pale blue dot -carl sagan-第73章

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eadly　purpose；　and　moreover　a　species　that　until　only　recently　was　convinced　that　the　Universe　was　made　for　its　sole　benefit—are　we　to　venture　out　into　space；　move　worlds；　reengineer　planets；　spread　to　neighboring　star　systems？

*　A　value　that　nicely　approximates　modern　estimates　of　the　number　of　planets　orbiting　stars　in　the　Milky　Way　Galaxy。

I　do　not　imagine　that　it　is　precisely　we；　with　our　present　customs　and　social　conventions；　who　will　be　out　there。　If　we　continue　to　accumulate　only　power　and　not　wisdom；　we　will　surely　destroy　ourselves。　Our　very　existence　in　that　distant　time　requires　that　we　will　have　changed　our　institutions　and　ourselves。　How　can　I　dare　to　guess　about　humans　in　the　far　future？　It　is；　I　think；　only　a　matter　of　natural　selection。　If　we　bee　even　slightly　more　violent；　shortsighted；　ignorant；　and　selfish　than　we　are　now；　almost　certainly　we　will　have　no　future。

If　you're　young；　it's　just　possible　that　we　will　be　taking　our　first　steps　on　near…Earth　asteroids　and　Mars　during　your　lifetime。　To　spread　out　to　the　moons　of　the　Jovian　planets　and　the　Kuiper　et　Belt　will　take　many　generations　more。　The　Oort　Cloud　will　require　much　longer　still。　By　the　time　we're　ready　to　settle　even　the　nearest　other　planetary　systems；　we　will　have　changed。　The　simple　passage　of　so　many　generations　will　have　changed　us。　The　different　circumstances　we　will　be　living　under　will　have　changed　us。　Prostheses　and　genetic　engineering　will　have　changed　us。　Necessity　will　have　changed　us。　We're　an　adaptable　species。

It　will　not　be　we　who　reach　Alpha　Centauri　and　the　other　nearby　stars。　It　will　be　a　species　very　like　us；　but　with　more　of　our　strengths　and　fewer　of　our　weaknesses；　a　species　returned　to　circumstances　more　like　those　for　which　it　was　originally　evolved；　more　confident；　farseeing；　capable；　and　prudent—the　sorts　of　beings　we　would　want　to　represent　us　in　a　Universe　that；　for　all　we　know；　is　filled　with　species　much　older；　much　more　powerful；　and　very　different。

The　vast　distances　that　separate　the　stars　are　providential。　Beings　and　worlds　are　quarantined　from　one　another。　The　quarantine　is　lifted　only　for　those　with　sufficient　self…knowledge　and　judgment　to　have　safely　traveled　from　star　to　star。



ON　IMMENSE　TIMESCALES；　in　hundreds　of　millions　to　billions　of　years；　the　centers　of　galaxies　explode。　We　see；　scattered　across　deep　space；　galaxies　with　〃active　nuclei；〃　quasars；　galaxies　distorted　by　collisions；　their　spiral　arms　disrupted；　star　systems　blasted　with　radiation　or　gobbled　up　by　black　holes—and　we　gather　that　on　such　timescales　even　interstellar　space；　even　galaxies　may　not　be　safe。

There　is　a　halo　of　dark　matter　surrounding　the　Milky　Way；　extending　perhaps　halfway　to　the　distance　of　the　next　spiral　galaxy　（M31　in　the　constellation　Andromeda；　which　also　contains　hundreds　of　billions　of　stars）。　We　do　not　know　what　this　dark　matter　is；　or　how　it　is　arranged—but　some*　of　it　may　be　in　worlds　untethered　to　individual　stars。　If　so；　our　descendants　of　the　remote　future　will　have　an　opportunity；　over　unimaginable　intervals　of　time；　to　bee　established　in　intergalactic　space；　and　to　tiptoe　to　other　galaxies。

*　Most　of　it　may　be　in　〃nonbaryonic〃　matter；　not　made　of　our　familiar　protons　and　neutrons；　and　not　anti…matter　either。　Over　90　percent　of　the　mass　of　the　Universe　seems　to　be　in　this　dark；　quintessential；　deeply　mysterious　stuff　wholly　unknown　on　Earth。　Perhaps　we　will　one　day　not　only　understand　it；　but　also　find　a　use　for　it。

