万物简史英文版_比尔·布莱森-第52章

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鈥渉e　was　just　a　great　guy；鈥潯�witzke　replied　without　hesitation。　鈥渋f　it　hadn鈥檛　been　for　him；　thewhole　thing　would　never　have　gotten　off　the　ground。　even　with　his　support；　it　took　two　yearsto　get　it　up　and　running。　drilling鈥檚　an　expensive　business鈥攁bout　thirty…five　dollars　a　footback　then；　more　now；　and　we　needed　to　go　down　three　thousand　feet。鈥�

鈥渟ometimes　more　than　that；鈥潯�anderson　added。

鈥渟ometimes　more　than　that；鈥潯�witzke　agreed。　鈥渁nd　at　several　locations。　so　you鈥檙e　talking　alot　of　money。　certainly　more　than　our　budget　would　allow。鈥�

so　　a　　collaboration　　was　　formed　　between　the　iowa　geological　survey　and　the　u。s。

geological　survey。

鈥渁t　least　we　thought　it　was　a　collaboration；鈥潯�said　anderson；　producing　a　small　painedsmile。

鈥渋t　was　a　real　learning　curve　for　us；鈥潯�witzke　went　on。　鈥渢here　was　actually　quite　a　lot　of　badscience　going　on　throughout　the　period鈥攑eople　rushing　in　with　results　that　didn鈥檛　alwaysstand　up　to　scrutiny。鈥潯�one　of　those　moments　came　at　the　annual　meeting　of　the　americangeophysical　union　in　1985；　when　glenn　izett　and　c。　l。　pillmore　of　the　u。s。　geologicalsurvey　announced　that　the　manson　crater　was　of　the　right　age　to　have　been　involved　with　thedinosaurs鈥櫋�extinction。　the　declaration　attracted　a　good　deal　of　press　attention　but　wasunfortunately　premature。　a　more　careful　examination　of　the　data　revealed　that　manson　wasnot　only　too　small；　but　also　nine　million　years　too　early。

the　first　anderson　or　witzke　learned　of　this　setback　to　their　careers　was　when　they　arrivedat　a　conference　in　south　dakota　and　found　people　ing　up　to　them　with　sympathetic　looksand　saying：　鈥渨e　hear　you　lost　your　crater。鈥潯�it　was　the　first　they　knew　that　izett　and　the　otherusgs　scientists　had　just　announced　refined　figures　revealing　that　manson　couldn鈥檛　after　allhave　been　the　extinction　crater。

鈥渋t　was　pretty　stunning；鈥潯�recalls　anderson。　鈥渋　mean；　we　had　this　thing　that　was　reallyimportant　and　then　suddenly　we　didn鈥檛　have　it　anymore。　but　even　worse　was　the　realizationthat　the　people　we　thought　we鈥檇　been　collaborating　with　hadn鈥檛　bothered　to　share　with　us　theirnew　findings。鈥�

鈥渨hy　not？鈥�

he　shrugged。　鈥渨ho　knows？　anyway；　it　was　a　pretty　good　insight　into　how　unattractivescience　can　get　when　you鈥檙e　playing　at　a　certain　level。鈥�

the　search　moved　elsewhere。　by　chance　in　1990　one　of　the　searchers；　alan　hildebrand　ofthe　university　of　arizona；　met　a　reporter　from　the　houston　chronicle　who　happened　to　knowabout　a　large；　unexplained　ring　formation；　120　miles　wide　and　30　miles　deep；　under　mexico鈥檚yucat谩n　peninsula　at　chicxulub；　near　the　city　of　progreso；　about　600　miles　due　south　of　neworleans。　the　formation　had　been　found　by　pemex；　the　mexican　oil　pany；　in　1952鈥攖heyear；　coincidentally；　that　gene　shoemaker　first　visited　meteor　crater　in　arizona鈥攂ut　thepany鈥檚　geologists　had　concluded　that　it　was　volcanic；　in　line　with　the　thinking　of　the　day。

hildebrand　traveled　to　the　site　and　decided　fairly　swiftly　that　they　had　their　crater。　by　early1991　it　had　been　established　to　nearly　everyone鈥檚　satisfaction　that　chicxulub　was　the　impactsite。

still；　many　people　didn鈥檛　quite　grasp　what　an　impact　could　do。　as　stephen　jay　gouldrecalled　in　one　of　his　essays：　鈥渋　remember　harboring　some　strong　initial　doubts　about　theefficacy　of　such　an　event　。　。　。　＇w＇hy　should　an　object　only　six　miles　across　wreak　such　havocupon　a　planet　with　a　diameter　of　eight　thousand　miles？鈥�

conveniently　a　natural　test　of　the　theory　arose　when　the　shoemakers　and　levy　discoveredet　shoemaker…levy　9；　which　they　soon　realized　was　headed　for　jupiter。　for　the　first　time；humans　would　be　able　to　witness　a　cosmic　collision鈥攁nd　witness　it　very　well　thanks　to　thenew　hubble　space　telescope。　most　astronomers；　according　to　curtis　peebles；　expected　little；particularly　as　the　et　was　not　a　coherent　sphere　but　a　string　of　twenty…one　fragments。　鈥渕ysense；鈥潯�wrote　one；　鈥渋s　that　jupiter　will　swallow　these　ets　up　without　so　much　as　a　burp。鈥�

