From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: No big crunch?
Date: 6 Nov 1992 11:57 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
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In article <1992Nov5.212050.25373@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
> 
>     My guess is that there are far more assumptions in this than you
>     are letting on, many hidden.

Guess what you like.  You are free to read the papers and form a real 
scientific opinion, if you care to.

>     However, getting back on track it is silly to say that a theory that in 
>     some sense avoids internal inconsistency has passed some sort of 
>     valid scientific 'test'.  It's like patting oneself on the back
>     for not having assumed ii equals 3 and ii equals 5 at the same
>     time.  

Perhaps it seems that way to a mechanical engineer.  However, I assure you
that it really works that way in particle physics.  Internally consistent
theories come much more easily in classical physics than in quantum field
theory.  Over the fifty-odd years of particle physics history, internal 
consistency has repeatedly been a useful way of discovering new physics.

A classic example is the original Fermi paper on weak interactions.  This
is a paper that every physicist should read.  It's understandable, and the
power and clarity of Fermi's insight is just staggering, considering when
he wrote the paper.

In this paper, he writes down for the first time the form of the weak 
interaction Lagrangian, in effective form, i.e., as a four-fermion coupling
with a phenomenological coupling constant.  He realized that the data
was consistent with a current-current interaction, and constructs the
"Fermi Lagrangian" in analogy with electromagnetism.  

He points out in passing that if his Lagrangian is the correct low
energy expression then there probably exist massive weakly interacting
intermediate vector bosons.  Why?  Because his Lagrangian is mathematically
inconsistent at sufficiently high energy (roughly 300 GeV), and this is the
simplest way to "patch" it and save the theory.  

Roughly 45 years later, the W and Z were discovered, and were shown to have
all the properties that Fermi speculated they need have, only the basis
of mathematical consistency.  

Similar stories can be told about many other features of the standard
model.  Even those features which were predicted or discovered by different
means can be seen in hindsight to be *necessary* on the basis of 
consistency.  The charm quark is a good example.  Though is was predicted in 
order to explain the absence of flavor-changing neutral-current processes,
it is necessary mathematically in the SM to cancel anomalous diagrams 
which contain strange quarks.  Without it, the SM would blow up, i.e., lead
to infinite predictions in some embarassing places.

-Scott
--------------------
Scott I. Chase			"It is not a simple life to be a single cell,
SICHASE@CSA2.LBL.GOV		 although I have no right to say so, having
				 been a single cell so long ago myself that I 
				 have no memory at all of that stage of my 
				 life." - Lewis Thomas
Newsgroups: sci.physics