From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: The size of electrons, and Fanciful misc SAGA
Date: 7 Nov 92 22:19:02 GMT
 <Nov.5.18.26.40.1992.16405@ruhets.rutgers.edu> <1992Nov6.142004.9208@prim>

dave@prim.demon.co.uk (Dave Griffiths) writes:

>Hmmm. Well I'm pretty keen to read _alternative_ theories of physics, so I
>don't like to see someone put down when they dare to suggest their crazy
>ideas, unless they're obviously a crackpot. Paul Koloc's article didn't set
>off my crackpot detector - he just seemed to be quoting fragments of some
>possibly well thought out theory.

Yes, maybe.  It would have been nice if he'd given references or
identified it as a theory he's been working out himself.

[...about the conservatism of physics...]

>At no (?) point has everything that went before
>been chucked out in favour of new model.

True-- though sometimes the foundations *do* get shaken.  The "old
quantum theory" of Bohr, Sommerfeld, et al.  was a series of very
ingenious patches to classical physics-- then, after a while, there
was a basic redefinition of what the theory was about, and suddenly
there was something *very* different from classical physics which
yielded classical physics almost as an epiphenomenon in certain
limits.  But things get imported from classical theory, via processes
of reinterpretation like canonical quantization.
 
>I'm a computer programmer by trade, and I've often come across the situation
>where a suite of programs has become large and unwieldy, so much new 
>functionality has been added that the structure is unstable. To make real
>progress you need to chuck the code away and redesign from scratch.

>It's just conceivable that physics has now reached that stage. That it's
>present form is no more than an historical accident. I'd love to see the
>theories of physics developed by alien civilizations.

Its present form in terms of notation, terminology, etc.  is
*certainly* a historical accident.  As for the underlying concepts,
I'm not sure.  I must echo your desire to see extraterrestrial
theories of physics.  It would be fascinating to see if they have
anything at all in common with our own.

As for the edifice becoming huge and unwieldy, it's not really that
bad, in the sense of there being lots and lots of ad hoc laws.  Pretty
much everything seems to fit into the framework of a theory with
two basic, currently ill-fitting parts:  classical general relativity,
with scalar curvature acting as Lagrangian density for the dynamics
of spacetime; and a gauge theory with three simple factors for the
gauge group, several kinds of spin-1/2 matter particles, and a
somewhat kludgey scalar particle.  This is too complicated to
look truly fundamental, but the trend over the last few decades
has, for the most part, been one of simplification.  We no longer
have to worry, for instance, about a proliferation of hadrons, and
all the interactions except those of the scalar (which there are 
good reasons to believe is *not* going to appear in better theories)
are implied by a single, extremely elegant principle, that of gauge
symmetry.

>There is no such thing as infinity. Physicists are going to have to bite
>the bullet and develop a discrete TOE at some time or other.

As John Baez said in some related context, I envy your certainty
in this matter.  Personally, I think it's a little more than a
coincidence that a good chunk of modern physics can be described
in terms of connections on various principal bundles, something
that would seem to bode ill for discrete theories.  But it would
be nice if a good discrete theory existed; it would certainly
solve some problems in quantum field theory.
-- 
Matt McIrvin
Newsgroups: sci.physics