Re: parallel universes

[John Clement <clement@HAL-PC.ORG>]

If you read the article carefully, the parallel universe is only really
invoked to explain how you can get interference results when you send
photons through singly.  The classical wave model result has no puzzling
results which might tempt one to postulate a "hidden variable" theory to
explain the results.

It is only when you look at single quanta that the results can "seem
contradictory".  The standard quantum theory works quite nicely, but some
people may find it uncomfortable.  By invoking hidden machinery such as a
parallel universe, you can do away with the "uncertainty" in quantum
mechanics, and make a theory which some may consider to be more comfortable.
However most of these theories have variables which can not be tested.
Indeed there are many such possible theories, but it is usually impossible
to test them to prove one is right and the others wrong.  As a result the
"standard model" is considered to be the better choice.  We appeal to the
philosophical principle called Occam's razor and shave off complications so
that we only end up with the simplest model.

Now it may be possible in the future to distinguish experimentally between
some of these hidden variable theories and to show that one of them is a
better choice.  Until then they remain speculative, and unproven or
undisproven.  They are certainly interesting.  Some of these hidden variable
theories have been around a long time and have been written by some well
known physicists such as David Bohm.  He actually wrote convincing arguments
on both sides of the issue.

I think the parallel universe invoked in the web article is very different
from parallel universes and extra dimensions invoked in the string theories,
but I may be wrong there.  String theory is designed to produce a single
uniform theory, and not just to make quantum theory more comfortable.

Some people may put some of these hidden variable theories in the same class
as saying that you have invisible faeries and sprites causing the effects,
but most are serious attempts which end up not being accepted.  So your
impulse to teach "standard" theories is very good.  But sometimes a good
dose of speculative science or science fiction can be stimulative and
entertaining.  I would be very happy when my students bring these things up
because it is a sign that they are thinking and reading.

John M. Clement
Houston, TX

> I'm not sure what you're trying to say, Jim.  It seems odd to me that
> someone
> would explain interference patterns by postulating parallel universes.  I
> don't want my students to ignore it, but I want to be able to provide
> meaningful
> discusion.   In general, I prefer to teach "standard" theories.  We have
> discussed many times in class the possibility that physics teachers 100
> years from
> now will be teaching different theories as "standard."  Today, the models
> we
> use are the ones that seem to make the most sense, in that they make
> predictions that we can test, and which seem to test "true" rather than
> false.   It
> seems to me that the current "standard model" is one in which interference
> is
> explained by wave behavior rather than parallel universes, and I was
> simply asking
> for help when my kids want to know WHY the parallel universe model is not
> as
> useful a model.   At least as far as we know, today.  I have no problem
> with
> string theory being correct, but I also do not have any education in
> string
> theory (they didn't offer a course on that when I got my BA) and therefore
> can
> only give a superficial explanation of it when asked.