A Short History of Nearly Everything-第29章

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rmans。”

as　it　was；　the　europeans　had　their　hands　full　trying　to　understand　the　strange　behavior　ofthe　electron。　the　principal　problem　they　faced　was　that　the　electron　sometimes　behaved　like　aparticle　and　sometimes　like　a　wave。　this　impossible　duality　drove　physicists　nearly　mad。　forthe　next　decade　all　across　europe　they　furiously　thought　and　scribbled　and　offered　petinghypotheses。　in　france；　prince　louis…victor　de　broglie；　the　scion　of　a　ducal　family；　found　thatcertain　anomalies　in　the　behavior　of　electrons　disappeared　when　one　regarded　them　as　waves。

the　observation　excited　the　attention　of　the　austrian　erwin　schr？dinger；　who　made　some　deftrefinements　and　devised　a　handy　system　called　wave　mechanics。　at　almost　the　same　time　thegerman　physicist　werner　heisenberg　came　up　with　a　peting　theory　called　matrixmechanics。　this　was　so　mathematically　plex　that　hardly　anyone　really　understood　it；including　heisenberg　himself　（“i　do　not　even　know　what　a　matrix　is　；”　heisenberg　despairedto　a　friend　at　one　point）；　but　it　did　seem　to　solve　certain　problems　that　schr？dinger’s　wavesfailed　to　explain。　the　upshot　is　that　physics　had　two　theories；　based　on　conflicting　premises；that　produced　the　same　results。　it　was　an　impossible　situation。

finally；　in　1926；　heisenberg　came　up　with　a　celebrated　promise；　producing　a　newdiscipline　that　came　to　be　known　as　quantum　mechanics。　at　the　heart　of　it　was　heisenberg’suncertainty　principle；　which　states　that　the　electron　is　a　particle　but　a　particle　that　can　bedescribed　in　terms　of　waves。　the　uncertainty　around　which　the　theory　is　built　is　that　we　canknow　the　path　an　electron　takes　as　it　moves　through　a　space　or　we　can　know　where　it　is　at　agiven　instant；　but　we　cannot　know　both。

3any　attempt　to　measure　one　will　unavoidably3there　is　a　little　uncertainty　about　the　use　of　the　word　uncertainty　in　regard　to　heisenbergs　principle。　michaelfrayn；　in　an　afterword　to　his　play　copenhagen；　notes　that　several　words　in　german…unsicherheit；　unscharfe；unbestimmtheit…have　been　used　by　various　translators；　but　that　none　quite　equates　to　the　english　uncertainty。

frayn　suggests　that　indeterminacy　would　be　a　better　word　for　the　principle　and　indeterminability　would　be　betterstill。

disturb　the　other。　this　isn’t　a　matter　of　simply　needing　more　precise　instruments；　it　is　animmutable　property　of　the　universe。

what　this　means　in　practice　is　that　you　can　never　predict　where　an　electron　will　be　at　anygiven　moment。　you　can　only　list　its　probability　of　being　there。　in　a　sense；　as　dennis　overbyehas　put　it；　an　electron　doesn’t　exist　until　it　is　observed。　or；　put　slightly　differently；　until　it　isobserved　an　electron　must　be　regarded　as　being　“at　once　everywhere　and　nowhere。”

if　this　seems　confusing；　you　may　take　some　fort　in　knowing　that　it　was　confusing　tophysicists；　too。　overbye　notes：　“bohr　once　mented　that　a　person　who　wasn’t　outraged　onfirst　hearing　about　quantum　theory　didn’t　understand　what　had　been　said。”　heisenberg；　whenasked　how　one　could　envision　an　atom；　replied：　“don’t　try。”

so　the　atom　turned　out　to　be　quite　unlike　the　image　that　most　people　had　created。　theelectron　doesn’t　fly　around　the　nucleus　like　a　planet　around　its　sun；　but　instead　takes　on　themore　amorphous　aspect　of　a　cloud。　the　“shell”　of　an　atom　isn’t　some　hard　shiny　casing；　asillustrations　sometimes　encourage　us　to　suppose；　but　simply　the　outermost　of　these　fuzzyelectron　clouds。　the　cloud　itself　is　essentially　just　a　zone　of　statistical　probability　marking　thearea　beyond　which　the　electron　only　very　seldom　strays。　thus　an　atom；　if　you　could　see　it；would　look　more　like　a　very　fuzzy　tennis　ball　than　a　hard…edged　metallic　sphere　（but　not　muchlike　either　or；　indeed；　like　anything　you’ve　ever　seen；　we　are；　after　all；　dealing　here　with　aworld　very　different　from　the　one　we　see　around　us）。

it　seemed　as　if　there　was　no　end　of　strangeness。　for　the　first　time；　as　james　trefil　has　put　it；scientists　had　encountered　“an　area　of　the　universe　that　our　brains　just　aren’t　wired　tounderstand。”　or　as　feynman　expressed　it；　“things　on　a　small　scale　behave　nothing　like　thingson　a　large　scale。”　as　physicists　delved　deeper；　they　realized　they　had　found　a　world　where　notonly　could　electrons　jump　from　one　orbit　to　another　without　traveling　across　any　interveningspace；　but　matter　could　pop　into　existence　from　nothing　at　all—“provided；”　in　the　words　ofalan　lightman　of　mit；　“it　disappears　again　with　sufficient　haste。”

