Heisenberg's uncertainty principle
In 'A brief History of Time' Hawkings explains, that Heisenberg's
uncertainty principle arises because you cannot observe a particle
without disturbing it, which is because you would need to 'touch' it
with something, like a photon or some other particle, and this will
transfer energy to the observed particle.
Further, says Hawkings: 'We could still imagine that there is a set
of laws that determines events completely for some supernatural being,
who could observe the present state of the universe without disturbing it'.
From this it would seem that the uncertainty principle is a sort of
'add on' to quantum mechanics, that has been added for practical reasons.
When I was introduced to quantum mechanics, it was stated as a basic
truth, maybe even THE basic TRUTH about the world: 'Everything is basicly
random, and it is only statistics that makes things look ordered'. But
would it not be more 'fair' to say that the uncertainty principle is
simply a way of taking into account the insecurity our observation
introduces to the measurement?
The observer is part of the observation.
Usually this is stated as: "the observer is part of the experiment."
Look for the book, Margins of Reality, by Robert Jahn; then tell me
what you think...
This has actually been a question of some interest in the philosophy
of quantum mechanics, and there are actually certain conditions
(Bell's inequalities) that predict quite different results for quantum
mechanics as normally understood and for the simplest theories that
assume an underlying determinism (so-called local theories). Experiments
have recently been done that show that the inequalities are actually
violated by the real world, meaning that at least these local deterministic
theories are wrong. But there could still be some kind of determinism
behind quantum mechanics - it is hard for us to find, at least!
In addition to the previous responses: It is incorrect to say that
the uncertainty principle is an "add-on" to quantum mechanics. Quantum
mechanics is a consequence of the uncertainty principle. I think that
the best explanation is in Heisenberg's little book "Physical Principles
of the Quantum Theory."
Jack L. Uretsky
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Update: June 2012