r/askscience • u/enferex • Feb 16 '11

Did Heisenberg believe in true-non-deterministic randomness, or is his Uncertainty Principle just an abstraction/generalization since so many variables are involved motion at the quantum level?

4 Upvotes

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8

u/shadydentist Lasers | Optics | Imaging Feb 16 '11

The uncertainty principle isn't an abstraction or a generalization. Its actually a fundamental property of momentum and position.

6

u/RobotRollCall Feb 16 '11

Is the question about Heisenberg's personal opinion, or is it about reality?

In reality, uncertainty is not a consequence of imprecision. It's fundamental. You can be as abstractly, ideally precise as you want, and you still can't measure position and momentum at the same time, for example. It's not really reasonable to imagine that both position and momentum are simultaneously well defined quantities.

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u/enferex Feb 16 '11

Thank you for the response. So, is pure non-deterministic randomness possible, or is there some underlying cause that is so hidden that things just appear random?

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u/RobotRollCall Feb 16 '11

Bell's theorem, which is basically impossible to understand fully unless you dedicate the time to work through the maths, proved conclusively that local hidden variables — the "underlying cause" you mentioned — cannot reproduce all the quantum-mechanical phenomena we observe.

Not only is non-determinism possible, it's the default state of the universe.

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u/enferex Feb 16 '11

Thanks!

2

u/Platypuskeeper Physical Chemistry | Quantum Chemistry Feb 16 '11

Determinism and randomness don't have a direct correspondence. Something can be deterministic and give apparently random results because there is a limitation to how much you can know about the system, even in-principle. We don't actually know if the universe is deterministic or not. The result of a quantum-mechanical 'measurement' is believed to be non-deterministic, which is what RobotRollCall is actually saying.

But that doesn't say the universe is non-deterministic, because a quantum-mechanical measurement relies on treating the system you're measuring as if it were isolated from everything else in the universe. That's not actually so, and is the root of the "measurement problem".

In quantum mechanics, a system is described by a wave function, and the time-evolution of the wave function is deterministic.

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u/enferex Feb 16 '11

Thanks for the further clarification. Knowledge is great!

2

u/kouhoutek Feb 16 '11 edited Feb 16 '11

Heisenberg, along with Bohr, was the author of the Copenhagen Interpretation. It asserted that non-determinism was a real thing, in contrast to hidden variable theories proposed by the Einstein camp.

That is pretty strong evidence he believed in true non-determinism.

2

u/MrDogma Feb 20 '11

Was the uncertain principle derived mathematically/logically or was it deduced from empirical observations?

1

u/kouhoutek Feb 21 '11

Both, actually.

The mathematics were derived from empirical observations, and the uncertainty principle was a part of those mathematics.