Posted: Oct 07, 2011 3:17 pm
by twistor59
Teuton wrote:
twistor59 wrote:
Teuton wrote:But physical reality cannot be reduced to mere possibilities or probabilities. The real properties of spacetime points or regions must be actual determinate properties.

Emphasis mine. But that is the very heart and soul of quantum theory. A system might or might not possess a definite value of such a quantity until a measurement is made. In the cases were it does not possess a definite value, quantum theory is not making definite predictions about individual systems, but rather about ensembles of systems.

Physical reality is physical actuality and not a "semireal" limbo or twilight zone of mere possibilities, potentialities, or probabilities. Physical objects or systems must have some physical properties, since nothing can exist propertylessly; and I don't know what it means to say that they don't have definite, determinate properties unless physicists have measured them, i.e. that unmeasured physical reality swims in a sea of indeterminacy or vagueness.

It means that certain pairs observables are such that a system can't possess definite values of both observables simultaneously. If my system has a definite value of A, then B is indeterminate. The best I can do is say that if I have an ensemble of identically prepared systems, all with the same fixed value of A, then those systems will have a distribution of values of B. Quantum theory places some limits on how narrow that distribution can be.