万物简史英文版_比尔·布莱森-第8章

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anovercooked　pizza。

the　reason　we　can　be　reasonably　confident　that　such　an　event　won鈥檛　happen　in　our　cornerof　the　galaxy；　thorstensen　said；　is　that　it　takes　a　particular　kind　of　star　to　make　a　supernova　inthe　first　place。　a　candidate　star　must　be　ten　to　twenty　times　as　massive　as　our　own　sun　and鈥渨e　don鈥檛　have　anything　of　the　requisite　size　that鈥檚　that　close。　the　universe　is　a　mercifully　bigplace。鈥潯�the　nearest　likely　candidate　he　added；　is　betelgeuse；　whose　various　sputterings　havefor　years　suggested　that　something　interestingly　unstable　is　going　on　there。　but　betelgeuse　isfifty　thousand　light…years　away。

only　half　a　dozen　times　in　recorded　history　have　supernovae　been　close　enough　to　bevisible　to　the　naked　eye。　one　was　a　blast　in　1054　that　created　the　crab　nebula。　another；　in1604；　made　a　star　bright　enough　to　be　seen　during　the　day　for　over　three　weeks。　the　mostrecent　was　in　1987；　when　a　supernova　flared　in　a　zone　of　the　cosmos　known　as　the　largemagellanic　cloud；　but　that　was　only　barely　visible　and　only　in　the　southern　hemisphere鈥攁ndit　was　a　fortably　safe　169；000　light…years　away。

supernovae　are　significant　to　us　in　one　other　decidedly　central　way。　without　them　wewouldn鈥檛　be　here。　you　will　recall　the　cosmological　conundrum　with　which　we　ended　the　firstchapter鈥攖hat　the　big　bang　created　lots　of　light　gases　but　no　heavy　elements。　those　camelater；　but　for　a　very　long　time　nobody　could　figure　out　　how　they　came　later。　the　problem　wasthat　you　needed　something　really　hot鈥攈otter　even　than　the　middle　of　the　hottest　stars鈥攖oforge　carbon　and　iron　and　the　other　elements　without　which　we　would　be　distressinglyimmaterial。　supernovae　provided　the　explanation；　and　it　was　an　english　cosmologist　almostas　singular　in　manner　as　fritz　zwicky　who　figured　it　out。

he　was　a　yorkshireman　named　fred　hoyle。　hoyle；　who　died　in　2001；　was　described　in　anobituary　in　nature　as　a　鈥渃osmologist　and　controversialist鈥潯�and　both　of　those　he　most　certainlywas。　he　was；　according　to　nature　鈥檚　obituary；　鈥渆mbroiled　in　controversy　for　most　of　his　life鈥�

and　鈥減ut　his　name　to　much　rubbish。鈥潯�he　claimed；　for　instance；　and　without　evidence；　that　thenatural　history　museum鈥檚　treasured　fossil　of　an　archaeopteryx　was　a　forgery　along　the　linesof　the　piltdown　hoax；　causing　much　exasperation　to　the　museum鈥檚　paleontologists；　who　had　tospend　days　fielding　phone　calls　from　journalists　from　all　over　the　world。　he　also　believed　thatearth　was　not　only　seeded　by　life　from　space　but　also　by　many　of　its　diseases；　such　asinfluenza　and　bubonic　plague；　and　suggested　at　one　point　that　humans　evolved　projectingnoses　with　the　nostrils　underneath　as　a　way　of　keeping　cosmic　pathogens　from　falling　intothem。

it　was　he　who　coined　the　term　鈥渂ig　bang；鈥潯�in　a　moment　of　facetiousness；　for　a　radiobroadcast　in　1952。　he　pointed　out　that　nothing　in　our　understanding　of　physics　could　accountfor　why　everything；　gathered　to　a　point；　would　suddenly　and　dramatically　begin　to　expand。

hoyle　favored　a　steady…state　theory　in　which　the　universe　was　constantly　expanding　andcontinually　creating　new　matter　as　it　went。　hoyle　also　realized　that　if　stars　imploded　theywould　liberate　huge　amounts　of　heat鈥�100　million　degrees　or　more；　enough　to　begin　togenerate　the　heavier　elements　in　a　process　known　as　nucleosynthesis。　in　1957；　working　withothers；　hoyle　showed　how　the　heavier　elements　were　formed　in　supernova　explosions。　forthis　work；　w。　a。　fowler；　one　of　his　collaborators；　received　a　nobel　prize。　hoyle；　shamefully；did　not。

