A Short History of Nearly Everything-第5章

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an　suppose。”

the　analogy　that　is　usually　given　for　explaining　the　curvature　of　space　is　to　try　to　imaginesomeone　from　a　universe　of　flat　surfaces；　who　had　never　seen　a　sphere；　being　brought　toearth。　no　matter　how　far　he　roamed　across　the　planet’s　surface；　he　would　never　find　an　edge。

he　might　eventually　return　to　the　spot　where　he　had　started；　and　would　of　course　be　utterlyconfounded　to　explain　how　that　had　happened。　well；　we　are　in　the　same　position　in　space　asour　puzzled　flatlander；　only　we　are　flummoxed　by　a　higher　dimension。

just　as　there　is　no　place　where　you　can　find　the　edge　of　the　universe；　so　there　is　no　placewhere　you　can　stand　at　the　center　and　say：　“this　is　where　it　all　began。　this　is　the　centermostpoint　of　it　all。”　we　are　all　at　the　center　of　it　all。　actually；　we　don’t　know　that　for　sure；　wecan’t　prove　it　mathematically。　scientists　just　assume　that　we　can’t　really　be　the　center　of　theuniverse—think　what　that　would　imply—but　that　the　phenomenon　must　be　the　same　for　allobservers　in　all　places。　still；　we　don’t　actually　know。

for　us；　the　universe　goes　only　as　far　as　light　has　traveled　in　the　billions　of　years　since　theuniverse　was　formed。　this　visible　universe—the　universe　we　know　and　can　talk　about—is　amillion　million　million　million　（that’s　1；000；000；000；000；000；000；000；000）　miles　across。　butaccording　to　most　theories　the　universe　at　large—the　meta…universe；　as　it　is　sometimescalled—is　vastly　roomier　still。　according　to　rees；　the　number　of　light…years　to　the　edge　ofthis　larger；　unseen　universe　would　be　written　not　“with　ten　zeroes；　not　even　with　a　hundred；but　with　millions。”　in　short；　there’s　more　space　than　you　can　imagine　already　without　going　tothe　trouble　of　trying　to　envision　some　additional　beyond。

for　a　long　time　the　big　bang　theory　had　one　gaping　hole　that　troubled　a　lot　of　people—namely　that　it　couldn’t　begin　to　explain　how　we　got　here。　although　98　percent　of　all　thematter　that　exists　was　created　with　the　big　bang；　that　matter　consisted　exclusively　of　lightgases：　the　helium；　hydrogen；　and　lithium　that　we　mentioned　earlier。　not　one　particle　of　theheavy　stuff　so　vital　to　our　own　being—carbon；　nitrogen；　oxygen；　and　all　the　rest—emergedfrom　the　gaseous　brew　of　creation。　but—and　here’s　the　troubling　point—to　forge　these　heavyelements；　you　need　the　kind　of　heat　and　energy　of　a　big　bang。　yet　there　has　been　only　onebig　bang　and　it　didn’t　produce　them。　so　where　did　they　e　from？

interestingly；　the　man　who　found　the　answer　to　that　question　was　a　cosmologist　whoheartily　despised　the　big　bang　as　a　theory　and　coined　the　term　“big　bang”　sarcastically；　as　away　of　mocking　it。　we’ll　get　to　him　shortly；　but　before　we　turn　to　the　question　of　how　we　gothere；　it　might　be　worth　taking　a　few　minutes　to　consider　just　where　exactly　“here”　is。

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2　　WELE　TO　THE　SOLAR　SYSTEMAS


tronomers　these　days　can　do　the　most　amazing　things。　if　someone　struck　a　matchon　the　moon；　they　could　spot　the　flare。　from　the　tiniest　throbs　and　wobbles　of　distant　starsthey　can　infer　the　size　and　character　and　even　potential　habitability　of　planets　much　tooremote　to　be　seen—planets　so　distant　that　it　would　take　us　half　a　million　years　in　a　spaceshipto　get　there。　with　their　radio　telescopes　they　can　capture　wisps　of　radiation　so　preposterouslyfaint　that　the　total　amount　of　energy　collected　from　outside　the　solar　system　by　all　of　themtogether　since　collecting　began　（in　1951）　is　“less　than　the　energy　of　a　single　snowflakestriking　the　ground；”　in　the　words　of　carl　sagan。

in　short；　there　isn’t　a　great　deal　that　goes　on　in　the　universe　that　astronomers　can’t　findwhen　they　have　a　mind　to。　which　is　why　it　is　all　the　more　remarkable　to　reflect　that　until　1978no　one　had　ever　noticed　that　pluto　has　a　moon。　in　the　summer　of　that　year；　a　youngastronomer　named　james　christy　at　the　u。s。　naval　observatory　in　flagstaff；　arizona；　wasmaking　a　routine　examination　of　photographic　images　of　pluto　when　he　saw　that　there　wassomething　there—something　blurry　and　uncertain　but　definitely　other　than　pluto。　consulting　acolleague　named　robert　harrington；　he　concluded　that　what　he　was　looking　at　was　a　moon。

and　it　wasn’t　just　any　moon。　relative　to　the　planet；　it　was　the　biggest　moon　in　the　solarsystem。

this　was　actually　something　of　a　blow　to　pluto’s　status　as　a　planet；　which　had　never　beenterribly　robust　anyway。　since　previously　the　space　occupied　by　the　moon　and　the　spaceoccupied　by　pluto　were　thought　to　be　one　and　the　same；　it　meant　that　pluto　was　much　smallerthan　anyone　had　supposed—smaller　even　than　mercury。　indeed；　seven　moons　in　the　solarsystem；　including　our　own；　are　larger。

