万物简史英文版_比尔·布莱森-第7章

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tention　to　a　question　that　had　long　troubled　astronomers：　the　appearance　in　thesky　of　occasional　unexplained　points　of　light；　new　stars。　improbably　he　wondered　if　theneutron鈥攖he　subatomic　particle　that　had　just　been　discovered　in　england　by　jameschadwick；　and　was　thus　both　novel　and　rather　fashionable鈥攎ight　be　at　the　heart　of　things。　itoccurred　to　him　that　if　a　star　collapsed　to　the　sort　of　densities　found　in　the　core　of　atoms；　theresult　would　be　an　unimaginably　pacted　core。　atoms　would　literally　be　crushed　together；their　electrons　forced　into　the　nucleus；　forming　neutrons。　you　would　have　a　neutron　star。

imagine　a　million　really　weighty　cannonballs　squeezed　down　to　the　size　of　a　marble　and鈥攚ell；　you鈥檙e　still　not　even　close。　the　core　of　a　neutron　star　is　so　dense　that　a　single　spoonfulof　matter　from　it　would　weigh　200　billion　pounds。　a　spoonful！　but　there　was　more。　zwickyrealized　that　after　the　collapse　of　such　a　star　there　would　be　a　huge　amount　of　energy　leftover鈥攅nough　to　make　the　biggest　bang　in　the　universe。　he　called　these　resultant　explosionssupernovae。　they　would　be鈥攖hey　are鈥攖he　biggest　events　in　creation。

on　january　15；　1934；　the　journal　physical　review　published　a　very　concise　abstract　of　apresentation　that　had　been　conducted　by　zwicky　and　baade　the　previous　month　at　stanforduniversity。　despite　its　extreme　brevity鈥攐ne　paragraph　of　twenty…four　lines鈥攖he　abstractcontained　an　enormous　amount　of　new　science：　it　provided　the　first　reference　to　supernovaeand　to　neutron　stars；　convincingly　explained　their　method　of　formation；　correctly　calculatedthe　scale　of　their　explosiveness；　and；　as　a　kind　of　concluding　bonus；　connected　supernovaexplosions　to　the　production　of　a　mysterious　new　phenomenon　called　cosmic　rays；　which　hadrecently　been　found　swarming　through　the　universe。　these　ideas　were　revolutionary　to　say　theleast。　neutron　stars　wouldn鈥檛　be　confirmed　for　thirty…four　years。　the　cosmic　rays　notion；though　considered　plausible；　hasn鈥檛　been　verified　yet。　altogether；　the　abstract　was；　in　thewords　of　caltech　astrophysicist　kip　s。　thorne；　鈥渙ne　of　the　most　prescient　documents　in　thehistory　of　physics　and　astronomy。鈥�

interestingly；　zwicky　had　almost　no　understanding　of　why　any　of　this　would　happen。

according　to　thorne；　鈥渉e　did　not　understand　the　laws　of　physics　well　enough　to　be　able　tosubstantiate　his　ideas。鈥潯�zwicky鈥檚　talent　was　for　big　ideas。　others鈥攂aade　mostly鈥攚ere　leftto　do　the　mathematical　sweeping　up。

zwicky　also　was　the　first　to　recognize　that　there　wasn鈥檛　nearly　enough　visible　mass　in　theuniverse　to　hold　galaxies　together　and　that　there　must　be　some　other　gravitational　influence鈥攚hat　we　now　call　dark　matter。　one　thing　he　failed　to　see　was　that　if　a　neutron　star　shrankenough　it　would　bee　so　dense　that　even　light　couldn鈥檛　escape　its　immense　gravitationalpull。　you　would　have　a　black　hole。　unfortunately；　zwicky　was　held　in　such　disdain　by　mostof　his　colleagues　that　his　ideas　attracted　almost　no　notice。　when；　five　years　later；　the　greatrobert　oppenheimer　turned　his　attention　to　neutron　stars　in　a　landmark　paper；　he　made　not　asingle　reference　to　any　of　zwicky鈥檚　work　even　though　zwicky　had　been　working　for　years　onthe　same　problem　in　an　office　just　down　the　hall。　zwicky鈥檚　deductions　concerning　dark　matterwouldn鈥檛　attract　serious　attention　for　nearly　four　decades。　we　can　only　assume　that　he　did　alot　of　pushups　in　this　period。

