万物简史英文版_比尔·布莱森-第25章

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ertainly　never　hearda　shot　fired　in　anger。）in　1919；　now　aged　thirty；　he　moved　to　california　and　took　up　a　position　at　the　mountwilson　observatory　near　los　angeles。　swiftly；　and　more　than　a　little　unexpectedly；　hebecame　the　most　outstanding　astronomer　of　the　twentieth　century。

it　is　worth　pausing　for　a　moment　to　consider　just　how　little　was　known　of　the　cosmos　at　thistime。　astronomers　today　believe　there　are　perhaps　140　billion　galaxies　in　the　visible　universe。

that鈥檚　a　huge　number；　much　bigger　than　merely　saying　it　would　lead　you　to　suppose。　ifgalaxies　were　frozen　peas；　it　would　be　enough　to　fill　a　large　auditorium鈥攖he　old　bostongarden；　say；　or　the　royal　albert　hall。　（an　astrophysicist　named　bruce　gregory　has　actuallyputed　this。）　in　1919；　when　hubble　first　put　his　head　to　the　eyepiece；　the　number　of　thesegalaxies　that　were　known　to　us　was　exactly　one：　the　milky　way。　everything　else　was　thoughtto　be　either　part　of　the　milky　way　itself　or　one　of　many　distant；　peripheral　puffs　of　gas。

hubble　quickly　demonstrated　how　wrong　that　belief　was。

over　the　next　decade；　hubble　tackled　two　of　the　most　fundamental　questions　of　theuniverse：　how　old　is　it；　and　how　big？　to　answer　both　it　is　necessary　to　know　two　things鈥攈owfar　away　certain　galaxies　are　and　how　fast　they　are　flying　away　from　us　（what　is　known　astheir　recessional　velocity）。　the　red　shift　gives　the　speed　at　which　galaxies　are　retiring；　butdoesn鈥檛　tell　us　how　far　away　they　are　to　begin　with。　for　that　you　need　what　are　known　as鈥渟tandard　candles鈥濃�攕tars　whose　brightness　can　be　reliably　calculated　and　used　asbenchmarks　to　measure　the　brightness　（and　hence　relative　distance）　of　other　stars。

hubble鈥檚　luck　was　to　e　along　soon　after　an　ingenious　woman　named　henrietta　swanleavitt　had　figured　out　a　way　to　do　so。　leavitt　worked　at　the　harvard　college　observatory　asa　puter；　as　they　were　known。　puters　spent　their　lives　studying　photographic　plates　ofstars　and　making　putations鈥攈ence　the　name。　it　was　little　more　than　drudgery　by　anothername；　but　it　was　as　close　as　women　could　get　to　real　astronomy　at　harvard鈥攐r　indeed　prettymuch　anywhere鈥攊n　those　days。　the　system；　however　unfair；　did　have　certain　unexpectedbenefits：　it　meant　that　half　the　finest　minds　available　were　directed　to　work　that　wouldotherwise　have　attracted　little　reflective　attention；　and　it　ensured　that　women　ended　up　with　anappreciation　of　the　fine　structure　of　the　cosmos　that　often　eluded　their　male　counterparts。

one　harvard　puter；　annie　jump　cannon；　used　her　repetitive　acquaintance　with　thestars　to　devise　a　system　of　stellar　classifications　so　practical　that　it　is　still　in　use　today。

leavitt鈥檚　contribution　was　even　more　profound。　she　noticed　that　a　type　of　star　known　as　acepheid　variable　（after　the　constellation　cepheus；　where　it　first　was　identified）　pulsated　witha　regular　rhythm鈥攁　kind　of　stellar　heartbeat。　cepheids　are　quite　rare；　but　at　least　one　of　themis　well　known　to　most　of　us。　polaris；　the　pole　star；　is　a　cepheid。

we　now　know　that　cepheids　throb　as　they　do　because　they　are　elderly　stars　that　havemoved　past　their　鈥渕ain　sequence　phase；鈥潯�in　the　parlance　of　astronomers；　and　bee　redgiants。　the　chemistry　of　red　giants　is　a　little　weighty　for　our　purposes　here　（it　requires　anappreciation　for　the　properties　of　singly　ionized　helium　atoms；　among　quite　a　lot　else）；　but　putsimply　it　means　that　they　burn　their　remaining　fuel　in　a　way　that　produces　a　very　rhythmic；very　reliable　brightening　and　dimming。　leavitt鈥檚　genius　was　to　realize　that　by　paring　therelative　magnitudes　of　cepheids　at　different　points　in　the　sky　you　could　work　out　where　theywere　in　relation　to　each　other。　they　could　be　used　as　鈥渟tandard　candles鈥濃�攁　term　she　coinedand　still　in　universal　use。　the　method　provided　only　relative　distances；　not　absolute　distances；but　even　so　it　was　the　first　time　that　anyone　had　e　up　with　a　usable　way　to　measure　thelarge…scale　universe。

（just　to　put　these　insights　into　perspective；　it　is　perhaps　worth　noting　that　at　the　time　leavittand　cannon　were　inferring　fundamental　properties　of　the　cosmos　from　dim　smudges　onphotographic　plates；　the　harvard　astronomer　william　h。　pickering；　who　could　of　course　peerinto　a　first…class　telescope　as　often　as　he　wanted；　was　developing　his　seminal　theory　that　darkpatches　on　the　moon　were　caused　by　swarms　of　seasonally　migrating　insects。）bining　leavitt鈥檚　cosmic　yardstick　with　vesto　slipher鈥檚　handy　red　shifts；　edwin　hubblenow　began　to　measure　selected　points　in　space　with　a　fresh　eye。　in　1923　he　showed　that　a　puffof　distant　gossamer　in　the　andromeda　constellation　known　as　m31　wasn鈥檛　a　gas　cloud　at　allbut　a　blaze　of　stars；　a　galaxy　in　its　own　right；　a　hundred　thousand　light…years　across　and　atleast　nine　hundred　thousand　light…years　away。　the　universe　was　vaster鈥攙astly　vaster鈥攖hananyone　had　ever　supposed。　in　1924　he　produced　a　landmark　paper；　鈥渃epheids　in　spiralnebulae鈥潯。╪ebulae；from　the　latin　for　鈥渃louds；鈥潯�was　his　word　for　galaxies）；　showing　that　theuniverse　consisted　not　just　of　the　milky　way　but　of　lots　of　independent　galaxies鈥斺�渋slanduniverses鈥濃�攎any　of　them　bigger　than　the　milky　way　and　much　more　distant。

this　finding　alone　would　have　ensured　hubble鈥檚　reputation；　but　he　now　turned　to　thequestion　of　working　out　just　how　much　vaster　the　universe　was；　and　made　an　even　morestriking　discovery。　hubble　began　to　measure　the　spectra　of　distant　galaxies鈥攖he　business　thatslipher　had　begun　in　arizona。　using　mount　wilson鈥檚　new　hundred…inch　hooker　telescopeand　some　clever　inferences；　he　worked　out　that　all　the　galaxies　in　the　sky　（except　for　our　ownlocal　cluster）　are　moving　away　from　us。　moreover；　their　speed　and　distance　were　neatlyproportional：　the　further　away　the　galaxy；　the　faster　it　was　moving。

this　was　truly　startling。　the　universe　was　expanding；　swiftly　and　evenly　in　all　directions。　itdidn鈥檛　take　a　huge　amount　of　imagination　to　read　backwards　from　this　and　realize　that　it　musttherefore　have　started　from　some　central　point。　far　from　being　the　stable；　fixed；　eternal　voidthat　everyone　had　always　assumed；　this　was　a　universe　that　had　a　beginning。　it　mighttherefore　also　have　an　end。

the　wonder；　as　stephen　hawking　has　noted；　is　that　no　one　had　hit　on　the　idea　of　theexpanding　universe　before。　a　static　universe；　as　should　have　been　obvious　to　newton　andevery　thinking　astronomer　since；　would　collapse　in　upon　itself。　there　was　also　the　problemthat　if　stars　had　been　burning　indefinitely　in　a　static　universe　they鈥檇　have　made　the　wholeintolerably　hot鈥攃ertainly　much　too　hot　for　the　likes　of　us。　an　expanding　universe　resolvedmuch　of　this　at　a　stroke。

hubble　was　a　much　better　observer　than　a　thinker　and　didn鈥檛　immediately　appreciate　thefull　implications　of　what　he　had　found。　partly　this　was　because　he　was　woefully　ignorant　ofeinstein鈥檚　general　theory　of　relativity。　this　was　quite　remarkable　because；　for　one　thing；einstein　and　his　theory　were　world　famous　by　now。　moreover；　in　1929　albert　michelson鈥攏ow　in　his　twilight　years　but　still　one　of　the　world鈥檚　most　alert　and　esteemed　scientists鈥攁ccepted　a　position　at　mount　wilson　to　measure　the　velocity　of　light　with　his　trustyinterferometer；　and　must　surely　have　at　least　mentioned　to　him　the　applicability　of　einstein鈥檚theory　to　his　own　findings。

at　all　events；　hubble　failed　to　make　theoretical　hay　when　the　chance　was　there。　instead；　itwas　left　to　a　belgian　priest…scholar　（with　a　ph。d。　from　mit）　named　georges　lema？tre　tobring　together　the　two　strands　in　his　own　鈥渇ireworks　theory；鈥潯�which　suggested　that　theuniverse　began　as　a　geometrical　point；　a　鈥減rimeval　atom；鈥潯�which　burst　into　glory　and　hadbeen　moving　apart　ever　since。　it　was　an　idea　that　very　neatly　anticipated　the　modernconception　of　the　big　bang　but　was　so　far　ahead　of　its　time　that　lema？tre　seldom　gets　morethan　the　sentence　or　two　that　we　have　given　him　here。　the　world　would　need　additionaldecades；　and　the　inadvertent　discovery　of　cosmic　background　radiation　by　penzias　and　wilsonat　their　hissing　antenna　in　new　jersey；　before　the　big　bang　would　begin　to　move　frominteresting　idea　to　established　theory。

neither　hubble　nor　einstein　would　be　much　of　a　part　of　that　big　story。　though　no　onewould　have　guessed　it　at　the　time；　both　men　had　done　about　as　much　as　they　were　ever　goingto　do。

in　1936　hubble　produced　a　popular　book　called　the　realm　of　the　nebulae；　whichexplained　in　flattering　style　his　own　considerable　achievements。　here　at　last　he　showed　thathe　had　acquainted　himself　with　einstein鈥檚　theory鈥攗p　to　a　point　anyway：　he　gave　it　four　pagesout　of　about　two　hundred。

hubble　died　of　a　heart　attack　in　1953。　one　last　small　oddity　awaited　him。　for　reasonscloaked　in　mystery；　his　wife　declined　to　have　a　funeral　and　never　revealed　what　she　did　withhis　body。　half　a　century　later　the　whereabouts　of　the　century鈥檚　greatest　astronomer　remainunknown。　for　a　memorial　you　must　look　to　the　sky　and　the　hubble　space　telescope；launched　in　1990　and　named　in　his　honor。

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9　　　　THE　MIGHTY　ATOM

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while　einstein　and　hubble　were　productively　unraveling　the　large…scale　structure　ofthe　cosmos；　others　were　struggling　to　understand　something　closer　to　hand　but　in　its　way　justas　remote：　the　tiny　and　ever…　mysterious　atom。

the　great　caltech　physicist　richard　feynman　once　observed　that　if　you　had　to　reducescientific　history　to　one　important　statement　it　would　be　鈥渁ll　things　are　made　of　atoms。鈥潯�theyare　everywhere　and　they　constitute　every　thing。　look　around　you。　it　is　all　atoms。　not　just　thesolid　things　like　walls　and　tables　and　sofas；　but　the　air　in　between。　and　they　are　there　innumbers　that　you　really　cannot　conceive。

the　basic　working　arrangement　of　atoms　is　the　molecule　（from　the　latin　for　鈥渓ittle　mass鈥潱�。

a　molecule　is　simply　two　or　more　atoms　working　together　in　a　more　or　less　stablearrangement：　add　two　atoms　of　hydrogen　to　one　of　oxygen　and　you　have　a　molecule　of　water。

chemists　tend　to　think　in　terms　of　molecules　rather　than　elements　in　much　the　way　thatwriters　tend　to　think　in　terms　of　words　and　not　letters；　so　it　is　molecules　they　count；　and　theseare　numerous　to　say　the　least。　at　sea　level；　at　a　temperature　of　32　degrees　fahrenheit；　onecubic　centimeter　of　air　（that　is；　a　space　about　the　size　of　a　sugar　cube）　will　contain　45　billionbillion　molecules。　and　they　are　in　every　single　cubic　centimeter　you　see　around　you。　thinkhow　many　cubic　centimeters　there　are　in　the　world　outside　your　window鈥攈ow　many　sugarcubes　it　would　take　to　fill　that　view。　then　think　how　many　it　would　take　to　build　a　universe。

atoms；　in　short；　are　very　abundant。

they　are　also　fantastically　durable。　because　they　are　so　long　lived；　atoms　really　get　around。

every　atom　you　possess　has　almost　certainly　passed　through　several　stars　and　been　part　ofmillions　of　organisms　on　its　way　to　being　you。　we　are　each　so　atomically　numerous　andso　vigorously　recycled　at　death　that　a　significant　number　of　our　atoms鈥攗p　to　a　billion　foreach　of　us；　it　has　been　suggested鈥攑robably　once　belonged　to　shakespeare。　a　billion　moreeach　came　from　buddha　and　genghis　khan　and　beethoven；　and　any　other　historical　figureyou　care　to　name。　（the　personages　have　to　be　historical；　apparently；　as　it　takes　the　atom