a portionofthisvideowassponsoredbyNorton 360 Classicalmechanicsisgreat.
Ifyouknowthestateof a system, saythepositionandvelocityof a particle, thenyoucanuseanequationNewton's secondlaw, tocalculatewhatthatparticlewilldointhefuture.
Inquantummechanics.
Ifyouknowthequantumstateof a particlethatisitswavefunction, youcanusetheSchrodingerequationtocalculatewhatthatparticledointhefuture.
Withthispointlikeparticledetectionnow, I thinkit's understandablethatwhenthefoundersofquantumtheoryapproachthisproblem, theyconsideredthemeasurementMaurrielthanthewayfunction.
Afterall, themeasurementwassomethingwehadactuallyobserved, anditmatchesourexperienceof a worldofmatterparticles.
Add a radiationdetectorthattriggersthereleaseofpoisonouscyanidegasNow, althoughitwasonlymeantas a thoughtexperiment, Schrodingerhelpfullynotes, thisdevicemustbesecuredagainstdirectinterferencebythecat.
Soaftersometime, thewavefunctionofeverythinginsidetheboxesin a superpositionoftheatomhasnotdecayedpoisonnotreleasedCatAlivestateandtheAdamhasdecayedpoisonreleasedCatDeadState.
Sowhatwe'veseenissuperpositionisreallythesamethingasdescribingsystemswithwavesandentanglementmeansthatafterparticlesinteracttheredescribedby a singlewavefunction.
Well, then, intheSchrodinger's catthoughtexperiment, theradioactiveAdam, in a superpositionofdecayedandnotdecayed, getsentangledwiththedetectorandinturn, thecat.
Thewavefunctionisthecompletepictureofreality, andourmeasurementisjust a tinyfractionofit, thepartwebecomeentangledwithwhenweinteractwith a quantumobjectin a superposition, theuniversealsogoesbacktobeingdeterministic.
Butthere's a differencebetweentheenergyofthewholewayfunctionandtheenergythatpeopleineachbranchPercysoweshouldthinkofisnotduplicatingthewholeuniversebuttaking a certainamountofuniverseandsortofsubdividingit, slicingitintotwopieces.