A Short History of Nearly Everything-第92章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


rpentier　told　the　story　of　how　in　1834　he　was　walking　along　a　countrylane　with　a　swiss　woodcutter　when　they　got　to　talking　about　the　rocks　along　the　roadside。　thewoodcutter　matter…of…factly　told　him　that　the　boulders　had　e　from　the　grimsel；　a　zone　ofgranite　some　distance　away。　“when　i　asked　him　how　he　thought　that　these　stones　had　reachedtheir　location；　he　answered　without　hesitation：　‘the　grimsel　glacier　transported　them　on　bothsides　of　the　valley；　because　that　glacier　extended　in　the　past　as　far　as　the　town　of　bern。’　”

charpentier　was　delighted。　he　had　e　to　such　a　view　himself；　but　when　he　raised　thenotion　at　scientific　gatherings；　it　was　dismissed。　one　of　charpentier’s　closest　friends　wasanother　swiss　naturalist；　louis　agassiz；　who　after　some　initial　skepticism　came　to　embrace；and　eventually　all　but　appropriate；　the　theory。

agassiz　had　studied　under　cuvier　in　paris　and　now　held　the　post　of　professor　of　naturalhistory　at　the　college　of　neuchatel　in　switzerland。　another　friend　of　agassiz’s；　a　botanistnamed　karl　schimper；　was　actually　the　first　to　coin　the　term　ice　age　（in　german　eiszeit　）；　in1837；　and　to　propose　that　there　was　good　evidence　to　show　that　ice　had　once　lain　heavilyacross　not　just　the　swiss　alps；　but　over　much　of　europe；　asia；　and　north　america。　it　was　aradical　notion。　he　lent　agassiz　his　notes—then　came　very　much　to　regret　it　as　agassizincreasingly　got　the　credit　for　what　schimper　felt；　with　some　legitimacy；　was　his　theory。

charpentier　likewise　ended　up　a　bitter　enemy　of　his　old　friend。　alexander　von　humboldt；　yetanother　friend；　may　have　had　agassiz　at　least　partly　in　mind　when　he　observed　that　there　arethree　stages　in　scientific　discovery：　first；　people　deny　that　it　is　true；　then　they　deny　that　it　isimportant；　finally　they　credit　the　wrong　person。

at　all　events；　agassiz　made　the　field　his　own。　in　his　quest　to　understand　the　dynamics　ofglaciation；　he　went　everywhere—deep　into　dangerous　crevasses　and　up　to　the　summits　of　thecraggiest　alpine　peaks；　often　apparently　unaware　that　he　and　his　team　were　the　first　to　climbthem。　nearly　everywhere　agassiz　encountered　an　unyielding　reluctance　to　accept　his　theories。

humboldt　urged　him　to　return　to　his　area　of　real　expertise；　fossil　fish；　and　give　up　this　madobsession　with　ice；　but　agassiz　was　a　man　possessed　by　an　idea。

agassiz’s　theory　found　even　less　support　in　britain；　where　most　naturalists　had　never　seena　glacier　and　often　couldn’t　grasp　the　crushing　forces　that　ice　in　bulk　exerts。　“could　scratchesand　polish　just　be　due　to　ice　？”　asked　roderick　murchison　in　a　mocking　tone　at　one　meeting；evidently　imagining　the　rocks　as　covered　in　a　kind　of　light　and　glassy　rime。　to　his　dying　day；he　expressed　the　frankest　incredulity　at　those　“ice…mad”　geologists　who　believed　that　glacierscould　account　for　so　much。　william　hopkins；　a　cambridge　professor　and　leading　member　ofthe　geological　society；　endorsed　this　view；　arguing　that　the　notion　that　ice　could　transportboulders　presented　“such　obvious　mechanical　absurdities”　as　to　make　it　unworthy　of　thesociety’s　attention。

undaunted；　agassiz　traveled　tirelessly　to　promote　his　theory。　in　1840　he　read　a　paper　to　ameeting　of　the　british　association　for　the　advancement　of　science　in　glasgow　at　which　hewas　openly　criticized　by　the　great　charles　lyell。　the　following　year　the　geological　society　ofedinburgh　passed　a　resolution　conceding　that　there　might　be　some　general　merit　in　the　theorybut　that　certainly　none　of　it　applied　to　scotland。

lyell　did　eventually　e　round。　his　moment　of　epiphany　came　when　he　realized　that　amoraine；　or　line　of　rocks；　near　his　family　estate　in　scotland；　which　he　had　passed　hundreds　oftimes；　could　only　be　understood　if　one　accepted　that　a　glacier　had　dropped　them　there。　buthaving　bee　converted；　lyell　then　lost　his　nerve　and　backed　off　from　public　support　of　theice　age　idea。　it　was　a　frustrating　time　for　agassiz。　his　marriage　was　breaking　up；　schimperwas　hotly　accusing　him　of　the　theft　of　his　ideas；　charpentier　wouldn’t　speak　to　him；　and　thegreatest　living　geologist　offered　support　of　only　the　most　tepid　and　vacillating　kind。

in　1846；　agassiz　traveled　to　america　to　give　a　series　of　lectures　and　there　at　last　found　theesteem　he　craved。　harvard　gave　him　a　professorship　and　built　him　a　first…rate　museum；　themuseum　of　parative　zoology。　doubtless　it　helped　that　he　had　settled　in　new　england；where　the　long　winters　encouraged　a　certain　sympathy　for　the　idea　of　interminable　periods　ofcold。　it　also　helped　that　six　years　after　his　arrival　the　first　scientific　expedition　to　greenlandreported　that　nearly　the　whole　of　that　semicontinent　was　covered　in　an　ice　sheet　just　like　theancient　one　imagined　in　agassiz’s　theory。　at　long　last；　his　ideas　began　to　find　a　realfollowing。　the　one　central　defect　of　agassiz’s　theory　was　that　his　ice　ages　had　no　cause。　butassistance　was　about　to　e　from　an　unlikely　quarter。

