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Re: Teaching science on the edge of knowledge



Dear Pamela-
You evidently didn't like my advice to avoid many of the issues
you raise with the answer, "I don't know, I haven't looked into it." So
let me give you the perspective of a guy who is exposed to this stuff on
an almost daily basis.
I am currently working on the equation of state of hot, dense,
pion clouds. While that doesn't take me into string theory or
supersymmetry, and barely touches on the standard model, I attend a couple
of seminars a week by people who are working in the two first-named
fields, Also, because of some sins of my youth, I have some interest in
string theory.
Supersymmetry deals with the expected spectrum of particles with
masses higher than any that can be produced with today's acceleerators.
The argument for supersymmetry (ofter made by Gordy Kane, Michigan) has to
do with the behavior of coupling constants as a function of energy. The
coupling of quarks to gluons, quarks to "gauge bosons", and electrons to
photons all coincide at a very high energy (called the Plank energy) in
theories that include supersymmetry (Gordy had an article in Physics Today
a few years ago). This fact fits into the notion that the universe, when
it was very hot, was extremely symmetric and all particles were massless.
As the universe cooled down, the symmetry broke "spontaneously",
and particles took on mass according to a "Higgs" mechanism (this is
roughly the behavior of a bar magnet in a weak magnetic field). The
virtue of this kind of theory is that it makes predictions giving upper
bounds on the mass of a particle called the "Higgs", to that such theories
are falsifiable - some have been falsified within the past few years.
String theory leads to the notion of extra-dimensions. In one
such theory the only interaction that senses the presense of the extra
dimensions is gravity. This is a nice theory, to my mind, because it does
two things. If reduces (depending on the number of dimensions) the
unification energy to well below the Plank energy - therefore providing a
counterexample to Kane's argument for Supersymmetry, and it makes
predictions about the strength of gravity at short distances. These
predictions are currenttly being tested, largely at the University of
Washington.
As for discomfort with the Universe, I too find it uncomfortable,
but I've decided to stick around for a while. Maybe the gods have
provided us with something that will ultimately turn out to be simple.
Best,
Jack


On Fri, 23 Jul 2004, Pamela L. Gay wrote:

re: crackpot theories vs alternative theories

Consider the following:
Supersymmetry, String Theory and The Standard Model do not completely
overlap, and are all trying to get toward *similar* things. If "The
Standard Model" is the standard thing to teach, then String Theory and
Supersymmetry are alternative theories. Are you really saying they are
crack pot theories? If they are crack pot theories, why exactly are we
building CERN's LHC?

In discussing the Big Bang, The Hartle-Hawking wave function describes
time as starting at the moment that space started; therefore there was
no time prior to to the Big Bang. At the same time, Andrei Linde has
worked on chaotic inflationary models that describe our universe as one
of many, and certainly not the first, that are forming a multiverse
(http://physics.stanford.edu/linde/) with time starting before our big
bang. Do we ignore Linde's work because it isn't Hartle-Hawkings theory?

I'm beginning to wonder if my astronomy background is causing me to run
into linguistical problems on this list serve. Astronomy is full of
instances where there is a main theory and three or four alternative
theories, and we're still waiting for the final word. Recently,
supernova research and WMAP proved the main theory was wrong and the
alternative theories (dark energy and modern inflation) were right. Is
physics such a mature field that it lacks these places where the main
theory is simply the most popular, but the data fits 3 or 4 theories
equally well?

Once you start getting into the realms of cosmology, particle physics
and the quest for the holy grail of quantum gravity there is no longer a
completely defined model to follow. And then there are the problems of
dark matter and dark energy. How comfortable are you living in a
universe where almost everything is made of something you can't see,
detect or describe? Can we leave ~90% of the universe out of our classroom?

The best of my students (and I'm including high school students I
volunteer with) show up in class having been exposed to multiple
theories in both particle physics and cosmology. When I asked how and
when you teach these topics, it was a real question. Giancoli has 5
chapters on particle physics and astrophysics. What do you do with these
chapters or the corresponding chapters in your books?

-Pamela





--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley