A Short History of Nearly Everything-第25章

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coincidentally；　at　about　the　time　that　einstein　was　affixing　a　cosmological　constant　to　histheory；　at　the　lowell　observatory　in　arizona；　an　astronomer　with　the　cheerily　intergalacticname　of　vesto　slipher　（who　was　in　fact　from　indiana）　was　taking　spectrographic　readings　ofdistant　stars　and　discovering　that　they　appeared　to　be　moving　away　from　us。　the　universewasn’t　static。　the　stars　slipher　looked　at　showed　unmistakable　signs　of　a　doppler　shift5—thesame　mechanism　behind　that　distinctive　stretched…out　yee…yummm　sound　cars　make　as　theyflash　past　on　a　racetrack。　the　phenomenon　also　applies　to　light；　and　in　the　case　of　recedinggalaxies　it　is　known　as　a　red　shift　（because　light　moving　away　from　us　shifts　toward　the　redend　of　the　spectrum；　approaching　light　shifts　to　blue）。

slipher　was　the　first　to　notice　this　effect　with　light　and　to　realize　its　potential　importancefor　understanding　the　motions　of　the　cosmos。　unfortunately　no　one　much　noticed　him。　thelowell　observatory；　as　you　will　recall；　was　a　bit　of　an　oddity　thanks　to　percival　lowell’sobsession　with　martian　canals；　which　in　the　1910s　made　it；　in　every　sense；　an　outpost　ofastronomical　endeavor。　slipher　was　unaware　of　einstein’s　theory　of　relativity；　and　the　worldwas　equally　unaware　of　slipher。　so　his　finding　had　no　impact。

glory　instead　would　pass　to　a　large　mass　of　ego　named　edwin　hubble。　hubble　was　born　in1889；　ten　years　after　einstein；　in　a　small　missouri　town　on　the　edge　of　the　ozarks　and　grewup　there　and　in　wheaton；　illinois；　a　suburb　of　chicago。　his　father　was　a　successful　insuranceexecutive；　so　life　was　always　fortable；　and　edwin　enjoyed　a　wealth　of　physicalendowments；　too。　he　was　a　strong　and　gifted　athlete；　charming；　smart；　and　immensely　good…looking—“handsome　almost　to　a　fault；”　in　the　description　of　william　h。　cropper；　“an5named　for　johann　christian　doppler；　an　austrian　physicist；　who　first　noticed　the　effect　in　1842。　briefly；　whathappens　is　that　as　a　moving　object　approaches　a　stationary　one　its　sound　waves　bee　bunched　up　as　they　cramup　against　whatever　device　is　receiving　them　（your　ears；　say）；　just　as　you　would　expect　of　anything　that　is　beingpushed　from　behind　toward　an　immobile　object。　this　bunching　is　perceived　by　the　listener　as　a　kind　of　pinchedand　elevated　sound　（the　yee）。　as　the　sound　source　passes；　the　sound　waves　spread　out　and　lengthen；　causing　thepitch　to　drop　abruptly　（the　yummm）。

adonis”　in　the　words　of　another　admirer。　according　to　his　own　accounts；　he　also　managed　tofit　into　his　life　more　or　less　constant　acts　of　valor—rescuing　drowning　swimmers；　leadingfrightened　men　to　safety　across　the　battlefields　of　france；　embarrassing　world…championboxers　with　knockdown　punches　in　exhibition　bouts。　it　all　seemed　too　good　to　be　true。　it　was。

for　all　his　gifts；　hubble　was　also　an　inveterate　liar。

this　was　more　than　a　little　odd；　for　hubble’s　life　was　filled　from　an　early　age　with　a　levelof　distinction　that　was　at　times　almost　ludicrously　golden。　at　a　single　high　school　track　meetin　1906；　he　won　the　pole　vault；　shot　put；　discus；　hammer　throw；　standing　high　jump；　andrunning　high　jump；　and　was　on　the　winning　mile…relay　team—that　is　seven　first　places　in　onemeet—and　came　in　third　in　the　broad　jump。　in　the　same　year；　he　set　a　state　record　for　the　highjump　in　illinois。

as　a　scholar　he　was　equally　proficient；　and　had　no　trouble　gaining　admission　to　studyphysics　and　astronomy　at　the　university　of　chicago　（where；　coincidentally；　the　head　of　thedepartment　was　now　albert　michelson）。　there　he　was　selected　to　be　one　of　the　first　rhodesscholars　at　oxford。　three　years　of　english　life　evidently　turned　his　head；　for　he　returned　towheaton　in　1913　wearing　an　inverness　cape；　smoking　a　pipe；　and　talking　with　a　peculiarlyorotund　accent—not　quite　british　but　not　quite　not—that　would　remain　with　him　for　life。

though　he　later　claimed　to　have　passed　most　of　the　second　decade　of　the　century　practicinglaw　in　kentucky；　in　fact　he　worked　as　a　high　school　teacher　and　basketball　coach　in　newalbany；　indiana；　before　belatedly　attaining　his　doctorate　and　passing　briefly　through　thearmy。　（he　arrived　in　france　one　month　before　the　armistice　and　almost　certainly　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’s　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—the　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—howfar　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’t　tell　us　how　far　away　they　are　to　begin　with。　for　that　you　need　what　are　known　as“standard　candles”—stars　whose　brightness　can　be　reliably　calculated　and　used　asbenchmarks　to　measure　the　brightness　（and　hence　relative　distance）　of　other　stars。

hubble’s　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—hence　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—or　indeed　prettymuch　anywhere—in　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’s　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—a　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　“main　sequence　phase；”　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’s　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　“standard　candles”—a　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’s　cosmic　yardstick　with　vesto　slipher’s　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’t　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—vastly　vaster—thananyone　had　ever　supposed。　in　1924　he　produced　a　landmark　paper；　“cepheids　in　spiralnebulae”　（nebulae；from　the　latin　for　“clouds；”　was　his　word　for　galaxies）；　showing　that　theuniverse　consisted　not　just　of　the　milky　way　but　of　lots　of　independent　galaxies—“islanduniverses”—many　of