pale blue dot -carl sagan-第5部分

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　time　dilation　applies　to　watches　and　elementary　particles—and；　presumably；　to　circadian　and　other　rhythms　in　plants；　animals；　and　microbes—but　not　to　human　biological　clocks。　Our　species　has　been　granted；　it　is　suggested；　special　immunity　from　the　laws　of　Nature；　which　must　accordingly　be　able　to　distinguish　deserving　from　undeserving　collections　of　matter。　（In　fact；　the　proof　Einstein　gave　for　special；　relativity　admits　no　such　distinctions。）　The　idea　of　humans　as　exceptions　to　relativity　seems　another　incarnation　of　the　notion　of　special　creation：

Well；　even　if　our　position；　our　epoch；　our　motion；　and　our　world　are　not　unique；　maybe　we　are。　We're　different　from　the　other　animals。　We're　specially　created。　The　particular　devotion　of　the　Creator　of　the　Universe　is　evident　in　us。　This　position　was　passionately　defended　on　religious　and　other　grounds。　But　in　the　middle　nineteenth　century　Charles　Darwin　showed　convincingly　how　one　species　can　evolve　into　another　by　entirely　natural　processes；　which　e　down　to　the　heartless　business　of　Nature　saving　the　heredities　that　work　and　rejecting　those　that　don't。　〃Man　in　his　arrogance　thinks　himself　a　great　work　worthy　＇of＇　the　interposition　of　a　deity；〃　Darwin　wrote　telegraphically　in　his　notebook。　〃More　humble　and　I　think　truer　to　consider　him　created　from　animals。〃　The　profound　and　intimate　connections　of　humans　with　the　other　life　forms；　on　Earth　have　been　pellingly　demonstrated　in　the　late　twentieth　century　by　the　new　science　of　molecular　biology。



IN　EACH　AGE　the　self…congratulatory　chauvinisms　are　challenged　in　yet　another　arena　of　scientific　debate—in　this　century；　for　example；　in　attempts　to　understand　the　nature　of　human　sexuality；　the　existence　of　the　unconscious　mind；　and　the　fact　that　many　psychiatric　illnesses　and　character　〃defects〃　have　a　molecular　origin。　But　also：

Well；　even　if　we're　closely　related　to　some　of　the　other　animals；　we're　different—not　just　in　degree；　but　in　kind—on　what　really　matters：　reasoning；　selfconsciousness；　tool　making；　ethics；　altruism；　religion；　language；　nobility　of　character。　While　humans；　like　all　animals；　have　traits　that　set　them　apart—otherwise；　how　could　we　distinguish　one　species　from　another？—human　uniqueness　has　been　exaggerated；　sometimes　grossly　so。　Chimps　reason；　are　self…conscious；　make　tools；　show　devotion；　and　so　on。　Chimps　and　humans　have　99。6　percent　of　their　active　genes　in　mon。　（Ann　Druyan　and　I　run　through　the　evidence　in　our　book　Shadows　of　Forgotten　Ancestors。）

In　popular　culture；　the　very　opposite　position　is　also　embraced；　although　it　too　is　driven　by　human　chauvinism　（plus　a　failure　of　the　imagination）：　Children's　stories　and　cartoons　make　animals　dress　in　clothes；　live　in　houses；　use　knives　and　forks；　and　speak。　The　three　bears　sleep　in　beds。　The　owl　and　the　pussycat　go　to　sea　in　a　beautiful　pea…green　boat。　Dinosaur　mothers　cuddle　their　young。　Pelicans　deliver　the　mail。　Dogs　drive　cars。　A　worm　catches　a　thief。　Pets　have　human　names。　Dolls；　nutcrackers；　cups；　and　saucers　dance　and　have　opinions。　The　dish　runs　away　with　the　spoon。　In　the　Thomas　the　Tank　Engine　series；　we　even　have　anthropomorphic　lootives　and　railway　cars；　charmingly　portrayed。　No　matter　what　we're　thinking　about；　animate　or　inanimate；　we　tend　to　invest　it　with　human　traits。　We　can't　help　ourselves。　The　images　e　readily　to　mind。　Children　are　clearly　fond　of　them。

