11-Multiverse - QuantumGravity, StringTheory, theAnthropic...

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Quantum Gravity, Q y, String Theory, e nthropic the Anthropic Principle and the Multiverse Biology 190A Lecture 11 ‐‐‐ Prof. Steve Schneider Dept. of Astronomy
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…from lecture 8—Schrödinger’s Cat If you can’t see into the box, is the cat alive, dead, or both at the same time until you open the box? When does the wavefunction collapse? Is the cat an observer, or does the whole design of the experiment already collapse the wavefunction?
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Einstein-Podolsky-Rosen (EPR)“Paradox” Proposed as a contradiction of quantum mechanics, but it has ended up as a strong proof of “entanglement.” Suppose a decay occurs that releases two electrons, and the rules of quantum mechanics require that the two electrons have opposite “spins” All experiments show that if you measure e two in the same the two in the same orientation, if one’s in ointed “up” spin is pointed up the other’s is “down”
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The EPR Experiment henever you measure e ins each particle always Whenever you measure the spins, each particle always “knows” the direction of the other’s spin seems as if the electrons carry a “hidden variable” It seems as if the electrons carry a hidden variable (spin direction) with them. If so, the EPR idea makes a prediction about what you will measure the spins at different angles (say left right, instead of up down) Quantum mechanics makes a different prediction— measurements in other directions will be no different than measuring the first particle again (Bell’s theorem) The Result? Quantum mechanics is right.
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Quantum Entanglement
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This note was uploaded on 11/22/2011 for the course BIOLOGY 190a taught by Professor Staff during the Fall '11 term at UMass (Amherst).

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11-Multiverse - QuantumGravity, StringTheory, theAnthropic...

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