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1、TOPTENUNSOLVEDPROBLEMSINPHYSICS1.Areallthe(measurable)dimensionlessparametersthatcharacterizethephysicaluniversecalculableinprincipleoraresomemerelydeterminedbyhistoricalorquantummechanicalaccidentanduncalculable?Einsteinputitmorecrisply:didGodhaveachoiceincreating
2、theuniverse?ImaginetheOldOnesittingathiscontrolconsole,preparingtosetofftheBigBang."HowfastshouldIsetthespeedoflight?""HowmuchchargeshouldIgivethislittlespeckcalledanelectron?""WhatvalueshouldIgivetoPlanck'sconstant,theparameterthatdeterminesthesizeofthetinypackets
3、--thequanta--inwhichenergyshallbeparceled?"Washerandomlydashingoffnumberstomeetadeadline?Ordothevalueshavetobewhattheyarebecauseofadeep,hiddenlogic?Thesekindsofquestionscometoapointwithaconundruminvolvingamysteriousnumbercalledalpha.Ifyousquarethechargeoftheelectro
4、nandthendivideitbythespeedoflighttimesPlanck'sconstant,allthedimensions(mass,timeanddistance)cancelout,yieldingaso-called"purenumber"--alpha,whichisjustslightlyover1/137.Butwhyisitnotprecisely1/137orsomeothervalueentirely?Physicistsandevenmysticshavetriedinvaintoex
5、plainwhy.2.Howcanquantumgravityhelpexplaintheoriginoftheuniverse?Twoofthegreattheoriesofmodernphysicsarethestandardmodel,whichusesquantummechanicstodescribethesubatomicparticlesandtheforcestheyobey,andgeneralrelativity,thetheoryofgravity.Physicistshavelonghopedthat
6、mergingthetwointoa"theoryofeverything"--quantumgravity--wouldyieldadeeperunderstandingoftheuniverse,includinghowitspontaneouslypoppedintoexistencewiththeBigBang.Theleadingcandidateforthismergerissuperstringtheory,orMtheory,asthelatest,souped-upversioniscalled(witht
7、heMstandingfor"magic,""mystery,"or"motherofalltheories").3.Whatisthelifetimeoftheprotonandhowdoweunderstandit?Itusedtobeconsideredgospelthatprotons,unlike,say,neutrons,liveforever,neverdecayingintosmallerpieces.Theninthe1970's,theoristsrealizedthattheircandidatesfo
8、ragrandunifiedtheory,mergingalltheforcesexceptgravity,impliedthatprotonsmustbeunstable.Waitlongenoughand,veryoccasionally,oneshouldbreakdown.Thet