now　a　natural　question　is　why　it　took　so　long　for　anyone　to　find　a　moon　in　our　own　solarsystem。　the　answer　is　that　it　is　partly　a　matter　of　where　astronomers　point　their　instrumentsand　partly　a　matter　of　what　their　instruments　are　designed　to　detect；　and　partly　it’s　just　pluto。

mostly　it’s　where　they　point　their　instruments。　in　the　words　of　the　astronomer　clarkchapman：　“most　people　think　that　astronomers　get　out　at　night　in　observatories　and　scan　theskies。　that’s　not　true。　almost　all　the　telescopes　we　have　in　the　world　are　designed　to　peer　atvery　tiny　little　pieces　of　the　sky　way　off　in　the　distance　to　see　a　quasar　or　hunt　for　black　holesor　look　at　a　distant　galaxy。　the　only　real　network　of　telescopes　that　scans　the　skies　has　beendesigned　and　built　by　the　military。”

we　have　been　spoiled　by　artists’　renderings　into　imagining　a　clarity　of　resolution　thatdoesn’t　exist　in　actual　astronomy。　pluto　in　christy’s　photograph　is　faint　and　fuzzy—a　piece　ofcosmic　lint—and　its　moon　is　not　the　romantically　backlit；　crisply　delineated　panion　orbyou　would　get　in　a　national　geographic　painting；　but　rather　just　a　tiny　and　extremelyindistinct　hint　of　additional　fuzziness。　such　was　the　fuzziness；　in　fact；　that　it　took　seven　yearsfor　anyone　to　spot　the　moon　again　and　thus　independently　confirm　its　existence。

one　nice　touch　about　christy’s　discovery　was　that　it　happened　in　flagstaff；　for　it　was　therein　1930　that　pluto　had　been　found　in　the　first　place。　that　seminal　event　in　astronomy　waslargely　to　the　credit　of　the　astronomer　percival　lowell。　lowell；　who　came　from　one　of　theoldest　and　wealthiest　boston　families　（the　one　in　the　famous　ditty　about　boston　being　thehome　of　the　bean　and　the　cod；　where　lowells　spoke　only　to　cabots；　while　cabots　spoke　onlyto　god）；　endowed　the　famous　observatory　that　bears　his　name；　but　is　most　indeliblyremembered　for　his　belief　that　mars　was　covered　with　canals　built　by　industrious　martians　forpurposes　of　conveying　water　from　polar　regions　to　the　dry　but　productive　lands　nearer　theequator。

lowell’s　other　abiding　conviction　was　that　there　existed；　somewhere　out　beyond　neptune；an　undiscovered　ninth　planet；　dubbed　planet　x。　lowell　based　this　belief　on　irregularities　hedetected　in　the　orbits　of　uranus　and　neptune；　and　devoted　the　last　years　of　his　life　to　trying　tofind　the　gassy　giant　he　was　certain　was　out　there。　unfortunately；　he　died　suddenly　in　1916；　atleast　partly　exhausted　by　his　quest；　and　the　search　fell　into　abeyance　while　lowell’s　heirssquabbled　over　his　estate。　however；　in　1929；　partly　as　a　way　of　deflecting　attention　awayfrom　the　mars　canal　saga　（which　by　now　had　bee　a　serious　embarrassment）；　the　lowellobservatory　directors　decided　to　resume　the　search　and　to　that　end　hired　a　young　man　fromkansas　named　clyde　tombaugh。

tombaugh　had　no　formal　training　as　an　astronomer；　but　he　was　diligent　and　he　was　astute；and　after　a　year’s　patient　searching　he　somehow　spotted　pluto；　a　faint　point　of　light　in　aglittery　firmament。　it　was　a　miraculous　find；　and　what　made　it　all　the　more　striking　was　thatthe　observations　on　which　lowell　had　predicted　the　existence　of　a　planet　beyond　neptuneproved　to　be　prehensively　erroneous。　tombaugh　could　see　at　once　that　the　new　planetwas　nothing　like　the　massive　gasball　lowell　had　postulated；　but　any　reservations　he　or　anyoneelse　had　about　the　character　of　the　new　planet　were　soon　swept　aside　in　the　delirium　thatattended　almost　any　big　news　story　in　that　easily　excited　age。　this　was　the　first　american…discovered　planet；　and　no　one　was　going　to　be　distracted　by　the　thought　that　it　was　really　justa　distant　icy　dot。　it　was　named　pluto　at　least　partly　because　the　first　two　letters　made　amonogram　from　lowell’s　initials。　lowell　was　posthumously　hailed　everywhere　as　a　genius　ofthe　first　order；　and　tombaugh　was　largely　forgotten；　except　among　planetary　astronomers；who　tend　to　revere　him。

a　few　astronomers　continue　to　think　there　may　be　a　planet　x　out　there—a　real　whopper；perhaps　as　much　as　ten　times　the　size　of　jupiter；　but　so　far　out　as　to　be　invisible　to　us。　（itwould　receive　so　little　sunlight　that　it　would　have　almost　none　to　reflect。）　the　idea　is　that　itwouldn’t　be　a　conventional　planet　like　jupiter　or　saturn—it’s　much　too　far　away　for　that；we’re　talking　perhaps　4。5　trillion　miles—but　more　like　a　sun　that　never　quite　made　it。　moststar　systems　in　the　cosmos　are　binary　（double…starred）；　which　makes　our　solitary　sun　a　slightoddity。

as　for　pluto　itself；　nobody　is　quite　sure　how　big　it　is；　or　what　it　is　made　of；　what　kind　ofatmosphere　it　has；　or　even　what　it　really　is。　a　lot　of