a history of science-2-第8章

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stion　of　the　earth's　position　in　the　universe。　Therefore　the　voyage　of　Magellan　served　to　fortify；　rather　than　to　dispute；　the　Ptolemaic　theory。　According　to　that　theory；　as　we　have　seen；　the　earth　was　supposed　to　lie　immovable　at　the　centre　of　the　universe；　the　various　heavenly　bodies；　including　the　sun；　revolving　about　it　in　eccentric　circles。　We　have　seen　that　several　of　the　ancient　Greeks；　notably　Aristarchus；　disputed　this　conception；　declaring　for　the　central　position　of　the　sun　in　the　universe；　and　the　motion　of　the　earth　and　other　planets　about　that　body。　But　this　revolutionary　theory　seemed　so　opposed　to　the　ordinary　observation　that；　having　been　discountenanced　by　Hipparchus　and　Ptolemy；　it　did　not　find　a　single　important　champion　for　more　than　a　thousand　years　after　the　time　of　the　last　great　Alexandrian　astronomer。　The　first　man；　seemingly；　to　hark　back　to　the　Aristarchian　conception　in　the　new　scientific　era　that　was　now　dawning　was　the　noted　cardinal；　Nikolaus　of　Cusa；　who　lived　in　the　first　half　of　the　fifteenth　century；　and　was　distinguished　as　a　philosophical　writer　and　mathematician。　His　De　Docta　Ignorantia　expressly　propounds　the　doctrine　of　the　earth's　motion。　No　one；　however；　paid　the　slightest　attention　to　his　suggestion；　which；　therefore；　merely　serves　to　furnish　us　with　another　interesting　illustration　of　the　futility　of　propounding　even　a　correct　hypothesis　before　the　time　is　ripe　to　receive　itparticularly　if　the　hypothesis　is　not　fully　fortified　by　reasoning　based　on　experiment　or　observation。　The　man　who　was　destined　to　put　forward　the　theory　of　the　earth's　motion　in　a　way　to　command　attention　was　born　in　1473；　at　the　village　of　Thorn；　in　eastern　Prussia。　His　name　was　Nicholas　Copernicus。　There　is　no　more　famous　name　in　the　entire　annals　of　science　than　this；　yet　posterity　has　never　been　able　fully　to　establish　the　lineage　of　the　famous　expositor　of　the　true　doctrine　of　the　solar　system。　The　city　of　Thorn　lies　in　a　province　of　that　border　territory　which　was　then　under　control　of　Poland；　but　which　subsequently　became　a　part　of　Prussia。　It　is　claimed　that　the　aspects　of　the　city　were　essentially　German；　and　it　is　admitted　that　the　mother　of　Copernicus　belonged　to　that　race。　The　nationality　of　the　father　is　more　in　doubt；　but　it　is　urged　that　Copernicus　used　German　as　his　mother…tongue。　His　great　work　was；　of　course；　written　in　Latin；　according　to　the　custom　of　the　time；　but　it　is　said　that；　when　not　employing　that　language；　he　always　wrote　in　German。　The　disputed　nationality　of　Copernicus　strongly　suggests　that　he　came　of　a　mixed　racial　lineage；　and　we　are　reminded　again　of　the　influences　of　those　ethnical　minglings　to　which　we　have　previously　more　than　once　referred。　The　acknowledged　centres　of　civilization　towards　the　close　of　the　fifteenth　century　were　Italy　and　Spain。　Therefore；　the　birthplace　of　Copernicus　lay　almost　at　the　confines　of　civilization；　reminding　us　of　that　earlier　period　when　Greece　was　the　centre　of　culture；　but　when　the　great　Greek　thinkers　were　born　in　Asia　Minor　and　in　Italy。　As　a　young　man；　Copernicus　made　his　way　to　Vienna　to　study　medicine；　and　subsequently　he　journeyed　into　Italy　and　remained　there　many　years；　About　the　year　1500　he　held　the　chair　of　mathematics　in　a　college　at　Rome。　Subsequently　he　returned　to　his　native　land　and　passed　his　remaining　years　there；　dying　at　Domkerr；　in　Frauenburg；　East　Prussia；　in　the　year　1543。　It　would　appear　that　Copernicus　conceived　the　idea　of　the　heliocentric　system　of　the　universe　while　he　was　a　comparatively　young　man；　since　in　the　introduction　to　his　great　work；　which　he　addressed　to　Pope　Paul　III。