From: "Wallace Polsom" <wallace-AT-raggedclaws.com>
Subject: BHA: Empirical evidence revisited
Date: Thu, 13 Jul 2000 12:43:58 -0600


Sorry, everyone, for the double message. Carelessness was the cause.

Colin writes:

> But, this proves nothing. As to why it's not the current dogma I don't
> know. But even if it were the dogma this wouldn't mean it's not right,
just
> as it's not wrong because it's not the dogma. Moreover, it may not be the
> dogma but  why so many theortical physicists are still interested in it.

The author of "A Theory of Everything?" gives a number of reasons why
theoretical physicists continue to be interested in string theory: (1) it
provides a possible solution to a hitherto intractable problem in physics,
namely, the apparent "incompatibility" of quantum mechanics and general
relativity; (2) it possesses the logical, aesthetic, and other qualities of
a good scientific theory; (3) it predicts the existence of entities that
physicists *might* soon be able to detect via experiments ("According to
supersymmetry the selectron's mass should be *identical* to that of the
electron. But no one has found a selectron. **Maybe this means that the
world is not supersymmetric, and therefore string theory is a fantasy**
[emphasis added]. The other possibility is simply that the masses of the
super-partners are larger than those of the regular particles, and our
accelerators are not powerful enough to create the super-particles. If this
is true it implies that the perfect symmetry between bosons and fermions,
called supersymmetry, does not manifest itself at our very low energies (or
large distance scales). If Nature is supersymmetric, that aspect of Nature
may only become apparent at fantastically high energies, when we expect all
the different forces to lose their identity and be subsumed into a unified
force. These energies are totally beyond the reach of forseable technology.
It is therefore unlikely that we shall ever see supersymmetry in its full
glory. But, remarkably, there are reasons to believe that a vestige of the
supersymmetry, namely, the super-particles, may be within reach of the next
round of experiments at Fermilab and at CERN---the European high energy
laboratory, in Geneva, Switzerland. That is, even though supersymmetry
itself may be beyond our reach the super-particles themselves may not be.");
and so on.

To return to the point of this discussion, however, I would argue that the
example of string theory suggests that Tobin is right, that "empirical
evidence is required for adjudication among **scientific** [emphasis added]
theories." As the author of "A Theory of Everything?" states, "Were we to
discover selectrons, for example, or gluinos, we would have discovered that
the world is fundamentally supersymmetric, at least at some sufficiently
high energy. This would be one of the most profound discoveries of science,
for it would be the first **evidence** [emphasis added] that spacetime has
more structure than we perceive directly."

>> Without experimental evidence, what is the status of string theory?

> Still under examination I suppose.

On this point, we agree.

> At what point in time do we reject a theory
> because there is little or no empirical evidence
> to support it?

Perhaps one ought to reject a theory that has no empirical support
whatsoever as soon as those who support the theory begin to claim that no
empirical support whatsoever is necessary. ;)

Cheers,
Wallace






     --- from list bhaskar-AT-lists.village.virginia.edu ---