BiographiesofCharacters
D'Alembert(2photos)
Pierre-SimonLaplace,Frenchmathematicianandastronomer,AcademicianoftheFrenchAcademyofSciences.Heisthemainfounderofcelestialmechanicsandoneofthefoundersofastronomicalchemistry.Heisalsothefounderofanalyticalprobabilitytheory,sohecanbesaidtobeapioneerofappliedmathematics.BornonMarch23,1749inBeaumont-en-Hanoge,Calvados,northwesternFrance,hewasaprofessorofmathematicsattheParisMilitaryAcademy.In1795,heservedasaprofessorattheParisPolytechnicSchoolandlaterattheNormalSchoolofHigherEducation.In1799healsoservedasdirectoroftheFrenchLongitudeBureau,andservedasMinisteroftheInteriorintheNapoleonicgovernmentfor6weeks.HewaselectedasamemberoftheFrenchAcademyin1816,andin1817heservedasthedeanoftheAcademy.DiedinParisonMarch5,1827.Intheprocessofstudyingtheproblemofcelestialbodies,Laplacecreatedanddevelopedmanymathematicalmethods.TheLaplacetransform,Laplacetheorem,andLaplaceequationnamedafterhimareusedinvariousfieldsofscienceandtechnology.Thefieldhasawiderangeofapplications.LaplacewasborninBeaumont,Normandy,France.Hisfatherwasafarmer.Heshowedoutstandingmathematicstalentssincehisyouth.Attheageof18,helefthomeandwenttoParisanddecidedtoworkinmathematics.SohebroughtaletterofrecommendationtoD'Alembert,afamousFrenchscholaratthetime,butwasrefusedbythelatter.LaplacesentapaperonmechanicstoD'Alembert.ThepaperwassoexcellentthatD'Alembertwassuddenlysohappytobehisgodfather,andLaplacewasrecommendedtoteachatthemilitaryschool.
Afterthat,heworkedwithLavoisierforaperiodoftime,andtheymeasuredthespecificheatofmanysubstances.In1780,thetwoofthemprovedthattheheatrequiredtodecomposeacompoundintoitsconstituentelementsisequaltotheheatreleasedbytheseelementswhenformingthecompound.Thiscanbeseenasthebeginningofthermochemistry,anditisalsoanothermilestoneintheadvancementofthelawofconservationofenergyafterBraque’sresearchonlatentheat,whichwasfinallybornafter60years.
Personalcontribution
Laplacefocusedhisattentiononthestudyofcelestialmechanics.HeappliedNewton'slawofuniversalgravitationtotheentiresolarsystem.In1773,hesolvedafamousproblematthetime:explainwhytheorbitofJupiterisconstantlyshrinking,whiletheorbitofSaturnisconstantlyexpanding.Laplaceusedmathematicalmethodstoprovetheinvarianceoftheaverageplanetarymotion,thatis,theorbitalsizeoftheplanetonlychangesperiodically,andprovedtobethethirdpowerofeccentricityandinclination.ThisisthefamousLaplacetheorem.Afterthat,hebegantostudythestabilityofthesolarsystem.Inthesameyear,hebecameanassociatememberoftheFrenchAcademyofSciences.
From1784to1785,hefoundthatthegravitationalcomponentofacelestialbodytoanyparticleoutsideitcanbeexpressedbyapotentialfunction,whichsatisfiesapartialdifferentialequation,thefamousLaplaceequation.In1785hewaselectedamemberoftheAcademyofSciences.
In1786,itwasprovedthattheeccentricityandinclinationofplanetaryorbitsarealwayskeptsmallandconstant,andcanbeadjustedautomatically.Thatis,theperturbationeffectisconservedandperiodic,andwillnotaccumulateordissolve.LaplacenoticedthattheaveragemotionsZ1,Z2,andZ3ofJupiter'sthreemainmoonsobeythefollowingrelationship:Z1-3×Z2+2×Z3=0.Similarly,theaveragemotionsY1,Y2,Y3,andY4ofthefourmoonsofSaturnalsohaveasimilarrelationship:5×Y1-10×Y2+Y3+4×Y4=0.Latergenerationsclaimedthattherewascommensurabilitybetweenthesesatellites,whichevolvedtheconceptofawindowoftime.
Itwasdiscoveredin1787thattheaccelerationofthemoonisrelatedtotheeccentricityoftheearth'sorbit,whichtheoreticallysolvedthelastanomalyobservedinthedynamicsofthesolarsystem.
In1796,hisbook"OntheSystemoftheUniverse"cameout.Thebookputforwardthenebulahypothesisabouttheoriginofplanetsthathadasignificantinfluenceonthelater.Inthisbook,independentofKant,heproposedthefirstscientifictheoryoftheoriginofthesolarsystem-NebulaTheory.Kant’snebulatheorywasproposedfromaphilosophicalpointofview,whileLaplaceenrichedthenebulatheoryfromtheperspectiveofmathematicsandmechanics.Therefore,peopleoftenrefertothenebulatheoryofthetwoofthemas"Kant-LaplaceNebulaTheory"..
Hehasbeenengagedinthestudyofthetheoryofmotionoflargeplanetsandthetheoryofmotionofthemoonforalongtime,especiallyhepaidspecialattentiontothestudyofsolarsystemcelestialbodyperturbation,thegeneralstabilityofthesolarsystemandthedynamicsofsolarsystemstability.Alargenumberofimportantresultshavebeenobtainedonthebasisofsummarizingpreviousstudies.Theseresultsareconcentratedinthe5volumesand16volumesofthemasterpiece"CelestialMechanics"publishedfrom1799to1825.Thetermcelestialmechanicswasfirstproposedinthisbook,whichisarepresentativeworkofclassicalcelestialmechanics.Therefore,heisknownastheFrenchNewtonandthefatherofcelestialmechanics.In1814,Laplaceputforwardascientifichypothesis,assumingthatifanintelligentorganismcandeterminethecurrentstateofmovementfromthelargestcelestialbodytothelightestatom,itcancalculatethepastandfuturestatesoftheentireuniverseaccordingtothelawsofmechanics.LatergenerationscalledtheintelligentcreatureheassumedastheLaplacedemon.
Healsomadegreatcontributionstomathematics,especiallyprobabilitytheory.
Hehaspublishedmorethan270papersonastronomy,mathematicsandphysics,withatotalofmorethan4006pages.Amongthemostrepresentativemonographsare"CelestialMechanics"(TraitédeMécaniqueCéleste,15volumes,16volumes,1799-1825),"TheoryoftheUniverseSystem"(Expositiondusystèmedumonde,1796,Chinesetranslation,1978edition)and"ProbabilityAnalysis"Theory"(TheorieAnalytiquedesProbabilites,1812).
WithNapoleon
LaplaceusedtobeNapoleon’steacher,sohehadanindissolublebondwithNapoleon.Laplaceisamasterinmathematics,alittlemaninpolitics,heisalwaysloyaltothedominantside,andislookeddownuponbyothers.Napoleononceridiculedhimforbringingtheinfinitesimalspirittothecabinet.ThepoliticalchangessweepingFrance,includingtheriseandfallofNapoleon,didnotsignificantlyinterrupthiswork.Althoughhewasapoliticalman,hisprestigeandhisabilitytoapplymathematicstomilitaryproblemsprotectedhim,andhealsoowedhimanunadmirablepoliticalattitude.Ability.