one　week　before　the　impact；　nature　ran　an　article；　鈥渢he　big　fizzle　is　ing；鈥潯�predictingthat　the　impact　would　constitute　nothing　more　than　a　meteor　shower。

the　impacts　began　on　july　16；　1994；　went　on　for　a　week　and　were　bigger　by　far　thananyone鈥攚ith　the　possible　exception　of　gene　shoemaker鈥攅xpected。　one　fragment；　knownas　nucleus　g；　struck　with　the　force　of　about　six　million　megatons鈥攕eventy…five　times　morethan　all　the　nuclear　weaponry　in　existence。　nucleus　g　was　only　about　the　size　of　a　smallmountain；　but　it　created　wounds　in　the　jovian　surface　the　size　of　earth。　it　was　the　final　blowfor　critics　of　the　alvarez　theory。

luis　alvarez　never　knew　of　the　discovery　of　the　chicxulub　crater　or　of　the　shoemaker…levy　et；　as　he　died　in　1988。　shoemaker　also　died　early。　on　the　third　anniversary　of　theshoemaker…levy　impact；　he　and　his　wife　were　in　the　australian　outback；　where　they　wentevery　year　to　search　for　impact　sites。　on　a　dirt　track　in　the　tanami　desert鈥攏ormally　one　ofthe　emptiest　places　on　earth鈥攖hey　came　over　a　slight　rise　just　as　another　vehicle　wasapproaching。　shoemaker　was　killed　instantly；　his　wife　injured。　part　of　his　ashes　were　sent　tothe　moon　aboard　the　lunar　prospector　spacecraft。　the　rest　were　scattered　around　meteorcrater。

anderson　and　witzke　no　longer　had　the　crater　that　killed　the　dinosaurs；　鈥渂ut　we　still　hadthe　largest　and　most　perfectly　preserved　impact　crater　in　the　mainland　united　states；鈥�

anderson　said。　（a　little　verbal　dexterity　is　required　to　keep　manson鈥檚　superlative　status。　othercraters　are　larger鈥攏otably；　chesapeake　bay；　which　was　recognized　as　an　impact　site　in1994鈥攂ut　they　are　either　offshore　or　deformed。）　鈥渃hicxulub　is　buried　under　two　to　threekilometers　of　limestone　and　mostly　offshore；　which　makes　it　difficult　to　study；鈥潯�andersonwent　on；　鈥渨hile　manson　is　really　quite　accessible。　it鈥檚　because　it　is　buried　that　it　is　actuallyparatively　pristine。鈥�

i　asked　them　how　much　warning　we　would　receive　if　a　similar　hunk　of　rock　was　ingtoward　us　today。

鈥渙h；　probably　none；鈥潯�said　anderson　breezily。　鈥渋t　wouldn鈥檛　be　visible　to　the　naked　eye　untilit　warmed　up；　and　that　wouldn鈥檛　happen　until　it　hit　the　atmosphere；　which　would　be　about　onesecond　before　it　hit　the　earth。　you鈥檙e　talking　about　something　moving　many　tens　of　timesfaster　than　the　fastest　bullet。　unless　it　had　been　seen　by　someone　with　a　telescope；　and　that鈥檚by　no　means　a　certainty；　it　would　take　us　pletely　by　surprise。鈥�

how　hard　an　impactor　hits　depends　on　a　lot　of　variables鈥攁ngle　of　entry；　velocity　andtrajectory；　whether　the　collision　is　head…on　or　from　the　side；　and　the　mass　and　density　of　theimpacting　object；　among　much　else鈥攏one　of　which　we　can　know　so　many　millions　of　yearsafter　the　fact。　but　what　scientists　can　do鈥攁nd　anderson　and　witzke　have　done鈥攊s　measurethe　impact　site　and　calculate　the　amount　of　energy　released。　from　that　they　can　work　outplausible　scenarios　of　what　it　must　have　been　like鈥攐r；　more　chillingly；　would　be　like　if　ithappened　now。

an　asteroid　or　et　traveling　at　cosmic　velocities　would　enter　the　earth鈥檚　atmosphere　atsuch　a　speed　that　the　air　beneath　it　couldn鈥檛　get　out　of　the　way　and　would　be　pressed；　as　ina　bicycle　pump。　as　anyone　who　has　used　such　a　pump　knows；　pressed　air　grows　swiftlyhot；　and　the　temperature　below　it　would　rise　to　some　60；000　kelvin；　or　ten　times　the　surfacetemperature　of　the　sun。　in　this　instant　of　its　arrival　in　our　atmosphere；　everything　in　themeteor鈥檚　path鈥攑eople；　houses；　factories；　cars鈥攚ould　crinkle　and　vanish　like　cellophane　in　aflame。

one　second　after　entering　the　atmosphere；　the　meteorite　would　slam　into　the　earth鈥檚surface；　where　the　people　of　manson　had　a　moment　before　been　going　about　their　business。

the　meteorite　itself　would　vaporize　instantly；　but　the　blast　would　blow　out　a　thousand　cubickilometers　of　rock；　earth；　and　superheated　gases。　every　living　thing　within　150　miles　thathadn鈥檛　been　killed　by　the　heat　of　entry　would　now　be　killed　by　the　blast。　radiating　outward　atalmost　the　speed　of　light　would　be　the　initial　shock　wave；　sweeping　everything　before　it。

for　those　outside　the　zone　of　immediate　devastation；　the　first　inkling　of　catastro