能量的来源(The source of Energy)

详细内容

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asummaryofthephysicalandchemicalnatureoflifemustbegin,notontheearth,butinthesun;infact,atthesun'sverycenter.itisherethatistobefoundthesourceoftheenergythatthesunconstantlypoursoutintospaceaslightandheat.

thisenergyislibratedatthecenterofthesunasbillionsuponbillionsofnucleiofhydrogenatomscollidewitheachotherandfusetogethertoformnucleiofhelium,andindoingso,releasesomeoftheenergythatisstoredinthenucleiofatoms.theoutputoflightandheatofthesunrequiresthatsome600milliontonsofhydrogenbeconvertedintoheliuminthesuneverysecond.thisthesunhasbeendoingforseveralthousandsofmillionsofyear.

thenuclearenergyisreleasedatthesun'scenterashigh-energygammaradiation,aformofelectromagicradiationlikelightandradiowaves,onlyofverymuchshorterwavelength.thisgammaradiationisabsorbedbyatomsinsidethesuntobereemittedatslightlylongerwavelengths.thisradiation,initsturnisabsorbedandreemitted.

astheenergyfiltersthroughthelayersofthesolarinterior,itpassesthroughthex-raypartofthespectrumeventuallybeinglight.atthisstage,ithasreachedwhatwecallthesolarsurface,andcanescapeintospacewithoutbeingabsorbedfurtherbysolaratoms.averysmallfractionofthesun'slightandheatisemittedinsuchdirectionsthatafterpassingunhinderedthroughinterplaaryspace,ithitstheearth.