Wikipedia: Copenhagen interpretation/Talk

The claim:

    When rolling a die, we use probabilites to describe the outcomes 
    because we don't have enough information even though we believe 
    that the whole process is deterministic.

isn't true if we accept the Copenhagen interpretation. A die roll is a chaotic process, and so is sensitive to initial conditions and tiny disturbances during the roll. Even thermal motion of atoms within it can affect the outcome. A die roll is just as deterministic or nondeterministic as the underlying quantum mechanics.

A better example of deterministic probabilities would be yesterday's lottery results, if I don't yet know the results. The winner has already been chosen, so awarding the prize will be deterministic. But I can still calculate the probability that I'll get the prize, because of my ignorance of the hidden state.

The point is well taken. However I don't like your example very much, because it adds the feature of past tense which confuses matters. How about this: "In classical physics, probabilities were used to describe the outcome of rolling a die, even though the proceess was thought to be completely deterministic. Probabilities served as a substitute for complete information." --AxelBoldt

Sure. That sounds good.

The text says that Aspect's experiment "confirmed the Copenhagen interpretation", which might be interpreted to mean that it disconfirmed the many-worlds interpretation or some others, when it did nothing of the sort. It merely confirmed that it is impossible to speak about the outcome of a measurement that isn't in fact made. Both interpretations of what that means are consistent with experiment, as are other interpretations (like "Decoherence"). --LDC

Good point, I'll fix it. Do you know anything about decoherence? --Axel

Decoherence isn't an interpretation in and of itself, it simply explains how the different parts of a wave function can disentangle themselves. You still need them to either disappear (Copenhagen) or persist (many-worlds).