pale blue dot -carl sagan-第9章

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　the　position　of　Origen；　of　St。　Ambrose　（the　mentor　of　St。　Augustine）；　and　even；　in　a　more　qualified　form；　of　St。　Thomas　Aquinas。　The　Stoic　philosophical　position　on　the　Sun's　nature　was　stated　by　Cicero；　in　the　first　century　B。C。：　〃Since　the　Sun　resembles　those　fires　which　are　contained　in　the　bodies　of　living　creatures；　the　Sun　must　also　be　alive。〃

Animist　attitudes　in　general　seem　to　have　been　spreading　recently。　In　a　1954　American　survey；　75　percent　of　people　polled　were　willing　to　state　that　the　Sun　is　not　alive；　in　1989；　only　30　percent　would　support　so　rash　a　proposition。　On　whether　an　automobile　tire　can　feel　anything；　90　percent　of　respondents　denied　it　emotions　in　1954；　but　only　73　percent　in　1989。

We　can　recognize　here　a　shorting—in　some　circumstances　serious—in　our　ability　to　understand　the　world。　Characteristically；　willy…nilly；　we　seem　pelled　to　project　our　own　nature　onto　Nature。　Although　this　may　result　in　a　consistently　distorted　view　of　the　world；　it　does　have　one　great　virtue—projection　is　the　essential　precondition　for　passion。

Okay；　maybe　we're　not　much；　maybe　we're　humiliatingly　related　t0　apes；　but　at　least　we're　the　best　there　is。　God　and　angels　aside；　we're　the　only　intelligent　beings　in　the　Universe。　One　correspondent　writes　to　me；　〃I　am　as　sure　of　this　as　anything　in　my　experience。　There　is　no　conscious　life　anywhere　else　in　the　Universe。　Mankind　thus　returns　to　its　rightful　position　as　center　of　the　universe。〃　However；　partly　through　the　influence　of　science　acid　science　fiction；　most　people　today；　in　the　United　States　at　least；　reject　this　proposition—for　reasons　essentially　stated　by　the　ancient　Greek　philosopher　Chrysippus：　〃For　any　human　being　in　existence　to　think　that　there　is　nothing　in　the　whole　world　superior　to　himself　would　be　an　insane　piece　of　arrogance。〃

But　the　simple　fact　is　that　we　have　not　yet　found　extraterrestrial　life。　We　are　in　the　earliest　stages　of　looking。　The　question　is　wide　open。　If　I　had　to　guess—especially　considering　our　long　sequence　of　failed　I　would　guess　that　the　Universe　is　filled　with　beings　far　more　intelligent；　tar　more　advanced　than　we　are。　But　of　course　I　might　be　wrong。　Such　a　conclusion　is　at　best　based　on　a　plausibility　argument；　derived　from　the　numbers　of　planets；　the　ubiquity　of　organic　matter；　the　immense　timescales　available　for　evolution；　and　so　on。　It　is　not　a　scientific　demonstration。　The　question　is　among　the　most　fascinating　in　all　of　science。　As　described　in　this　book；　we　are　just　developing　the　tools　to　treat　it　seriously。

What　about　the　related　matter　of　whether　we　are　capable　of　creating　intelligences　smarter　than　ourselves？　puters　routinely　do　mathematics　that　no　unaided　human　can　manage；　outperform　world　champions　in　checkers　and　grand　masters　in　chess；　speak　and　understand　English　and　other　languages；　write　presentable　short　stories　and　musical　positions；　learn　from　their　mistakes；　and　petently　pilot　ships；　airplanes；　and　spacecraft。　Their　abilities　steadily　improve。　They're　getting　smaller；　faster；　and　cheaper。　Each　year；　the　tide　of　scientific　advance　laps　a　little　further　ashore　on　the　island　of　human　intellectual　uniqueness　with　its　embattled　castaways。　If；　at　so　early　a　stage　in　our　technological　evolution；　we　have　been　able　to　go　so　far　in　creating　intelligence　out　of　silicon　and　metal；　what　will　be　possible　in　the　following　decades　and　centuries？　What　happens　when　smart　machines　are　able　to　manufacture　smarter　machines？



PERHAPS　THE　CLEAREST　INDICATION　that　the　search　for　an　unmerited　privileged　position　for　humans　will　never　be　wholly　abandoned　is　what　in　physics　and　astronomy　is　called　the　Anthropic　Principle。　It　would　be　better　named　the　Anthropocentric　Principle。　It　es　in　various　forms。　The　〃Weak〃　Anthropic　Principle　merely　notes　that　if　the　laws　of　Nature　and　the　physical　constants—such　as　the　speed　of　light；　the　electrical　charge　of　the　electron；　the　Newtonian　gravitational　constant；　or　Planck's　quantum　mechanical　constant　had　been　different；　the　course　of　events　leading　to　the　origin　of　humans　would　never　have　transpired。　Under　other　laws　and　constants；　atoms　would　not　hold　together；　stars　would　evolve　too　quickly　to　leave　sufficient　time　for　life　to　evolve　on　nearby　planets；　the　chemical　elements　of　which　life　is　made　would　never　have　been　generated；　and　so　on。　Different　laws；　no　humans。