surprisingly　little　of　the　universe　is　visible　to　us　when　we　incline　our　heads　to　the　sky。　onlyabout　6；000　stars　are　visible　to　the　naked　eye　from　earth；　and　only　about　2；000　can　be　seenfrom　any　one　spot。　with　binoculars　the　number　of　stars　you　can　see　from　a　single　locationrises　to　about　50；000；　and　with　a　small　two…inch　telescope　it　leaps　to　300；000。　with　a　sixteen…inch　telescope；　such　as　evans　uses；　you　begin　to　count　not　in　stars　but　in　galaxies。　from　hisdeck；　evans　supposes　he　can　see　between　50；000　and　100；000　galaxies；　each　containing　tensof　billions　of　stars。　these　are　of　course　respectable　numbers；　but　even　with　so　much　to　take　in；supernovae　are　extremely　rare。　a　star　can　burn　for　billions　of　years；　but　it　dies　just　once　andquickly；　and　only　a　few　dying　stars　explode。　most　expire　quietly；　like　a　campfire　at　dawn。　in　atypical　galaxy；　consisting　of　a　hundred　billion　stars；　a　supernova　will　occur　on　average　onceevery　two　or　three　hundred　years。　finding　a　supernova　therefore　was　a　little　bit　like　standingon　the　observation　platform　of　the　empire　state　building　with　a　telescope　and　searchingwindows　around　manhattan　in　the　hope　of　finding；　let　us　say；　someone　lighting　a　twenty…first…birthday　cake。

so　when　a　hopeful　and　softspoken　minister　got　in　touch　to　ask　if　they　had　any　usable　fieldcharts　for　hunting　supernovae；　the　astronomical　munity　thought　he　was　out　of　his　mind。

at　the　time　evans　had　a　ten…inch　telescope鈥攁　very　respectable　size　for　amateur　stargazingbut　hardly　the　sort　of　thing　with　which　to　do　serious　cosmology鈥攁nd　he　was　proposing　tofind　one　of　the　universe鈥檚　rarer　phenomena。　in　the　whole　of　astronomical　history　before　evansstarted　looking　in　1980；　fewer　than　sixty　supernovae　had　been　found。　（at　the　time　i　visitedhim；　in　august　of　2001；　he　had　just　recorded　his　thirty…fourth　visual　discovery；　a　thirty…fifthfollowed　three　months　later　and　a　thirty…sixth　in　early　2003。）evans；　however；　had　certain　advantages。　most　observers；　like　most　people　generally；　are　inthe　northern　hemisphere；　so　he　had　a　lot　of　sky　largely　to　himself；　especially　at　first。　he　alsohad　speed　and　his　uncanny　memory。　large　telescopes　are　cumbersome　things；　and　much　oftheir　operational　time　is　consumed　with　being　maneuvered　into　position。　evans　could　swinghis　little　sixteen…inch　telescope　around　like　a　tail　gunner　in　a　dogfight；　spending　no　more　thana　couple　of　seconds　on　any　particular　point　in　the　sky。　in　consequence；　he　could　observeperhaps　four　hundred　galaxies　in　an　evening　while　a　large　professional　telescope　would　belucky　to　do　fifty　or　sixty。

looking　for　supernovae　is　mostly　a　matter　of　not　finding　them。　from　1980　to　1996　heaveraged　two　discoveries　a　year鈥攏ot　a　huge　payoff　for　hundreds　of　nights　of　peering　andpeering。　once　he　found　three　in　fifteen　days；　but　another　time　he　went　three　years　withoutfinding　any　at　all。

鈥渢here　is　actually　a　certain　value　in　not　finding　anything；鈥潯�he　said。　鈥渋t　helps　cosmologists　towork　out　the　rate　at　which　galaxies　are　evolving。　it鈥檚　one　of　those　rare　areas　where　theabsence　of　evidenceis　evidence。鈥�

on　a　table　beside　the　telescope　were　stacks　of　photos　and　papers　relevant　to　his　pursuits；and　he　showed　me　some　of　them　now。　if　you　have　ever　looked　through　popular　astronomicalpublications；　and　at　some　time　you　must　have；　you　will　know　that　they　are　generally　full　ofrichly　luminous　color　photos　of　distant　nebulae　and　the　like鈥攆airy…lit　clouds　of　celestial　lightof　the　most　delicate　and　moving　splendor。　evans鈥檚　working　images　are　nothing　like　that。　theyare　just　blurry　black…and…white　photos　with　little　points　of　haloed　brightness。　one　he　showedme　depicted　a　swarm　of　stars　with　a　trifling　flare　that　i　had　to　put　close　to　my　face　to　see。

this；　evans　told　me；　was　a　star　in　a　constellation　called　fornax　from　a　galaxy　known　toastronomy　as　ngc1365。　（ngc　stands　for　new　general　catalogue；　where　these　things　arerecorded。　once　it　was　a　heavy　book　on　someone鈥檚　desk　in　dublin；　today；　needless　to　say；　it鈥檚a　database。）　for　sixty　million　silent　years；　the　light　from　the　star鈥檚　spectacular　demise　traveledunceasingly　through　space　until　one　night　in　august　of　2001　it　arrived　at　earth　in　the　form　ofa　puff　of　radiance；　the　tiniest　brightening；　in　the　night　sky。　it　was　of　course　robert　evans　onhis　eucalypt…scented　hillside　who　spotted　it。