；　he　states　that　he　has　pondered　his　system　not　merely　nine　years；　in　accordance　with　the　maxim　of　Horace；　but　well　into　the　fourth　period　of　nine　years。　Throughout　a　considerable　portion　of　this　period　the　great　work　of　Copernicus　was　in　manuscript；　but　it　was　not　published　until　the　year　of　his　death。　The　reasons　for　the　delay　are　not　very　fully　established。　Copernicus　undoubtedly　taught　his　system　throughout　the　later　decades　of　his　life。　He　himself　tells　us　that　he　had　even　questioned　whether　it　were　not　better　for　him　to　confine　himself　to　such　verbal　teaching；　following　thus　the　example　of　Pythagoras。　Just　as　his　life　was　drawing　to　a　close；　he　decided　to　pursue　the　opposite　course；　and　the　first　copy　of　his　work　is　said　to　have　been　placed　in　his　hands　as　he　lay　on　his　deathbed。　The　violent　opposition　which　the　new　system　met　from　ecclesiastical　sources　led　subsequent　commentators　to　suppose　that　Copernicus　had　delayed　publication　of　his　work　through　fear　of　the　church　authorities。　There　seems；　however；　to　be　no　direct　evidence　for　this　opinion。　It　has　been　thought　significant　that　Copernicus　addressed　his　work　to　the　pope。　It　is；　of　course；　quite　conceivable　that　the　aged　astronomer　might　wish　by　this　means　to　demonstrate　that　he　wrote　in　no　spirit　of　hostility　to　the　church。　His　address　to　the　pope　might　have　been　considered　as　a　desirable　shield　precisely　because　the　author　recognized　that　his　work　must　needs　meet　with　ecclesiastical　criticism。　Be　that　as　it　may；　Copernicus　was　removed　by　death　from　the　danger　of　attack；　and　it　remained　for　his　disciples　of　a　later　generation　to　run　the　gauntlet　of　criticism　and　suffer　the　charges　of　heresy。　The　work　of　Copernicus；　published　thus　in　the　year　1543　at　Nuremberg；　bears　the　title　De　Orbium　Coelestium　Revolutionibus。　It　is　not　necessary　to　go　into　details　as　to　the　cosmological　system　which　Copernicus　advocated；　since　it　is　familiar　to　every　one。　In　a　word；　he　supposed　the　sun　to　be　the　centre　of　all　the　planetary　motions；　the　earth　taking　its　place　among　the　other　planets；　the　list　of　which；　as　known　at　that　time；　comprised　Mercury；　Venus；　the　Earth；　Mars；　Jupiter；　and　Saturn。　The　fixed　stars　were　alleged　to　be　stationary；　and　it　was　necessary　to　suppose　that　they　are　almost　infinitely　distant；　inasmuch　as　they　showed　to　the　observers　of　that　time　no　parallax；　that　is　to　say；　they　preserved　the　same　apparent　position　when　viewed　from　the　opposite　points　of　the　earth's　orbit。　But　let　us　allow　Copernicus　to　speak　for　himself　regarding　his　system；　His　exposition　is　full　of　interest。　We　quote　first　the　introduction　just　referred　to；　in　which　appeal　is　made　directly　to　the　pope。　〃I　can　well　believe；　most　holy　father；　that　certain　people；　when　they　hear　of　my　attributing　motion　to　the　earth　in　these　books　of　mine；　will　at　once　declare　that　such　an　opinion　ought　to　be　rejected。　Now；　my　own　theories　do　not　please　me　so　much　as　not　to　consider　what　others　may　judge　of　them。　Accordingly；　when　I　began　to　reflect　upon　what　those　persons　who　accept　the　stability　of　the　earth；　as　confirmed　by　the　opinion　of　many　centuries；　would　say　when　I　claimed　that　the　earth　moves；　I　hesitated　for　a　long　time　as　to　whether　I　should　publish　that　which　I　have　written　to　demonstrate　its　motion；　or　whether　it　would　not　be　better　to　follow　the　example　of　the　Pythagoreans；　who　used　to　hand　down　the　secrets　of　philosophy　to　their　relatives　and　friends　only　in　oral　form。　As　I　well　considered　all　this；　I　was　almost　impelled　to　put　the　finished　work　wholly　aside；　through　the　scorn　I　had　reason　to　anticipate　on　account　of　the　newness　and　apparent　contrariness　to　reason　of　my　theory。　〃My　friends；　however；　dissuaded　me　from　such　a　course　and　admonished　me　that　I　ought　to　publish　my　book；　which　had　lain　concealed　in　my　possession　not　only　nine　years；　but　already　into　four　times　the　ninth　year。　