Everett thoughts are "trivially true", says Hawking.


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送交者: 短江学者 于 2015-03-23, 11:39:03:

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According to Everett, the laws of quantum mechanics dictate that the splitting observers will lead different lives in separate universes.

For decades, Everett and his classmates knew, physicists had been perplexed by the absence of a mathematical derivation of a single quantum reality from the multiple realities afforded by the Schrödinger Equation. To cope with this problem, physicists "postulated" that not all elements in a superposition are real. That must be true, they felt, because it accords with our experience: The only real element is the single one, the single world we see before us. We don't see multiple worlds superimposed on top of one another.

In the letter that appears here, Hugh Everett deemed this paradoxical "collapse" postulate "a philosophic monstrosity." Casting it aside, he decided to take the Schrödinger Equation at face value and work out what happens if there is no physical collapse. Everett considered the collection of all objects in the universe, including large or macroscopic systems (what we can see with the naked eye) to be fundamentally composed of atoms and molecules (microscopic quantum systems that we can't see). He suggested that these objects existed in ever-evolving superpositions without ever collapsing into a single reality, even though our reality suggests otherwise.

THE GEIGER COUNTER METAPHOR
Everett started handwriting his doctoral dissertation in the fall of 1954. His wife-to-be, Nancy Gore, began typing it up soon after they began dating in the summer of 1955. That September, Everett showed his thesis advisor at Princeton, the physicist John Wheeler, several typed excerpts of the larger work-in-progress. One excerpt, called "Probability in Wave Mechanics," introduced the idea that when two quantum systems interact, or exchange energy, the larger of the two systems automatically correlates with each element in the "related" superposed system.

In this scheme, a Geiger counter correlates with every physically possible instance of atomic decay that can be emitted from a radioactive metal (as opposed to measuring only one emission per instant). This makes logical sense, Everett said, because in a superposition, no single state is "privileged"—all possibilities are equally real. Of course, to us it seems as if the Geiger counter is registering only one decay at a time, instead of all possible decays simultaneously. But Everett argued that what actually occurs is that the Geiger counter "splits" into multiple instruments, each one registering one decay at one moment in time.

A human observer, however, sees the needle of the Geiger counter in only one position at a time, not "smeared" into multiple positions at a single moment. We do not see the needle simultaneously mirroring all of the possible energies of a radioactive particle flying off the metal at a given instant. Using the new science of information theory, Everett made a case that the observer does not see a "smear" because she herself has split, or "branched" into multiple observers (just as the amoeba does in his unpublished draft).

Each copy of the human observer is correlated with a possible event in the quantum system: radioactive metal-particle-Geiger counter-human observer. According to Everett, the laws of quantum mechanics dictate that the splitting observers will lead different lives in separate universes that continually branch off from interactions at the speed of light. Each branching universe creates a distinct record of its own history in the quantum environment.





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