When　we　talk　about　a　〃threatening〃　sky；　a　〃troubled〃　sea　diamonds　〃resisting〃　being　scratched；　the　Earth　〃attracting〃　passing　asteroid；　or　an　atom　being　〃excited；〃　we　are　again　drawn　to　a　kind　of　animist　worldview。　We　reify。　Some　ancient　level　of　our　thinking　endows　inanimate　Nature　with　life；　passions；　and　forethought。

The　notion　that　the　Earth　is　self…aware　has　lately　been　growing　at　the　fringes　of　the　〃Gaia〃　hypothesis。　But　this　was　monplace　belief　of　both　the　ancient　Greeks　and　the　earl　Christians。　Origen　wondered　whether　〃the　earth　also；　according　to　its　own　nature；　is　accountable　for　some　sin。〃　A　host　of　ancient　scholars　thought　the　stars　alive。　This　was　also　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；　we　say　that　the　gravitational　force　varies　as　1/r2。

But　if　this　exponent　were　different—if　the　gravitational　law　were　1/r4；　say；　rather　than　1/r2　—then　the　orbits　would　not　close；　over　billions　of　revolutions；　the　planets　would　spiral　in　and　be　consumed　in　the　fiery　depths　of　the　Sun；　or　spiral　out　and　be　lost　to　interstellar　space。　If　the　Universe　were　constructed　with　an　inverse　fourth　power　law　rather　than　an　inverse　square　law；　soon　there　would　be　no　planets　for　living　beings　to　inhabit。

So　of　all　the　possible　gravitational　force　laws；　why　are　we　so　lucky　as　to　live　in　a　universe　sporting　a　law　consistent　with　life？　First　of　course；　we're　so　〃lucky；〃　because　if　we　weren't；　we　wouldn't　be　here　to　ask　the　question。　It　is　no　mystery　that　inquisitive　beings　who　evolve　on　planets　can　be　found　only　in　universes　that　admit　planets。　Second；　the　inverse　square　law　is　not　is　the　only　one　consistent　with　stability　over　billions　of　years。　Any　power　law　less　steep　than　1/r3　（1/r2。99　or　1/r；　for　example）　will　keep　a　planet　in　the　vicinity　of　a　circular　orbit　even　if　it's　given　a　shove。　We　have　a　tendency　to　overlook　the　possibility　that　other　conceivable　laws　of　Nature　might　also　be　consistent　with　life。

But　there's　a　further　point：　It's　not　arbitrary　that　we　have　an　inverse　square　law　of　gravitation。　When　Newton's　theory　is　understood　in　terms　of　the　more　enpassing　general　theory　of　relativity；　we　recognize　that　the　exponent　of　the　gravity　law　is　2　because　the　number　of　physical　dimensions　we　live　in　is　3。　All　gravity　laws　aren't　available；　free　for　a　Creator's　choosing。　Even　given　an　infinite　number　of　three…dimensional　universes　for　some　great　god　to　tinker　with；　the　gravity　law　would　always　lave　to　be　the　law　of　the　inverse　square。　Newtonian　gravity；　we　might　say；　is　not　a　contingent　facet　of　our　universe；　but　a　necessary　one。

In　general　relativity；　gravity　is　due　to　the　dimensionality　and　curvature　of　space。　When　we　talk　about　gravity　we　are　talking　about　local　dimples　in　space…time。　This　is　by　no　means　obvious　and　even　affronts　monsense　notions。　But　when　examined　deeply；　the　ideas　of　gravity　and　mass　are　not　separate　matters；　but　ramifications　of　the　underlying　geometry　of　space…time。

I　wonder　if　something　like　this　doesn't　apply　generally　to　all　anthropic　hypotheses。　The　laws　or　physical　constants　on　which　our　lives　depend　turn　out　to　be　members　of　a　class；　perhaps　even　a　vast　class；　of　other　laws　and　other　physical　constants—but　some　of　these　are　also　patible　with　a　kind　of　life。　Often　we　do　not　（or　cannot）　work　through　what　those　other　universes　allow。　Beyond　that；　not　every　arbitrary　choice　of　a　law　of　Nature　or　a　physical　constant　may　be　available；　even　to　a　maker　of　universes。　Our　understanding　of　which　laws　of　Nature　and　which　physical　constants　are　up　for　grabs　is　fragmentary　at　best。

Moreover；　we　have　no　access　to　any　of　those　putative　alternative　universes。　We　have　no　experimental　method　by　which　anthropic　hypotheses　may　be　tested。　Even　if　the　existence　of　such　universes　were　to　follow　firm