Re: Why is Quantum Mechanics so successful?
From: PD (pdraper_at_yahoo.com)
Date: 01/06/05
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Date: 6 Jan 2005 07:35:03 -0800
Lawrence wrote:
> I always heard it stated that Quantum Mechanics is the
> most successful of all sciences and it can survive
> till the end of time.
That's a subjective and nonsupportable statement. It does make a good
opener in a popular science book, though.
>
> I'd like to know in terms of what principles? I mean,
> is it about the electron orbitals and energy states?
> is it the wave function... in terms of the
probabilities/indeterminates
> descriptions? What?
There are so many examples of this, it's hard to point to just one.
The spectra of radiating atoms are *completely* unexplainable except
through a quantum-mechanical description. The shape of the spectrum for
blackbody radiation is *completely* unexplainable except through a
quantized description of radiation. The photoelectric effect is
*completely* unexplainable with a classical description of light. These
are not the most precisely tested successes of quantum mechanics, but
they are among the historical precedents.
>
> Can anyone show how quantum mechanics can solve
> a certain physical processes?
Sure. Try taking a quantum mechanics course. What I would suggest is
taking a mechanics course, then a very preliminary quantum course, then
a more advanced mechanics course that introduces conjugate variables,
then a course in classical E&M, then a more serious quantum course that
teaches you how quantum mechanics changes things with conjugate
variables and EM fields. Is there a short cut? No, not really. Any
short cut will leave you with the impression that you've learned more
than you really have.
>
> I've been reading about QM in books and webs but can't
> quite get it fully. Can anyone give an example of a
> calculation that involves the wave function, that
> no other techniques can.
The hydrogen spectrum.
>
> When someone would create a new hypothesis of atomic
> model. Why is the calculation of the compton differential
> cross section the ultimate test? Have scientists actually
> measured the value to 10 digit accuracy and owned the
> equipment to check it?
There is no ultimate test. There is a slew of tests which provide
overwhelming evidence in collection. In answer to your second question,
yes, groups of scientists have applied for, and received, funding
grants to build equipment precisely to measure certain quantities to
very high precision. They received this funding on the basis of their
reputations, the soundness of their proposal, and the central
importance of the experiment to the testing of theory or theories;
furthermore, with the understanding that their work will be thoroughly
checked and that they will publish their results with sufficient
transparency and completeness that other scientists will be able to
scrutinize their work and independently verify it.
>
> Last, why does quanta come in discrete values and
> not continuous?
That's what quanta mean: "lumps". If it were continuous, it wouldn't be
quantum mechanics. Why isn't nature continuous? Why is it lumpy? No one
knows why -- we just know that it is.
>
> These questions haunt me days and nights the past few
> weeks. Hope someone can assist. Don't miss each of
> the questions. Thanks a lot!
>
Haunting that doesn't lead to action is merely fretting or dreaming. If
you want answers, then do the work to find them. Seriously. A hobby is
something that interests you but which you put down when it starts to
become demanding. A calling is something you can't put down, no matter
how demanding it gets.
PD
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