pale blue dot -carl sagan-第6章

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ried　them　not　at　all。　That　some　of　their　deeply　held　beliefs　might　turn　out　to　be　mistakes　was　a　possibility　hardly　considered。　Doctrinal　humility　was　to　be　practiced　by　others。　Their　own　teachings　were　inerrant　and　Infallible。　In　truth；　they　had　better　reason　to　be　humble　than　they　knew。



BEGINNING　WITH　COPERNICUS　in　the　middle　sixteenth　century；　the　issue　was　formally　joined。　The　picture　of　the　Sun　rather　than　the　Earth　at　the　center　of　the　Universe　was　understood　to　be　dangerous。　Obligingly；　many　scholars　were　quick　to　assure　the　religious　hierarchy　that　this　newfangled　hypothesis　represented　no　serious　challenge　to　conventional　wisdom。　In　a　kind　of　split…brain　promise；　the　Sun…centered　system　was　treated　as　a　mere　putational　convenience；　not　an　astronomical　reality　that　is；　the　Earth　was　really　at　the　center　of　the　Universe；　as　everybody　knew；　but　if　you　wished　to　predict　where　Jupiter　would　be　on　the　second　Tuesday　of　November　the　year　after　next；　you　were　permitted　to　pretend　that　the　Sun　was　at　the　center。　Then　you　could　calculate　away　and　not　affront　the　Authorities。*

*　Copernicus'　famous　book　was　first　published　with　an　introduction　by　the　theologian　Andrew　Osiander；　inserted　without　the　knowledge　of　the　dying　astronomer。　Osiander's　well…meaning　attempt　to　reconcile　religion　and　Copernican　astronomy　ended　with　these　words：　〃＇L＇et　no　one　expect　anything　in　the　way　of　certainty　of　astronomy；　since　astronomy　can　offer　us　nothing　certain；　lest；　if　anyone　take　as　true　that　which　has　been　constructed　for　。mother　use；　he　go　away　from　this　discipline　a　bigger　fool　than　w　hen　he　cane　to　it。〃　Certainty　could　be　found　only　in　religion。

〃This　has　no　danger　in　it；〃　wrote　Robert　Cardinal　Bellarmine；　the　foremost　Vatican　theologian　in　the　early　seventeenth　century；　and　suffices　for　the　mathematicians。　But；　to　affirm　that　the　Sun　is　really　fixed　in　the　center　of　the　heavens　and　that　the　Earth　revolves　very　swiftly　around　the　Sun　is　a　dangerous　thing；　not　only　irritating　the　theologians　and　philosophers；　but　injuring　our　holy　faith　and　making　the　sacred　scripture　false。〃

〃Freedom　of　belief　is　pernicious；〃　Bellarmine　wrote　on　another　occasion。　〃It　is　nothing　but　the　freedom　to　be　wrong。〃

Besides；　if　the　Earth　was　going　around　the　Sun；　nearby　stars　should　seem　to　move　against　the　background　of　more　distant　stars　as；　every　six　months；　we　shift　our　perspective　from　one　side　of　the　Earth's　orbit　to　the　other。　No　such　〃annual　parallax〃　had　been　found。　The　Copernicans　argued　that　this　was　because　the　stars　were　extremely　far　away—maybe　a　million　times　more　distant　than　the　Earth　is　from　the　Sun。　Perhaps　better　telescopes；　in　future　times；　would　find　an　annual　parallax。　The　geocentrists　considered　this　a　desperate　attempt　to　save　a　flawed　hypothesis；　and　ludicrous　on　the　face　of　it。

When　Galileo　turned　the　first　astronomical　telescope　to　the　sky；　the　tide　began　to　turn。　He　discovered　that　Jupiter　had　a　little　retinue　of　moons　circling　it；　the　inner　ones　orbiting　faster　than　the　outer　ones；　just　as　Copernicus　had　deduced　for　the　motion　of　the　planets　about　the　Sun。　He　found　that　Mercury　and　Venus　went　through　phases　like　the　Moon　（showing　they　orbited　the　Sun）。　Moreover；　the　cratered　Moon　and　the　spotted　Sun　challenged　the　perfection　of　the　heavens。　This　may　in　part　constitute　the　sort　of　trouble　Tertullian　was　worried　about　thirteen　hundred　years　earlier；　when　he　pleaded；　〃If　you　have　any　sense　or　modesty；　have　done　with　prying　into　the　regions　of　the　sky；　into　the　destiny　and　secrets　of　the　universe。〃

In　contrast；　Galileo　taught　that　we　can　interrogate　Nature　by　observation　and　experiment。　Then；　〃facts　which　at　first　sight　seem　improbable　will；　even　on　scant　explanation；　drop　the　cloak　which　had　hidden　them　and　stand　forth　in　naked　and　simple　beauty。〃　Are　not　these　facts；　available　even　for　skeptics　to

confirm；　a　surer　insight　into　God's　Universe　than　all　the　speculations　of　the　theologians？　But　what　if　these　facts　contradict　the　beliefs　of　those　who　hold　their　religion　incapable　of　making　mistakes？　The　princes　of　the　Church　threatened　the　aged　astronomer　with　torture　if　he　persisted　in　teaching　the　abominable　doctrine　that　the　Earth　moved。　He　was　sentenced　to　a　kind　of　house　arrest　for　the　remainder　of　his　life。

