About Dialogue, Bohm, spirit, language and enquiry

To savour a flavour of what we will be talking about here, as in umami….

From SEED magazine The Reality Tests  by Joshua Roebke / June 4, 2008

  • “In 1935, from an idyllic corner of New Jersey, Einstein and two young collaborators began a different assault on quantum mechanics. Einstein, Podolsky, and Rosen (EPR) did not question the theory’s correctness, but rather its completeness. More than the notion that god might play dice, what most bothered Einstein were quantum mechanics’ implications for reality. As Einstein prosaically inquired once of a walking companion, “Do you really believe that the moon exists only when you look at it?”
  • The EPR paper begins by asserting that there’s a real world outside theories. “Any serious consideration of a physical theory must take into account the distinction between the objective reality, which is independent of any theory, and the physical concepts with which the theory operates.” If quantum mechanics is complete, then “every element of physical reality must have a counterpart in the physical theory.” EPR argued that objects must have preexisting values for measurable quantities and that this implied that certain elements of reality could not be determined by quantum mechanics. Einstein and his colleagues imagined two electrons that collide and fly apart. After the collision the electrons exist in a state of superposition of the possible values for their momenta. Mathematically and physically, it makes no sense to say that either electron has a definite momentum independent of the other before measurement; they are “entangled.” But when one electron’s momentum is measured, the value of the other’s is instantly known and the superpositions collapse. Once the momentum is known for a particle, we cannot measure its position. This element of reality is denied us by the uncertainty principle. Even stranger is that this occurs even when the electrons fly vast distances apart before measurement. Quantum mechanics still describes the electrons as a single system across space. Einstein could never stomach that an experiment at one electron would instantaneously affect the other.
  • In Copenhagen Bohr began an immediate response. It didn’t matter if particles might affect one another over vast distances, or that particles had no observable properties before they are observed. As Bohr later said, “There is no quantum world. There is only an abstract quantum physical description.” Physicists’ discourse on reality began just as the world slid inexorably toward war. During WWII physicists once interested in philosophy worried about other issues. David Bohm, however, did worry. After the war Bohm was a professor at Princeton, where he wrote a famous textbook on quantum mechanics. Einstein thought it was the best presentation of quantum mechanics he had read, and when Bohm began to challenge the theory, Einstein said, “If anyone can do it, then it will be Bohm.”
  • In 1952, during the Red Scare, Bohm moved to Brazil. There he discovered a theory in which a particle’s position was determined by a “hidden variable” even when its momentum was absolutely known. To Bohm reality was important, and so to preserve it, he was willing to abandon locality and accept that entangled particles influenced one another over vast distances. However, Bohm’s hidden variables theory made the same predictions as quantum mechanics, which already worked.
  • In America Bohm’s theory was ignored. But when the Irishman John Bell read Bohm’s idea, he said, “I saw the impossible done.” Bell thought hidden variables might show quantum mechanics incomplete. Starting from Bohm’s work, Bell derived another kind of hidden variables theory that could make predictions different from those of quantum mechanics. The theories could be tested against one another in an EPR-type experiment. But Bell made two assumptions that quantum mechanics does not; the world is local (no distant influences) and real (preexisting properties). If quantum mechanics were correct, one or both of these assumptions were false, though Bell’s theorem could not determine which. Bell’s work on local hidden variables theory stirred little interest until the 1970s, when groups lead by John Clauser, Abner Shimony, and others devised experimental schemes in which the idea could be tested with light’s polarizations instead of electrons’ momentum. Then in 1982 a young Frenchman named Alain Aspect performed a rigorous test of Bell’s theory on which most physicists finally agreed. Quantum mechanics was correct, and either locality or realism was fundamentally wrong”
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