鈥渢here鈥檚　something　satisfying；　i　think；鈥潯�evans　said；　鈥渁bout　the　idea　of　light　traveling　formillions　of　years　through　space　and　just　at　the　right　moment　as　it　reaches　earth　someonelooks　at　the　right　bit　of　sky　and　sees　it。　it　just　seems　right　that　an　event　of　that　magnitudeshould　be　witnessed。鈥�

supernovae　do　much　more　than　simply　impart　a　sense　of　wonder。　they　e　in　severaltypes　（one　of　them　discovered　by　evans）　and　of　these　one　in　particular；　known　as　a　iasupernova；　is　important　to　astronomy　because　it　always　explodes　in　the　same　way；　with　thesame　critical　mass。　for　this　reason　it　can　be　used　as　a　standard　candle　to　measure　theexpansion　rate　of　the　universe。

in　1987　saul　perlmutter　at　the　lawrence　berkeley　lab　in　california；　needing　more　iasupernovae　than　visual　sightings　were　providing；　set　out　to　find　a　more　systematic　method　ofsearching　for　them。　perlmutter　devised　a　nifty　system　using　sophisticated　puters　andcharge…coupled　devices鈥攊n　essence；　really　good　digital　cameras。　it　automated　supernovahunting。　telescopes　could　now　take　thousands　of　pictures　and　let　a　puter　detect　thetelltale　bright　spots　that　marked　a　supernova　explosion。　in　five　years；　with　the　new　technique；perlmutter　and　his　colleagues　at　berkeley　found　forty…two　supernovae。　now　even　amateursare　finding　supernovae　with　charge…coupled　devices。　鈥渨ith　ccds　you　can　aim　a　telescope　atthe　sky　and　go　watch　television；鈥潯�evans　said　with　a　touch　of　dismay。　鈥渋t　took　all　the　romanceout　of　it。鈥�

i　asked　him　if　he　was　tempted　to　adopt　the　new　technology。　鈥渙h；　no；鈥潯�he　said；　鈥渋　enjoy　myway　too　much。　besides鈥濃�攈e　gave　a　nod　at　the　photo　of　his　latest　supernova　and　smiled鈥斺�渋can　still　beat　them　sometimes。鈥�

the　question　that　naturally　occurs　is　鈥渨hat　would　it　be　like　if　a　star　exploded　nearby？鈥潯�ournearest　stellar　neighbor；　as　we　have　seen；　is　alpha　centauri；　4。3　light…years　away。　i　hadimagined　that　if　there　were　an　explosion　there　we　would　have　4。3　years　to　watch　the　light　ofthis　magnificent　event　spreading　across　the　sky；　as　if　tipped　from　a　giant　can。　what　would　itbe　like　if　we　had　four　years　and　four　months　to　watch　an　inescapable　doom　advancing　towardus；　knowing　that　when　it　finally　arrived　it　would　blow　the　skin　right　off　our　bones？　wouldpeople　still　go　to　work？　would　farmers　plant　crops？　would　anyone　deliver　them　to　the　stores？

weeks　later；　back　in　the　town　in　new　hampshire　where　i　live；　i　put　these　questions　to　johnthorstensen；　an　astronomer　at　dartmouth　college。　鈥渙h　no；鈥潯�he　said；　laughing。　鈥渢he　news　ofsuch　an　event　travels　out　at　the　speed　of　light；　but　so　does　the　destructiveness；　so　you鈥檇　learnabout　it　and　die　from　it　in　the　same　instant。　but　don鈥檛　worry　because　it鈥檚　not　going　to　happen。鈥�

for　the　blast　of　a　supernova　explosion　to　kill　you；　he　explained；　you　would　have　to　be鈥渞idiculously　close鈥濃�攑robably　within　ten　light…years　or　so。　鈥渢he　danger　would　be　varioustypes　of　radiation鈥攃osmic　rays　and　so　on。鈥潯�these　would　produce　fabulous　auroras；shimmering　curtains　of　spooky　light　that　would　fill　the　whole　sky。　this　would　not　be　a　goodthing。　anything　potent　enough　to　put　on　such　a　show　could　well　blow　away　themagnetosphere；　the　magnetic　zone　high　above　the　earth　that　normally　protects　us　fromultraviolet　rays　and　other　cosmic　assaults。　without　the　magnetosphere　anyone　unfortunateenough　to　step　into　sunlight　would　pretty　quickly　take　on　the　appearance　of；　let　us　say；　anovercooked　pizza。

the　reason　we　can　be　reasonably　confident　that　such　an　event　won鈥檛　happen　i