A　generation　or　two　later；　by　the　time　Isaac　Newton　demonstrated　that　simple　and　elegant　physics　could　quantitatively　explain—and　predict—all　the　observed　lunar　and　planetary　motions　（provided　you　assumed　the　Sun　at　the　center　of　the　Solar　System）；　the　geocentrist　conceit　eroded　further。

In　1725；　in　an　attempt　to　discover　stellar　parallax；　the　painstaking　English　amateur　astronomer　James　Bradley　stumbled　on　the　aberration　of　light。　The　term　〃aberration；〃　I　suppose；　conveys　something　of　the　unexpectedness　of　the　discovery。　When　observed　over　the　course　of　a　year；　stars　were　found　to　trace　little　ellipses　against　the　sky。　But　all　the　stars　were　found　to　do　so。　This　could　not　be　stellar　parallax；　where　we　would　expect　a　big　parallax　for　nearby　stars　and　an　indetectible　one　for　faraway　stars。　Instead；　aberration　is　similar　to　how　raindrop　falling　directly　down　on　a　speeding　auto　seem　to　the　passenger；　to　be　falling　at　a　slant；　the　faster　the　car　goes；　the　steeper　the　slant。　If　the　Earth　were　stationary　at　the　center　of　the　Universe。　and　not　speeding　in　its　orbit　around　the　Sun；　Bradley　would　nor　have　found　the　aberration　of　light。　It　was　a　pelling　demonstration　that　the　Earth　revolved　about　the　Sun。　It　convinced　most　astronomers　and　some　others　but　not；　Bradley　thought；　the　〃Anti…Copernicans。〃

But　not　until　1837　did　direct　observations　of　the　stars　prove　in　the　clearest　way　that　the　Earth　is　indeed　circling　the　Sun。　The　long…debated　annual　parallax　was　at　last　discovered—not　by　better　arguments；　but　by　better　instruments。　Because　explaining　what　it　means　is　much　more　straightforward　than　explaining　the　aberration　of　light；　its　discovery　was　very　important。　It　pounded　the　final　nail　into　the　coffin　of　geocentrism。　You　need　only　look　at　your　finger　with　your　left　eye　and　then　with　your　right　and　see　it　seem　to　move。　Everyone　can　understand　parallax。

By　the　nineteenth　century；　all　scientific　geocentrists　had　been　converted　or　rendered　extinct。　Once　most　scientists　had　been　convinced；　informed　public　opinion　had　swiftly　changed；　in　some　countries　in　a　mere　three　or　four　generations。　Of　course；　in　the　time　of　Galileo　and　Newton　and　even　much　later；　there　were　still　some　who　objected；　who　tried　to　prevent　the　new　Sun…centered　Universe　from　being　accepted；　or　even　known。　And　there　were　many　who　at　least　harbored　secret　reservations。

By　the　late　twentieth　century；　just　in　case　there　were　any　holdouts；　we　have　been　able　to　settle　the　matter　directly。　We've　been　able　to　test　whether　we　live　in　an　Earth…centered　system　with　planets　affixed　to　transparent　crystal　spheres；　or　in　a　Sun…centered　system　with　planets　controlled　at　a　distance　by　the　gravity　of　the　Sun。　We　have；　for　example；　probed　the　planets　with　radar。　When　we　bounce　a　signal　off　a　moon　of　Saturn；　we　receive　no　radio　echo　from　a　nearer　crystal　sphere　attached　to　Jupiter。　Our　spacecraft　arrive　at　their　appointed　destinations　with　astonishing　precision；　exactly　as　predicted　by　Newtonian　gravitation。　When　our　ships　fly　to　Mars；　say；　their　instruments　do　not　hear　a　tinkling　sound　or　detect　shards　of　broken　crystal　as　they　crash　through　the　〃spheres〃　that—according　to　the　authoritative　opinions　that　prevailed　for　millennia—propel　Venus　or　the　Sun　ill　their　dutiful　motions　about　the　central　Earth。

When　Voyager　1　scanned　the　Solar　System　from　beyond　the　outermost　planet；　it　saw；　just　as　Copernicus　and　Galileo　had　said　we　would；　the　Sun　in　the　middle　and　the　planets　in　concentric　orbits　about　it。　Far　from　being　the　center　of　the　Universe；　the　Earth　is　just　one　of　the　orbiting　dots。　No　longer　confined　to　a　single　world；　we　are　now　able　to　reach　out　to　others　and　determine　decisively　what　kind　of　planetary　system　we　inhabit。



EVERY　OTHER　PROPOSAL；　and　their　number　is　legion；　to　displace　us　from　cosmic　center　stage　has　also　been　resisted；　in　part　for　similar　reasons。　We　seem　to　crave　privilege；　merited　not　by　our　work；　but　by　our　birth；　by　the　mere