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1、1二、FermiProblem OnaMondaymorninginJuly,theworld’sfirstatombombexplodedintheNewMexicodesert.Fortysecondslater,theshockwavesreachedthebasecampwheretheItalian—AmericanphysicistEnricoFermiandhisteamstood.Afteramentalcalculation,Fermiannouncedtohisteamth
2、atthebomb’senergyhadequated10,000tonsofTNT.Thebombteamwasimpressed,butnotsurprised.Fermi’sgeniuswasknownthroughoutthescientificworld.In1938hehadwonaNobelPrize.Fouryearslaterheproducedthefirstnuclearchainreaction,leadingusintothenuclearage.SinceFermi’sdeathi
3、n1954,nophysicisthasbeenatonceamasterexperimentalistandaleadingtheoretician. Likeallvirtuosos,Fermihadadistinctivestyle.Hepreferredthemostdirectroutetoananswer.Hewasverygoodatdividingdifficultproblemsintosmall,manageablebits—talentweallcanuseinourdail
4、ylives. Todevelopthistalentinhisstudents.FermiwouldsuggestatypeofquestionnowknownasaFermiproblem.Uponfirsthearingoneofthese,youhaven’ttheremotestnotionoftheanswer,andyoufeelcertainthattoolittleinformationhadbeengiventosolveit.Yetwhentheproblemisbroken
5、intosub—problems,eachanswerablewithoutthehelpofexpertsorbooks,youcancomeclosetotheexactsolution. SupposeyouwanttodetermineEarth’scircumferencewithoutlookingitup.EveryoneknowsthatNewYorkandLosAngelesareabout3,000milesapartandthatthetimedifferencebetwee
6、nthemisthreehours.Threehoursisone—eighthofaday,andadayisthetimeittakestheplanettocompleteonerotation,soitscircumferencemustbeeighttimes3,000or24,000miles.Thisanswerdiffersfromthetruevalue,24,902.45miles,bylessthanfourpercent. Ultimatelythevalueofdeali
7、ngwitheverydayproblemsthewayFermididliesintherewardsofmakingindependentdiscoveriesandinventions.Itdoesn’tmatterwhetherthediscoveryisasimportantasdeterminingthepowerofanatomorassmallasmeasuringthedistancebetweenNewYorkandLosAngeles.Lookinguptheanswer,orletti
8、ngsomeoneelsefindit,deprivesyouofthepleasureandpridethataccompanycreativity,anddeprivesyouofanexperiencethatbuildsupself—confidence.Thus,approachingpersonaldilemmasasFermiproblemscanbecomeahabitthatenr