according　to　hoyle鈥檚　theory；　an　exploding　star　would　generate　enough　heat　to　create　all　thenew　elements　and　spray　them　into　the　cosmos　where　they　would　form　gaseous　clouds鈥攖heinterstellar　medium　as　it　is　known鈥攖hat　could　eventually　coalesce　into　new　solar　systems。

with　the　new　theories　it　became　possible　at　last　to　construct　plausible　scenarios　for　how　wegot　here。　what　we　now　think　we　know　is　this：

about　4。6　billion　years　ago；　a　great　swirl　of　gas　and　dust　some　15　billion　miles　acrossaccumulated　in　space　where　we　are　now　and　began　to　aggregate。　virtually　all　of　it鈥�99。9percent　of　the　mass　of　the　solar　system鈥攚ent　to　make　the　sun。　out　of　the　floating　materialthat　was　left　over；　two　microscopic　grains　floated　close　enough　together　to　be　joined　byelectrostatic　forces。　this　was　the　moment　of　conception　for　our　planet。　all　over　the　inchoatesolar　system；　the　same　was　happening。　colliding　dust　grains　formed　larger　and　larger　clumps。

eventually　the　clumps　grew　large　enough　to　be　called　planetesimals。　as　these　endlesslybumped　and　collided；　they　fractured　or　split　or　rebined　in　endless　random　permutations；but　in　every　encounter　there　was　a　winner；　and　some　of　the　winners　grew　big　enough　todominate　the　orbit　around　which　they　traveled。

it　all　happened　remarkably　quickly。　to　grow　from　a　tiny　cluster　of　grains　to　a　baby　planetsome　hundreds　of　miles　across　is　thought　to　have　taken　only　a　few　tens　of　thousands　of　years。

in　just　200　million　years；　possibly　less；　the　earth　was　essentially　formed；　though　still　moltenand　subject　to　constant　bombardment　from　all　the　debris　that　remained　floating　about。

at　this　point；　about　4。5　billion　years　ago；　an　object　the　size　of　mars　crashed　into　earth；blowing　out　enough　material　to　form　a　panion　sphere；　the　moon。　within　weeks；　it　isthought；　the　flung　material　had　reassembled　itself　into　a　single　clump；　and　within　a　year　it　hadformed　into　the　spherical　rock　that　panions　us　yet。　most　of　the　lunar　material；　it　isthought；　came　from　the　earth鈥檚　crust；　not　its　core；　which　is　why　the　moon　has　so　little　ironwhile　we　have　a　lot。　the　theory；　incidentally；　is　almost　always　presented　as　a　recent　one；　butin　fact　it　was　first　proposed　in　the　1940s　by　reginald　daly　of　harvard。　the　only　recent　thingabout　it　is　people　paying　any　attention　to　it。

when　earth　was　only　about　a　third　of　its　eventual　size；　it　was　probably　already　beginning　toform　an　atmosphere；　mostly　of　carbon　dioxide；　nitrogen；　methane；　and　sulfur。　hardly　the　sortof　stuff　that　we　would　associate　with　life；　and　yet　from　this　noxious　stew　life　formed。　carbondioxide　is　a　powerful　greenhouse　gas。　this　was　a　good　thing　because　the　sun　wassignificantly　dimmer　back　then。　had　we　not　had　the　benefit　of　a　greenhouse　effect；　the　earthmight　well　have　frozen　over　permanently；　and　life　might　never　have　gotten　a　toehold。　butsomehow　life　did。

for　the　next　500　million　years　the　young　earth　continued　to　be　pelted　relentlessly　byets；　meteorites；　and　other　galactic　debris；　which　brought　water　to　fill　the　oceans　and　theponents　necessary　for　the　successful　formation　of　life。　it　was　a　singularly　hostileenvironment　and　yet　somehow　life　got　going。　some　tiny　bag　of　chemicals　twitched　andbecame　animate。　we　were　on　our　way。

four　billion　years　later　people　began　to　wonder　how　it　had　all　happened。　and　it　is　there　thatour　story　next　takes　us。

part　　ii　the　size　of　the　earthnature　and　nature鈥檚　laws　lay　hid　innight；god　said；　let　newton　be！　and　allwas　light。