perhaps　the　most　arresting　of　quantum　improbabilities　is　the　idea；　arising　from　wolfgangpauli’s　exclusion　principle　of　1925；　that　the　subatomic　particles　in　certain　pairs；　even　whenseparated　by　the　most　considerable　distances；　can　each　instantly　“know”　what　the　other　isdoing。　particles　have　a　quality　known　as　spin　and；　according　to　quantum　theory；　the　momentyou　determine　the　spin　of　one　particle；　its　sister　particle；　no　matter　how　distant　away；　willimmediately　begin　spinning　in　the　opposite　direction　and　at　the　same　rate。

it　is　as　if；　in　the　words　of　the　science　writer　lawrence　joseph；　you　had　two　identical　poolballs；　one　in　ohio　and　the　other　in　fiji；　and　the　instant　you　sent　one　spinning　the　other　wouldimmediately　spin　in　a　contrary　direction　at　precisely　the　same　speed。　remarkably；　thephenomenon　was　proved　in　1997　when　physicists　at　the　university　of　geneva　sent　photonsseven　miles　in　opposite　directions　and　demonstrated　that　interfering　with　one　provoked　aninstantaneous　response　in　the　other。

things　reached　such　a　pitch　that　at　one　conference　bohr　remarked　of　a　new　theory　that　thequestion　was　not　whether　it　was　crazy；　but　whether　it　was　crazy　enough。　to　illustrate　thenonintuitive　nature　of　the　quantum　world；　schr？dinger　offered　a　famous　thought　experimentin　which　a　hypothetical　cat　was　placed　in　a　box　with　one　atom　of　a　radioactive　substanceattached　to　a　vial　of　hydrocyanic　acid。　if　the　particle　degraded　within　an　hour；　it　would　triggera　mechanism　that　would　break　the　vial　and　poison　the　cat。　if　not；　the　cat　would　live。　but　wecould　not　know　which　was　the　case；　so　there　was　no　choice；　scientifically；　but　to　regard　thecat　as　100　percent　alive　and　100　percent　dead　at　the　same　time。　this　means；　as　stephenhawking　has　observed　with　a　touch　of　understandable　excitement；　that　one　cannot　“predictfuture　events　exactly　if　one　cannot　even　measure　the　present　state　of　the　universe　precisely！”

because　of　its　oddities；　many　physicists　disliked　quantum　theory；　or　at　least　certain　aspectsof　it；　and　none　more　so　than　einstein。　this　was　more　than　a　little　ironic　since　it　was　he；　in　hisannus　mirabilis　of　1905；　who　had　so　persuasively　explained　how　photons　of　light　couldsometimes　behave　like　particles　and　sometimes　like　waves—the　notion　at　the　very　heart　of　thenew　physics。　“quantum　theory　is　very　worthy　of　regard；”　he　observed　politely；　but　he　reallydidn’t　like　it。　“god　doesn’t　play　dice；”　he　said。

4einstein　couldn’t　bear　the　notion　that　god　could　create　a　universe　in　which　some　thingswere　forever　unknowable。　moreover；　the　idea　of　action　at　a　distance—that　one　particle　couldinstantaneously　influence　another　trillions　of　miles　away—was　a　stark　violation　of　the　specialtheory　of　relativity。　this　expressly　decreed　that　nothing　could　outrace　the　speed　of　light　andyet　here　were　physicists　insisting　that；　somehow；　at　the　subatomic　level；　information　could。

（no　one；　incidentally；　has　ever　explained　how　the　particles　achieve　this　feat。　scientists　havedealt　with　this　problem；　according　to　the　physicist　yakir　aharanov；　“by　not　thinking　aboutit。”）above　all；　there　was　the　problem　that　quantum　physics　introduced　a　level　of　untidiness　thathadn’t　previously　existed。　suddenly　you　needed　two　sets　of　laws　to　explain　the　behavior　ofthe　universe—quantum　theory　for　the　world　of　the　very　small　and　relativity　for　the　largeruniverse　beyond。　the　gravity　of　relativity　theory　was　brilliant　at　explaining　why　planetsorbited　suns　or　why　galaxies　tended　to　cluster；　but　turned　out　to　have　no　influence　at　all　at　theparticle　level。　to　explain　what　kept　atoms　together；　other　forces　were　needed；　and　in　the1930s　two　were　discovered：　the　strong　nuclear　force　and　weak　nuclear　force。　the　strong　forcebinds　atoms　together；　it’s　what　allows　protons　to　bed　down　together　in　the　nucleus。　the　weakforce　engages　in　more　miscellaneous　tasks；　mostly　to　do　with　controlling　the　rates　of　certainsorts　of　radioactive　decay。

the　weak　nuclear　force；　despite　its　name；　is　ten　billion　billion　billion　times　stronger　thangravity；　and　the　strong　nuclear　force　is　more　powerful　still—vastly　so；　in　fact—but　theirinfluence　extends　to　only　the　tiniest　distances。　the　grip　of　the　strong　force　reaches　out　only　toabout　1/100；000　of　the　diameter　of　an　atom。　that’s　why　the　nuclei　of　atoms　are　so　pactedand　dense　and　why　elements　with　big；　crowded　nuclei　tend　to　be　so　unstable：　the　strong　forcejust　can’t　hold　on　to　all　the　protons。

the　upshot　of　all　this　is　that　physics　ended　up　with　two　bodies　of　laws—one　for　the　worldof　the　very　small；　one　for　the　universe　at　large—leading　quite　separate　lives。　einstein　dislikedthat；　too。　he　devoted　the　rest　of　his　life　to　searching　for　a　way　to　tie　up　these　loose　ends　byfinding　a　grand　unified　theory；　and　always　failed。　from　time　to　time　he　t