There　is　no　controversy　about　the　Weak　Anthropic　Principle：　Change　the　laws　and　constants　of　Nature；　if　you　could；　and　a　very　different　universe　may　emerge—in　many　cases；　a　universe　inpatible　with　life。*　The　mere　fact　that　we　exist　implies　（but　does　not　impose）　constraints　on　the　laws　of　Nature。　In　contrast；　the　various　〃Strong〃　Anthropic　Principles　go　much　farther；　some　of　their　advocates　e　close　to　deducing　that　the　laws　of　Nature　and　the　values　of　the　physical　constants　were　established　（don't　ask　how　or　by　Whom）　so　that　humans　would　eventually　e　to　be。　Almost　all　of　the　other　possible　universes；　they　say；　are　inhospitable。　In　this　way；　the　ancient　conceit　that　the　Universe　was　made　for　us　is　resuscitated。

*　Our　universe　is　almost　inpatible　with　life—or　at　least　what　we　understand　as　necessary　for　life：　Even　if　every　star　in　a　hundred　billion　galaxies　had　an　Earthlike　planet；　without　heroic　technological　measures　life　could　prosper　in　only　about　10…37　the　volume　of　the　Universe。　For　clarity；　let's　write　it　out：　only　0。000　000　000　000　000　000　000　000　000　000　000　000　1　of　our　universe　is　hospitable　to　life。　Thirty…six　zeroes　before　the　one。　The　rest　is　cold；　radiation…riddled　black　vacuum。

To　me　it　echoes　Dr。　Pangloss　in　Voltaire's　Candide；　convinced　that　this　world；　with　all　its　imperfections；　is　the　best　possible。　It　sounds　like　playing　my　first　hand　of　bridge；　winning；　knowing　that　there　are　54　billion　billion　billion　（5。4　X　1028）　possible　other　hands　that　I　was　equally　likely　to　have　been　dealt　。　。　。　and　then　foolishly　concluding　that　a　god　of　bridge　exists　and　favors　me；　a　god　who　arranged　the　cards　and　the　shuffle　with　my　victory　foreordained　from　The　Beginning。　We　do　not　know　how　many　other　winning　hands　there　are　in　the　cosmic　deck；　how　many　other　kinds　of　universes；　laws　of　Nature；　and　physical　constants：　that　could　also　lead　to　life　and　Intelligence　and　perhaps　even　delusions　of　self…importance。　Since　we　know　next　to　nothing　about　how　the　Universe　was　made—or　even　if　it　was　made—it's　difficult　to　pursue　these　notions　productively。

Voltaire　asked　〃Why　is　there　anything？〃　Einstein's　formulation　was　to　ask　whether　God　had　any　choice　in　creating　the　Universe。　But　if　the　Universe　is　infinitely　old—if　the　Big　Bang　some　15　billion　years　ago　is　only　the　most　recent　cusp　in　an　infinite　series　of　cosmic　contractions　and　expansions—then　it　was　never　created　and　the　question　of　why　it　is　as　it　is　is　rendered　meaningless。

If；　on　the　other　hand；　the　Universe　has　a　finite　age；　why　is　it　the　way　it　is？　Why　wasn't　it　given　a　very　different　character？　Which　laws　of　Nature　go　with　which　others？　Are　there　meta…laws　specifying　the　connections？　Can　we　possibly　discover　them？　Of　all　conceivable　laws　of　gravity；　say；　which　ones　can　exist　simultaneously　with　which　conceivable　laws　of　quantum　physics　that　determine　the　very　existence　of　macroscopic　matter？　Are　all　laws　we　can　think　of　possible；　or　is　there　only　a　restricted　number　that　can　somehow　be　brought　into　existence？　Clearly　we　have　not　a　glimmering　of　how　to　determine　which　laws　of　Nature　are　〃possible〃　and　which　are　not。　Nor　do　we　have　more　than　the　most　rudimentary　notion　of　what　correlations　of　natural　laws　are　〃permitted。〃

For　example；　Newton's　universal　law　of　gravitation　specifies　that　the　mutual　gravitational　force　attracting　two　bodies　towards　each　other　is　inversely　proportional　to　the　square　of　how　far　they　are　apart。　You　move　twice　as　far　from　the　center　of　the　Earth　and　you　weigh　a　quarter　as　much；　ten　times　farther　and　you　weigh　only　a　hundredth　of　your　ordinary　weight；　etc。　It　is　this　inverse　square　law　that　permits　the　exquisite　circular　and　elliptical　orbits　of　planets　around　the　Sun；　and　moons　around　the　planets—as　well　as　the　precision　trajectories　of　our　interplanetary　spacecraft。　If　r　is　the　distance　between　the　centers　of　two　masses；