…alexander　pope





4　　　　THE　MEASURE　OF　THINGS


if　you　had　to　select　the　least　convivial　scientific　field　trip　of　all　time；　you　could　certainlydo　worse　than　the　french　royal　academy　of　sciences鈥櫋�peruvian　expedition　of　1735。　led　by　ahydrologist　named　pierre　bouguer　and　a　soldier…mathematician　named　charles　marie　de　lacondamine；　it　was　a　party　of　scientists　and　adventurers　who　traveled　to　peru　with　the　purposeof　triangulating　distances　through　the　andes。

at　the　time　people　had　lately　bee　infected　with　a　powerful　desire　to　understand　theearth鈥攖o　determine　how　old　it　was；　and　how　massive；　where　it　hung　in　space；　and　how　it　hade　to　be。　the　french　party鈥檚　goal　was　to　help　settle　the　question　of　the　circumference　ofthe　planet　by　measuring　the　length　of　one　degree　of　meridian　（or　1/360　of　the　distance　aroundthe　planet）　along　a　line　reaching　from　yarouqui；　near　quito；　to　just　beyond　cuenca　in　what　isnow　ecuador；　a　distance　of　about　two　hundred　miles。

1almost　at　once　things　began　to　go　wrong；　sometimes　spectacularly　so。　in　quito；　the　visitorssomehow　provoked　the　locals　and　were　chased　out　of　town　by　a　mob　armed　with　stones。　soonafter；　the　expedition鈥檚　doctor　was　murdered　in　a　misunderstanding　over　a　woman。　thebotanist　became　deranged。　others　died　of　fevers　and　falls。　the　third　most　senior　member　ofthe　party；　a　man　named　pierre　godin；　ran　off　with　a　thirteen…year…old　girl　and　could　not　beinduced　to　return。

at　one　point　the　group　had　to　suspend　work　for　eight　months　while　la　condamine　rode　off　tolima　to　sort　out　a　problem　with　their　permits。　eventually　he　and　bouguer　stopped　speakingand　refused　to　work　together。　everywhere　the　dwindling　party　went　it　was　met　with　thedeepest　suspicions　from　officials　who　found　it　difficult　to　believe　that　a　group　of　frenchscientists　would　travel　halfway　around　the　world　to　measure　the　world。　that　made　no　sense　atall。　two　and　a　half　centuries　later　it　still　seems　a　reasonable　question。　why　didn鈥檛　the　frenchmake　their　measurements　in　france　and　save　themselves　all　the　bother　and　disfort　of　theirandean　adventure？

the　answer　lies　partly　with　the　fact　that　eighteenth…century　scientists；　the　french　in　particular；seldom　did　things　simply　if　an　absurdly　demanding　alternative　was　available；　and　partly　witha　practical　problem　that　had　first　arisen　with　the　english　astronomer　edmond　halley　manyyears　before鈥攍ong　before　bouguer　and　la　condamine　dreamed　of　going　to　south　america；much　less　had　a　reason　for　doing　so。

*　triangulation；　their　chosen　method；　was　a　popular　technique　based　on　the　geometric　fact　that　if　you　know　thelength　of　one　side　of　a　triangle　and　the　angles　of　two　corners；　you　can　work　out　all　its　other　dimensions　withoutleaving　your　chair。　suppose；　by　way　of　example；　that　you　and　i　decided　we　wished　to　know　how　far　it　is　to　themoon。　using　triangulation；　the　first　thing　we　must　do　is　put　some　distance　between　us；　so　lets　say　for　argumentthat　you　stay　in　paris　and　i　go　to　moscow　and　we　both　look　at　the　moon　at　the　same　time。　now　if　you　imagine　aline　connecting　the　three　principals　of　this　exercise…that　is；　you　and　i　and　the　moon…it　forms　a　triangle。　measurethe　length　of　the　baseline　between　you　and　me　and　the　angles　of　our　two　corners　and　the　rest　can　be　simplycalculated。　（because　the　interior　angles　of　a　triangle　always　add　up　to　180　degrees；　if　you　know　the　sum　of　twoof　the　angles　you　can　instantly　calculate　the　third；　and　knowing　the　precise　shape　of　a　triangle　and　the　length　ofone　side　tells　you　the　lengths　of　the　other　sides。）　this　was　in　fact　the　method　use　by　a　greek　astronomer；hipparchus　of　nicaea；　in　150　b。c。　to　work　out　the　moons　distance　from　earth。　at　ground　level；　the　principles　oftriangulation　are　the　same；　except　that　the　triangles　dont　reach　into　space　but　rather　are　laid　side　to　side　on　amap。　in　measuring　a　degree　of　meridian；　the　surveyors　would　create　a　sort　of　chain　of　triangles　marching　acrossthe　landscape。

halley　was　an　exceptional　figure。　in　the　course　of　a　long　and　productive　career；　he　was　asea　captain；　a　cartographer；　a　professor　of　geometry　at　the　university　of　oxford；　deputycontroller　of　the　royal　mint；　astronomer　royal；　and　inventor　of　the　deep…sea　diving　bell。　hewrote　authoritatively　on　magnetism；　tides；　and　the　motions　of　the　planets；　and　fo