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1、Unit42 AnswertotheMysteryofLifeIsFour Scientistshavefoundasimplemathematicalrelationshipthatconnectsthewholenature,fromthetiniestcelltothevastforestoftheAmazon.Theconnectionsareallbasedonthethreedimensionsofthephysicalworld--length,depthandwidth--pluson
2、e,makingthenumber4."Fouristhemagicnumberoflife,"saysDr.GeoffreyWestoftheSantaFeInstituteinNewMexico,akeynotespeakerattheNZInstituteofPhysicsannualconferencelastweek. Dr.West,aBritish-bornphysicist,andUSecologistsJamesBrownandBrianEnquisthavefoundmorethan
3、50biologicalrelationships,suchasbetweenbodysizeandheartrate,whicharebasedonnumberstakentothepowerof1/4. MuchofthetheoryisbasedonmathematicsthatcanconfusethemindofanyonewhostruggledthroughSchoolCertificatemaths.Sufficetosaythatitcentersonequationsinvolvin
4、gsquarerootsandnumberstothepowerof1/4.Insimplemaths,saysDr.West,"ifyouare16timesbiggerthanyourdog,yourheartrateishalfthedog'srate."Averagebodysizeandlifetimearealsorelatedinthesameratio.Soinprinciple,ifyouare16timesthesizeofyourdog,youwilllivetwiceaslong.
5、Wedobetterthanthat,thankstomodernmedicine,buttheaveragelifetimeofpre-EuropeanMaoriwasaround30. Remarkably,combiningthesetworelationshipsmeansthattheheartofeverymammalbeatsroughlythesamenumberoftimesinitsaveragelifetime--around1.5billiontimes--regardlesso
6、fwhetheritisadogorahuman,amouseoranelephant.Theimplicationisclear--wecan'tbeatnature."Thissaysthatthereisamaximumlifespanforagivensize,"Dr.Westsays. Heandhiscolleagueshavefoundthatsimilar"quarter-power"rulesgoverneverykindoflifeonEarth,fromtherateatwhich
7、single-celledbacteriaabsorbenergytotheheightofthoseAmazontrees.Theybelievethisuniformityisbecauseeverylivingthingismadeupofdistributionnetworkscarryingblood,airandothernutrientsfirstthroughbigtubessuchastheaorticarteryandthenthroughasuccessionofsmallertub
8、estothecapillaries,whichfinallydistributethenutrientstocells.Withineachclassofthelaststageofthechain,species,suchasmammals,thesizeofthecapillaries,isthesame.Soarethecellsthatweareallmadeof.Butastheorganismgetsbigger