Not　a　few　other　distinguished　and　very　learned　men　asked　me　to　do　the　same　thing；　and　told　me　that　I　ought　not；　on　account　of　my　anxiety；　to　delay　any　longer　in　consecrating　my　work　to　the　general　service　of　mathematicians。　〃But　your　holiness　will　perhaps　not　so　much　wonder　that　I　have　dared　to　bring　the　results　of　my　night　labors　to　the　light　of　day；　after　having　taken　so　much　care　in　elaborating　them；　but　is　waiting　instead　to　hear　how　it　entered　my　mind　to　imagine　that　the　earth　moved；　contrary　to　the　accepted　opinion　of　mathematiciansnay；　almost　contrary　to　ordinary　human　understanding。　Therefore　I　will　not　conceal　from　your　holiness　that　what　moved　me　to　consider　another　way　of　reckoning　the　motions　of　the　heavenly　bodies　was　nothing　else　than　the　fact　that　the　mathematicians　do　not　agree　with　one　another　in　their　investigations。　In　the　first　place；　they　are　so　uncertain　about　the　motions　of　the　sun　and　moon　that　they　cannot　find　out　the　length　of　a　full　year。　In　the　second　place；　they　apply　neither　the　same　laws　of　cause　and　effect；　in　determining　the　motions　of　the　sun　and　moon　and　of　the　five　planets；　nor　the　same　proofs。　Some　employ　only　concentric　circles；　others　use　eccentric　and　epicyclic　ones；　with　which；　however；　they　do　not　fully　attain　the　desired　end。　They　could　not　even　discover　nor　compute　the　main　thingnamely；　the　form　of　the　universe　and　the　symmetry　of　its　parts。　It　was　with　them　as　if　some　should；　from　different　places；　take　hands；　feet；　head；　and　other　parts　of　the　body；　which；　although　very　beautiful；　were　not　drawn　in　their　proper　relations；　and；　without　making　them　in　any　way　correspond；　should　construct　a　monster　instead　of　a　human　being。　〃Accordingly；　when　I　had　long　reflected　on　this　uncertainty　of　mathematical　tradition；　I　took　the　trouble　to　read　again　the　books　of　all　the　philosophers　I　could　get　hold　of；　to　see　if　some　one　of　them　had　not　once　believed　that　there　were　other　motions　of　the　heavenly　bodies。　First　I　found　in　Cicero　that　Niceties　had　believed　in　the　motion　of　the　earth。　Afterwards　I　found　in　Plutarch；　likewise；　that　some　others　had　held　the　same　opinion。　This　induced　me　also　to　begin　to　consider　the　movability　of　the　earth；　and；　although　the　theory　appeared　contrary　to　reason；　I　did　so　because　I　knew　that　others　before　me　had　been　allowed　to　assume　rotary　movements　at　will；　in　order　to　explain　the　phenomena　of　these　celestial　bodies。　I　was　of　the　opinion　that　I；　too；　might　be　permitted　to　see　whether；　by　presupposing　motion　in　the　earth；　more　reliable　conclusions　than　hitherto　reached　could　not　be　discovered　for　the　rotary　motions　of　the　spheres。　And　thus；　acting　on　the　hypothesis　of　the　motion　which；　in　the　following　book；　I　ascribe　to　the　earth；　and　by　long　and　continued　observations；　I　have　finally　discovered　that　if　the　motion　of　the　other　planets　be　carried　over　to　the　relation　of　the　earth　and　this　is　made　the　basis　for　the　rotation　of　every　star；　not　only　will　the　phenomena　of　the　planets　be　explained　thereby；　but　also　the　laws　and　the　size　of　the　stars；　all　their　spheres　and　the　heavens　themselves　will　appear　so　harmoniously　connected　that　nothing　could　be　changed　in　any　part　of　them　without　confusion　in　the　remaining　parts　and　in　the　whole　universe。　I　do　not　doubt　that　clever　and　learned　men　will　agree　with　me　if　they　are　willing　fully　to　comprehend　and　to　consider　the　proofs　which　I　advance　in　the　book　before　us。　In　order；　however；　that　both　the　learned　and　the　unlearned　may　see　that　I　fear　no　man's　judgment；　I　wanted　to　dedicate　these；　my　night　labors；　to　your　holiness；　rather　than　to　any　one　else；　because　you；　even　in　this　remote　corner　of　the　earth　where　I　live；　are　held　to　be　the　greatest　in　dignity　of　station　and　in　love　for　all　sciences　and　for　mathematics；　so　that　you；　through　your　position　a