List of physics phenomena9/2/2023 To say this is "fundamental" is to say that it is impossible to explain these probabilities as just arising from our lack of knowledge of some underlying definite variables, i.e. The quantum state is not a list of numbers with definite values for properties we can measure, it is merely a list of probabilities. So "fundamental randomness" really is supposed to mean "no hidden variables" - before you measured a particle's momentum, it didn't have a definite one. (Hunting for and closing "loopholes" in our experiments that might make it possible to argue we don't actually observe the violations of the Bell inequalities that rule out local hidden variable theories is a somewhat active niche I won't get into here.) No such theory can ever predict the results that we do, in fact, observe. The belief that there is a definite value for each property at all times is also called realism.īell's theorem says that quantum mechanics is incompatible with local hidden variable theories. The "randomness" is just because humans are extremely bad at the level of consistency required to flip it "in the same way" again. When you flip a classical coin in the exact same way, it will always yield the same result. "Randomness" in this classical world is incidental, arising from incomplete knowledge, imperfect measurement devices, etc. When people talk about "fundamental" or "inherent" randomness in the context of quantum mechanics, the technical meaning behind this is Bell's theorem, which tells us that there are no local hidden variable theories explaining the results of quantum mechanics.Ī "local hidden variable" theory is basically the classical idea of how the world works - everything has a list of well-defined properties, like position or momentum, and there is a "true" precise value for each of these at each time, and the laws of physics in principle determine the precise value at each other time from those at one instant.
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