in　the　1860s；　journals　and　other　learned　publications　in　britain　began　to　receive　papers　onhydrostatics；　electricity；　and　other　scientific　subjects　from　a　james　croll　of　anderson’suniversity　in　glasgow。　one　of　the　papers；　on　how　variations　in　earth’s　orbit　might　haveprecipitated　ice　ages；　was　published　in　the　philosophical　magazine　in　1864　and　wasrecognized　at　once　as　a　work　of　the　highest　standard。　so　there　was　some　surprise；　and　perhapsjust　a　touch　of　embarrassment；　when　it　turned　out　that　croll　was　not　an　academic　at　theuniversity；　but　a　janitor。

born　in　1821；　croll　grew　up　poor；　and　his　formal　education　lasted　only　to　the　age　ofthirteen。　he　worked　at　a　variety　of　jobs—as　a　carpenter；　insurance　salesman；　keeper　of　atemperance　hotel—before　taking　a　position　as　a　janitor　at　anderson’s　（now　the　university　ofstrathclyde）　in　glasgow。　by　somehow　inducing　his　brother　to　do　much　of　his　work；　he　wasable　to　pass　many　quiet　evenings　in　the　university　library　teaching　himself　physics；mechanics；　astronomy；　hydrostatics；　and　the　other　fashionable　sciences　of　the　day；　andgradually　began　to　produce　a　string　of　papers；　with　a　particular　emphasis　on　the　motions　ofearth　and　their　effect　on　climate。

croll　was　the　first　to　suggest　that　cyclical　changes　in　the　shape　of　earth’s　orbit；　fromelliptical　（which　is　to　say　slightly　oval）　to　nearly　circular　to　elliptical　again；　might　explain　theonset　and　retreat　of　ice　ages。　no　one　had　ever　thought　before　to　consider　an　astronomicalexplanation　for　variations　in　earth’s　weather。　thanks　almost　entirely　to　croll’s　persuasivetheory；　people　in　britain　began　to　bee　more　responsive　to　the　notion　that　at　some　formertime　parts　of　the　earth　had　been　in　the　grip　of　ice。　when　his　ingenuity　and　aptitude　wererecognized；　croll　was　given　a　job　at　the　geological　survey　of　scotland　and　widely　honored：

he　was　made　a　fellow　of　the　royal　society　in　london　and　of　the　new　york　academy　ofscience　and　given　an　honorary　degree　from　the　university　of　st。　andrews；　among　much　else。

unfortunately；　just　as　agassiz’s　theory　was　at　last　beginning　to　find　converts　in　europe；　hewas　busy　taking　it　into　ever　more　exotic　territory　in　america。　he　began　to　find　evidence　forglaciers　practically　everywhere　he　looked；　including　near　the　equator。　eventually　he　becameconvinced　that　ice　had　once　covered　the　whole　earth；　extinguishing　all　life；　which　god　hadthen　re…created。　none　of　the　evidence　agassiz　cited　supported　such　a　view。　nonetheless；　inhis　adopted　country　his　stature　grew　and　grew　until　he　was　regarded　as　only　slightly　below　adeity。　when　he　died　in　1873　harvard　felt　it　necessary　to　appoint　three　professors　to　take　hisplace。

yet；　as　sometimes　happens；　his　theories　fell　swiftly　out　of　fashion。　less　than　a　decade　afterhis　death　his　successor　in　the　chair　of　geology　at　harvard　wrote　that　the　“so…called　glacialepoch　。　。　。　so　popular　a　few　years　ago　among　glacial　geologists　may　now　be　rejected　withouthesitation。”

part　of　the　problem　was　that　croll’s　putations　suggested　that　the　most　recent　ice　ageoccurred　eighty　thousand　years　ago；　whereas　the　geological　evidence　increasingly　indicatedthat　earth　had　undergone　some　sort　of　dramatic　perturbation　much　more　recently　than　that。

without　a　plausible　explanation　for　what　might　have　provoked　an　ice　age；　the　whole　theoryfell　into　abeyance。　there　it　might　have　remained　for　some　time　except　that　in　the　early　1900sa　serbian　academic　named　milutin　milankovitch；　who　had　no　background　in　celestial　motionsat　all—he　was　a　mechanical　engineer　by　training—developed　an　unexpected　interest　in　thematter。　milankovitch　realized　that　the　problem　with　croll’s　theory　was　not　that　it　wasincorrect　but　that　it　was　too　simple。

as　earth　moves　through　space；　it　is　subject　not　just　to　variations　in　the　length　and　shape　ofits　orbit；　but　also　to　rhythmic　shifts　in　its　angle　of　orientation　to　the　sun—its　tilt　and　pitch　andwobble—all　affecting　the　length　and　intensity　of　sunlight　falling　on　any　patch　of　land。　inparticular　it　is　subject　to　three　changes　in　position；　known　formally　as　its　obliquity；precession；　and　eccentricity；　over　long　periods　of　time。　milankovitch　wondered　if　there　mightbe　a　relationship　between　these　plex　cycles　and　the　ings　and　goings　of　ice　ages。　thedifficulty　was　that　the　cycles　were　of　widely　different　lengths—of　approximately　20；000；40；000；　a