But　on　the　timescale　for　populating　our　galaxy；　if　not　long　before；　we　must　ask：　How　immutable　is　this　longing　for　safety　that　drives　us　outward？　Will　we　one　day　feel　content　with　the　time　our　species　has　had　and　our　successes；　and　willingly　exit　the　cosmic　stage？　Millions　of　years　from　now—probably　much　sooner—we　will　have　made　ourselves　into　something　else。　Even　if　we　do　nothing　intentionally；　the　natural　process　of　mutation　and　selection　will　have　worked　our　extinction　or　evolved　us　into　some　other　species　on　just　such　a　timescale　（if　we　may　judge　by　other　mammals）。　Over　the　typical　lifetime　of　a　mammalian　species；　even　if　we　were　able　to　travel　close　to　the　speed　of　light　and　were　dedicated　to　nothing　else；　we　could　not；　I　think；　explore　even　a　representative　fraction　of　the　Milky　Way　Galaxy。　There's　just　too　much　of　it。　And　beyond　are　a　hundred　billion　galaxies　more。　Will　our　present　motivations　remain　unchanged　over　geological；　much　less　cosmological；　timescales—when　we　ourselves　have　been　transfigured？　In　such　remote　epochs；　we　may　discover　outlets　for　our　ambitions　far　grander　and　more　worthy　than　merely　populating　an　unlimited　number　of　worlds。

Perhaps；　some　scientists　have　imagined；　we　will　one　day　create　new　forms　of　life；　link　minds；　colonize　stars；　reconfigure　galaxies；　or　prevent；　in　a　nearby　volume　of　space；　the　expansion　of　the　Universe。　In　a　1993　article　in　the　journal　Nuclear　Physics；　the　physicist　Andrei　Linde—conceivably；　in　a　playful　mood—suggests　that　laboratory　experiments　（it　would　have　to　be　quite　a　laboratory）　to　create　separate；　closed…off；　expanding　universes　might　ultimately　be　possible。　〃However；〃　he　writes　to　me；　〃I　myself　do　not　know　whether　＇this　suggestion＇　is　simply　a　joke　or　something　else。〃　In　such　a　list　of　projects　for　the　far　future；　we　will　have　no　difficulty　in　recognizing　a　continuing　human　ambition　to　arrogate　powers　once　considered　godlike—or；　in　that　other　more　encouraging　metaphor；　to　plete　the　Creation。



FOR　MANY　PAGES　NOW；　we　have　left　the　realm　of　plausible　conjecture　for　the　heady　intoxication　of　nearly　unconstrained　speculation。　It　is　time　to　return　to　our　own　age。

My　grandfather；　born　before　radio　waves　were　even　a　laboratory　curiosity；　almost　lived　to　see　the　first　artificial　satellite　beeping　down　at　us　from　space。　There　are　people　who　were　born　before　there　was　such　a　thing　as　an　airplane；　and　who　in　old　age　saw　four　ships　launched　to　the　stars。　For　all　our　failings；　despite　our　limitations　and　fallibilities；　we　humans　are　capable　of　greatness。　This　is　true　of　our　science　and　some　areas　of　our　technology；　of　our　art；　music；　literature；　altruism；　and　passion；　and　even；　on　rare　occasion；　of　our　statecraft。　What　new　wonders　undreamt　of　in　our　time　will　we　have　wrought　in　another　generation？　And　another？　How　far　will　our　nomadic　species　have　wandered　by　the　end　of　the　next　century？　And　the　next　millennium？

Two　billion　years　ago　our　ancestors　were　microbes；　a　halfbillion　years　ago；　fish；　a　hundred　million　years　ago；　something　like　mice；　ten　million　years　ago；　arboreal　apes；　and　a　million　years　ago；　proto…humans　puzzling　out　the　taming　of　fire。　Our　evolutionary　lineage　is　marked　by　mastery　of　change。　In　our　time；　the　pace　is　quickening。

When　we　first　venture　to　a　near…Earth　asteroid；　we　will　have　entered　a　habitat　that　may　engage　our　species　forever。　The　first　voyage　of　men　and　women　to　Mars　is　the　key　step　in　transforming　us　into　a　multiplanet　species。　These　events　are　as　momentous　as　the　colonization　of　the　land　by　our　amphibian　ancestors　and　the　descent　from　the　trees　by　our　primate　ancestors。

Fish　with　rudimentary　lungs　and　fins　slightly　adapted　for　walking　must　have　died　in　great　numbers　before　establishing　a　permanent　foothold　on　the　land。　As　the　forests　slowly　receded；　our　upright　apelike　forebears　often　scurried　back　into　the　trees；　fleeing　the　predators　that　stalked　the　savannahs。　The　transitions　were　painful；　took　millions　of　years；　and　were　imperceptible　to　those　involved。　In　our　case　the　transition　occupies　only　a　few　generations；　and　with　only　a　handful　of　lives　lost。　The　pace　is　so　swift　that　we　are　still　barely　able　to　grasp　what　is　happening。

Once　the　first　children　are　born　off　Earth；　once　we　have　bases　and　homesteads　on　asteroids；　ets；　moons；　and　planets；　once　we're　living　off　the　land　and　bringing　up　new　generations　on　other　worlds；　something　will　have　changed　forever　in　human　history。　But　inhabiting　other　worlds　does　not　imply　abandoning　this　one；　any　more　than　the　evolution　of　amphibians　meant　the　end　of　fish。　For　a　very　long　time　only　a　small　fraction　of　us　will　be　out　there。

〃In　modern　Western　society；〃　writes　the　scholar　Charles　Lindholm；

the　erosion　of　tradition　and