pale blue dot -carl sagan-第10章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


jectories　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　firmly　from　well…established　theories—of　quantum　mechanics　or　gravitation；　say—we　could　not　be　sure　that　there　weren't　better　theories　that　predict　no　alternative　universes。　Until　that　time　es；　if　it　ever　does；　it　seems　to　me　premature　to　put　faith　in　the　Anthropic　Principle　as　an　argument　for　human　centrality　or　uniqueness。

Finally；　even　if　the　Universe　were　intentionally　created　to　allow　for　the　emergence　of　life　or　intelligence；　other　beings　may　exist　on　countless　worlds。　If　so；　it　would　be　cold　fort　to　anthropocentrists　that　we　inhabit　one　of　the　few　universes　that　allow　life　and　intelligence。

There　is　something　stunningly　narrow　about　how　the　Anthropic　Principle　is　phrased。　Yes；　only　certain　laws　and　constants　of　nature　are　consistent　with　our　kind　of　life。　But　essentially　the　same　laws　and　constants　are　required　to　make　a　rock。　So　why　not　talk　about　a　Universe　designed　so　rocks　could　one　day　e　to　be；　and　strong　and　weak　Lithic　Principles？　If　stones　could　philosophize；　I　imagine　Lithic　Principles　would　be　at　the　intellectual　frontiers。

There　are　cosmological　models　being　formulated　today　in　which　even　the　entire　Universe　is　nothing　special。　Andrei　Linde；　formerly　of　the　Lebedev　Physical　Institute　in　Moscow　and　now　at　Stanford　University；　has　incorporated　current　understanding　of　the　strong　and　weak　nuclear　forces　and　quantum　physics　into　a　new　cosmological　model。　Linde　envisions　a　vast　Cosmos；　much　larger　than　our　Universe—perhaps　extending　to　infinity　both　in　space　and　time—not　the　paltry　15　billion　light…years　or　so　in　radius　and　15　billion　years　in　age　which　are　the　usual　understanding。　In　this　Cosmos　there　is；　as　here；　a　kind　of　quantum　fluff　in　which　tiny　structures—　much　smaller　than　an　electron—are　everywhere　forming；　reshaping；　and　dissipating；　in　which；　as　here；　fluctuations　in　absolutely　empty　space　create　pairs　of　elementary　particles—an　electron　and　a　positron；　for　example。　In　the　froth　of　quantum　bubbles；　the　vast　majority　remain　submicroscopic。　But　a　tiny　fraction　inflate；　grow；　and　achieve　respectable　universehood。　They　are　so　far　away　from　us；　though—much　farther　than　the　15　billion　light…years　that　is　the　conventional　scale　of　our　universe—that；　if　they　exist；　they　appear　to　be　wholly　inaccessible　and　undetectable。

Most　of　these　other　universes　reach　a　maximum　size　and　then　collapse；　contract　to　a　point；　and　disappear　forever。　Others　may　oscillate。　Still　others　may　expand　without　limit。　In　different　universes　there　will　be　different　laws　of　nature。　We　live；　Linde　argues；　in　one　such　universe—one　in　which　the　physics　is　congenial　for　growth；　inflation；　expansion；　galaxies；　stars；　worlds；　life。　We　imagine　our　universe　to　be　unique；　but　it　is　one　of　an　immense　number—perhaps　an　infinite　number—of　equally　valid；　equally　independent；　equally　isolated　universes。　There　will　be　life　in　some；　and　not　in　others。　In　this　view　the　observable　Universe　is　just　a　newly　formed　backwater　of　a　much　vaster；　infinitely　old；　and　wholly　unobservable　Cosmos。　If　something　like　this　is　right；　even　our　residual　pride；　pallid　as　it　must　be；　of　living　in　the　only　universe　is　denied　to　us。

Maybe　someday；　despite　current　evidence；　a　means　will　be　devised　to　peer　into　adjacent　universes；　sporting　very　different　laws　of　nature；　and　we　will　see　what　else　is　possible。　Or　perhaps　inhabitants　of　adjacent　universes　can　peer　into　ours。　Of　course；　in　such　speculations　we　have　far　exceeded　the　bounds　of　knowledge。　But　if　something　like　Linde's　Cosmos　is　true；　there　is—amazingly—still　another　devastating　deprovincialization　awaiting　us。*

For　such　ideas；　words　tend　to　fail　us。　A　German　locution　for　Universe　is　＇dad　911which　makes　the　inclusiveness　quite　unmistakable。　We　might　say　that　our　universe　is　but　one　in　a　〃Multiverse；〃　but　I　prefer　to　use　〃Cosmos〃　for　everything　and　〃Universe〃　for　the　only　one　we　can　know　about。

Our　powers　are　far　from　adequate　to　be　creating　universes　anytime　soon。　Strong　Anthropic　Principle　ideas　are　not　amenable　to　proof　（although　Linde's　cosmology　does　have　some　testable　features）。　Extraterrestrial　life　aside；　if　self…congratulatory　pretensions　to　centrality　have　now　retreated　to　such　bastions　impervious　to　experiment；　then　the　sequence　of　scientific　battles　with　human　chauvinism　would　seem　to　have　been；　at　least　largely；　won。



THE　LONG…STANDING　VIEW；　as　summarized　by　the　philosopher　Immanuel　Kant；　that　〃without　man　。　。　。　the　whole　of　creation　would　be　a　mere　wilderness；　a　thing　in　vain；　and　have　no　final　end〃　is　revealed　to　be　self…indulgent　folly。　A　Principle　of　Mediocrity　seems　to　apply　to　all　our　circumstances。　We　could　not　have　known　beforehand　that　the　evidence　would　be；　so　repeatedly　and　thoroughly；　inpatible　with　the　proposition　that　human　beings　are　at　center　stage　in　the　Universe。　But　most　of　the　debates　have　now　been　settled　decisively　in　favor　of　a　position　that；　however　painful；　can　be　encapsulated　in　a　single　sentence：　We　have　not　been　given　the　lead　in　the　cosmic　drama。

Perhaps　someone　else　has。　Perhaps　no　one　else　has。　In　either　case；　we　have　good　reason　for　hu