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1、THENOBELPRIZEINPHYSICS2015POPULARSCIENCEBACKGROUNDThechameleonsofspaceTheysolvedtheneutrinopuzzleandopenedanewrealminparticlephysics.TakaakiKajitaandArthurB.McDonaldwerekeyscientistsoftwolargeresearchgroups,Super-KamiokandeandSudburyNeutrinoObservatory,whichdiscov
2、eredtheneutrinosmid-flightmetamorphosis.Thehuntwason–deepinsidetheEarthingiganticfacilitieswherethousandsofartificialeyeswaitedfortherightmomenttouncoverthesecretsofneutrinos.In1998,TakaakiKajitapresentedthediscoverythatneutrinosseemtoundergometamorphosis;theyswit
3、chidentitiesontheirwaytotheSuper-Kamiokandedetec-torinJapan.TheneutrinoscapturedtherearecreatedinreactionsbetweencosmicraysandtheEarth’satmosphere.Tornbetweenidentities–tau-,electron-ormyon-neutrino?Meanwhile,ontheothersideoftheglobe,scientistsattheSudburyNeutrino
4、ObservatoryinCanada,SNO,werestudyingneutrinoscomingfromtheSun.In2001,theresearchgroupledbyArthurB.McDonaldprovedthattheseneutrinos,too,switchidentities.Together,thetwoexperimentshavediscoveredanewphenomenon–neutrinooscillations.Afar-reachingconclusionoftheexperime
5、ntsisthattheneutrino,foralongtimeconsideredtobemassless,musthaveamass.Thisisofground-breakingimportanceforparticlephysicsandforourunderstandingoftheuniverse.ReluctantheroesWeliveinaworldofneutrinos.Thousandsofbillionsofneutrinosareflowingthroughyourbodyeverysecond
6、.Youcannotseethemandyoudonotfeelthem.Neutrinosrushthroughspacealmostatthespeedoflightandhardlyeverinteractwithmatter.Wheredotheycomefrom?SomewerecreatedalreadyintheBigBang,othersareconstantlybeingcreatedinvariousprocessesinspaceandonEarth–fromexplodingsupernovas,t
7、hedeathofmassivestars,toreactionsinnuclearpowerplantsandnaturallyoccurringradioactivedecays.Eveninsideourbodiesanaverageof5,000neutrinospersecondisreleasedwhenanisotopeofpotassiumdecays.ThemajorityofthosethatreachtheEarthoriginateinnuclearreactionsinsidetheSun.Sec
8、ondonlytoparticlesoflight,photons,theneutrinosarethemostnumerousparticlesintheentireuniverse.Foralongtime,however,theirexistencewasnotevencertain.Quitet
