Quote:
Originally Posted by Dave2042
The difference between classical and quantum physics is that classical is deterministic.
...
In quantum physics, outcomes are only probabilistic. This is a result of (a) superimposition of complex wavefunctions (Schrodinger formalism) or equivalently (b) non-commutativity of operators (Heisenberg formalism).
...
Physics currently models the universe with two 'big' theories, quantum mechanics and general relativity. Each works wonderfully well in its range of applicability, however you wind up with problems where they both should apply (big bang, inside black holes).
...
The simple version is that GR always treats things as having definite values (including position) where QM says that plenty of things generally can't have definite values (position being one).
|
Hi Dave;
Good to have you aboard !
Thanks for having a go at distinguishing between the two 'domains' for us … I would agree, that they are classic 'textbook' distinctions.
Where I was originally coming from, is not so much the aspects of the models, which are "quantum mechanical" because they exclusively appear in 'quantum mechanics textbooks', but rather the aspects of the actual observed phenomena which result in those models (eg: like diffraction, discrete spectra etc). I'm fine with the respective 'domain labels' providing the distinctions .. we gotta have 'em in order to communicate clearly.
I appreciate what you have said, and this is not intended to counter any of it … rather I just want to reinforce the possibility that just because the models define and label things in these ways, it is still possible, and perfectly legitimate, to view these things in Classical ways. This wasn't really done conclusively in the past although as Steven mentioned, Bohr came up with a "classical/QM hybrid" which explained spectral lines (for example).
Thesedays, I suspect no-one bothers to attempt to do such (even though nowadays, it may be more fashionable to try) .. one is kind of left to ponder what might have happened had Classical models been reworked in the light of explaining these phenomena … the conclusion might well have been that there may not be as much disconnect in nature, as we are presently led to think.
The driving question is:
When do we know we are dealing with a "fundamentally quantum mechanical system"? .. observationally that is, from the phenomena themselves ?
Your words I underlined are interesting, as they seem to re-inforce our deterministic, Classically motivated expectations, that the domains we originally invented ourselves 'should' apply externally to the ranges we originally specified for them. I can see that this expectation may simply be of our own invention, and may not necessarily be the way nature works .. why should it be ?
Cheers