Re: what use of classical mechanics

From: Frank Hellmann (Certhas_at_gmail.com)
Date: 10/27/04 

Date: Wed, 27 Oct 2004 15:56:21 +0000 (UTC)

pdm190@hotmail.com (SunnyJing) wrote in message news:<46b99cc6.0410241513.555c302b@posting.google.com>...
> I am studying the course-a complete scheme of mechanics in 18th, 19th
> century, but I find it is just always denoted as "a passage to
> understand quantum mechanics", so it seems no practical use except
> leading to quantum mechanics.
> if so, why do people need to labor on it?

The simple answer: If you don't understand classical mechanics,
particularly in the Hamiltonian formalism you wont stand a chance in
QM or GR. The concept introduced there: Lagrangian and Hamiltonian
method, symmetries, and so on, are valid throughout physics. Plus
classical mechanics still describes and always will describe a vast
part of the world.

There are two boundaries of knowledge in physics: Simplicity and
complexity.

We can not yet simplify all phenomena into a common framework/theory.
We do not have a TOE.
Along the path to understanding this, learning classical mechanics is
but a stepping stone to quantum mechanics, GR and all the wonderfull
things ahead.

The other is complexity, in a sufficiently complex system (and
sufficiently complex is remarkably little: three gravitationally
interacting bodies in Newtons theory for example) we can write down
the equations of motion but we do not understand what they mean, what
they say and rpedict. This is also known as chaos theory.
Along the path of advancing this classical mechanics is (one of) the
(possible) framework(s) within which you work to find and reveal the
hidden and implicit structures that it holds. Check out the beautifull
KAM theorem for a taste of things on that boundary.

However, it sounds like your course is historical. Personally I favor
revisionist teaching. Teaching shouldn't be an accelerated rushing
through the historic development to the present point. Particularly if
it indeed contains no 20th century material it would obmitt Noethers
theorem which would be a crime.
If you want to see a good introduction to classical mechanics pick up
Landau Lifschitz, even though that two is somewhat old fashioned in
some aspects. 

----
frank

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