterin Bellarmine's own hand andunquestioned authenticity;formeran unsigned copy, violatingInquisition's own rule thatrecordsuch an admonition hadbe signed by all partiesnotarized. Leaving aside technical rulesevidence, what can one conclude as toreal events? Theretwo schoolsthought. AccordingStillman Drake,order notteach was delivered unofficiallyimproperly; Bellarmine would not allowformal recordbe made,assured Galileowriting thatonly ordereffect was not"defend or hold". AccordingGiorgio di Santillana, however,unsigned minute was simplyfabrication byInquisition.

Despite his continued insistence that his work inarea was purely theoretical, despite his strict following ofchurch protocolpublicationworks (which required prior examination by church censorssubsequent permission),despite his close friendshipMaffeo Barberini who later became Pope Urban VIIIpresided throughoutordeal, Galileo was forcedrecant his views repeatedly,was put under life-long house arrest from 16331642.

The Inquisition had rejected earlier pleas by Galileopostpone or relocatetrial becausehis ill health. Atmeeting presided by Pope Urban VIII,Inquisition decidednotify Galileo that he either hadcomeRome or that he would be arrestedbrought therechains. Galileo arrivedRomehis trial beforeInquisition on February 13, 1633. After two weeksquarantine, Galileo was detained atcomfortable residence ofTuscan ambassador, asfavor toinfluential Grand Duke Ferdinand II de' Medici. In April 1633, he was formally interrogated byInquisition. He was not imprisoned indungeon cell, but detained inroom inoffices ofInquisition22 days.

On June 22, 1633,Roman Inquisition started its trial against Galileo, who was then 69 years oldpleadedmercy, pointinghis "regrettable statephysical unwellness". Threatening himtorture, imprisonment,death onstake,show trial forced Galileo"abjure, cursedetest" his work andpromisedenounce others who held his prior viewpoint. Galileo did everythingchurch requested himdo. Thatthreattorturedeath Galileo was facing wasreal one had been proven bychurch inearlier trial against Giordano Bruno, who was burned atstake1600holdingnaturalistic view ofUniverse.

The tale that Galileo, rising from his knees after recanting, said "Eppur si muove!" (Butdoes move!) cannot possibly be true;say any suchinoffices ofInquisition would have beenticketfollow Bruno tostake. Butwidespread belief thatwhole incidentan 18th-century inventionalso false. A Spanish painting, dated 1643 or possibly 1645, shows Galileo writingphrase onwall ofdungeon cell. Here we havesecond version ofstory, which also cannot be true, because Galileo was never imprisoned indungeon; butpainting shows that some story"Eppur si muove" was circulatingGalileo's time. Inmonths immediately after his condemnation, Galileo residedArchbishop Ascanio PiccolominiSiena,learned man andsympathetic host;fact that Piccolomini's brother wasmilitary attachéMadrid, wherepainting was made some years later, suggests thatArchbishop may have relatedstoryhis family,it later became garbledoral tradition.

Galileo was sentencedprison, but becausehis advanced age (and/or Church politics)sentence was commutedhouse arrest at his villasArcetriFlorence[1]. Because ofpainful hernia, he requested permissionconsult physiciansFlorence, which was denied by Rome, which warned that further such requests would leadimprisonment. Under arrest, he was forcedrecite penitentiary psalms regularly,his social contacts were at times highly restricted, but he was allowedcontinue his less controversial research.

Publication was another matter. His Dialogue had been put onIndex Librorum Prohibitorum,official black listbanned books, wherestayed until 1822 (Hellman, 1998). Thoughsentence announced against Galileo mentioned no other works, Galileo found out two years later that publicationanything he might ever write had been quietly banned. The ban was effectiveFrance, Poland,German states, but not inNetherlands.

He went totally blind1638 (his petition toInquisitionbe released was rejected, but he was allowedmovehis houseFlorence where he was closerhis physicians).

AccordingAndrew Dickson Whitemanyhis colleagues, Galileo's experiences demonstrateclassic case ofscholar forcedrecantscientific insight becauseoffended powerful, conservative forcessociety: forchurch attime,was notscientific method that should be usedfind truth -- especiallycertain areas -- butdoctrine as interpreteddefined by church scholars,this doctrine was defendedtorture, murder, deprivationfreedom,censorship.

More recently,viewpointsWhitehis colleagues have become less generally accepted byacademic community, partially because White wrote fromperspective that Christianity isdestructive force. This attitude can also be seen inworksBertolt Brecht, whose play about Galileoone ofchief sourcespopular ideas aboutscientist. Moreover, deeper examination ofprimary sourcesGalileohis trial shows that claimstorturedeprivation were likely exaggerated. Dava Sobel's Galileo's Daughter offersdifferent setinsights into Galileohis world,large part throughprivate correspondenceMaria Celeste,daughter oftitle,her father.

In 1992, 359 years afterGalileo trial, Pope John Paul II issued an apology, liftingedictInquisition against Galileo: "Galileo sensedhis scientific researchpresence ofCreator who, stirring indepthshis spirit, stimulated him, anticipatingassisting his intuitions." Afterreleasethis report,Pope said further that "... Galileo,sincere believer, showed himselfbe more perceptivethis regard [the relationscientificBiblical truths] thantheologians who opposed him."

Writings by Galileo

See also: Galilean transformation, Lorentz transformation equations

References

External links


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