364 CHAPTER23. THEPROBLEMOFMEASUREMENT
oftheobjectinisolationfromtheobserver. Rather,thewavefunctionisacompact
representationoftheobserver’sinformationabouttheobservablesofagivenobject,
andmerelydescribesthepossibleoutcomeofaseriesofmeasurements. Putanother
way,thewavefunctiondoesnotreferto”physicalreality”perse,intheabsenceofan
observer;itservesonlytopredictandcorrellatemeasurements. Ifthereisnoobserver,
thennomeaningcanbeattachedtoaquantum-mechanicalwavefunction.Fromthis
pointof view,the”collapse”ofthewavefunctiondoesnotdescribeanewphysical
process;itisjustachangeintheinformationavailabletotheobserver,obtainedby
measurement.
ThemaincriticismthatcanbeleveledatBohr’sinterpretationisthatitbecomes
meaninglesstospeakofthephysicalstateofanobjectintheabsenceofanobserver.
How,then,can wedescribequantum-mechanical processes thatmayhaveoccured
innaturepriortothe evolutionofhumanbeings,or eventswhich,for onereason
oranother,mayhaveescapedhumanscrutiny? Inclassicalphysics,everyobjectin
theUniversehasaphysicalstate,adefinitepositionandmomentum,regardlessof
whetherornothumanbeingsarearoundtomeasurethatstate.Notsoforquantum
mechanics, at least in the Bohrinterpretation. Itisimpossible, inthis view, to
imaginethatanyobjectisinanydefinitequantumstate,withoutatleastanimplicit
referencetotheObserver.
Thefactthathumanobserversaresomehowanessentialfeatureofthequantum-
mechanicaldescriptionofnatureis,forsome,averytroublingaspectofBohr’sview.
Ingeneral,theCopenhageninterpretationhassomethingoftheflavoroflogicalpos-
itivism,aphilosophy whichholdsthatthepurposeof scienceisto correllatemea-
surements,ratherthandescribesome”objective”reality. ”Objectivereality,”inthe
positivistview,isameaninglessconcept,andscienceshouldbeformulatedentirely
intermsofquantitieswhichcanbemeasureddirectly. Thisview, inthehandsof
Machandothers,hadconsiderableinfluenceonphysicsintheearly20thcentury,and
certainlytheCopenhageninterpretationshowtracesofthisinfluence.
ItisalittledistressingtothinkthatscienceisnotaboutNature,butonlyabout
correllatingmeasurements. Still,theconsistencyoftheCopenhageninterpretation,
anditsabilitytoevadepuzzlesconnectedwiththeapparentnon-local”collapse”of
entangledwavefunctions,shouldnotbeunderestimated. Totheextentthatthereis
an”official”interpretationofquantumtheory,itwouldbetheCopenhagenview.
InPreparation: