Cranks take note: No-way physics
- From: Sam Wormley <swormley1@xxxxxxxxx>
- Date: Mon, 02 Jul 2007 02:35:26 GMT
No-way physics
http://physicsweb.org/articles/world/20/7/4
Critical Point: July 2007
Some principles of physics -- including the first two laws of
thermodynamics -- seem to invite rebellion.
Robert P Crease wonders why.
Many principles of physics are of the form "If you do this, what will
happen is that." Newton's second law, for example, says that the
acceleration of a particular mass will be proportional to the force
applied to it. Such principles imply that certain effects are
practically impossible. A small number of principles, however, belong
to a different category. These say, in effect, "That cannot happen."
Such principles imply that certain effects are physically impossible.
Notorious examples of the latter include the first two laws of
thermodynamics. The first law says that energy cannot be created or
destroyed ("You can't win"), while the second can be stated in several
forms, such as that heat cannot be transferred from a colder to a
warmer body or that the entropy of a closed system always increases
("You can't break even, either"). Other examples include Heisenberg's
uncertainty principle and the relativity principles regarding the
impossibility of recognizing absolute velocity and the prohibition of
faster-than-light travel.
Such principles often represent not "new physics" but deductions from
other principles. What is different about them is their form. And to
say that something is physically impossible tends to make scientists
want to rebel.
No way
The physics of impossibility goes by several names. "Forget-about-it"
physics is one; "noway" physics is another. Half a century ago, the
mathematician and historian of science Sir Edmund Whittaker referred to
"postulates of impotence", which assert "the impossibility of achieving
something, even though there may be an infinite number of ways of
trying to achieve it".
"A postulate of impotence", Whittaker wrote, "is not the direct result
of an experiment, or of any finite number of experiments; it does not
mention any measurement, or any numerical relation or analytical
equation; it is the assertion of a conviction, that all attempts to do
a certain thing, however made, are bound to fail."
Postulates of impotence thus resemble neither experimental facts nor
mathematical statements true by definition. Nevertheless, such
postulates are fundamental to science. Thermodynamics, Whittaker said,
may be regarded as a set of deductions from its postulates of
impotence: the conservation of energy and of entropy. It may well be
possible, he argued, that in the distant future each branch of science
will be able to be presented, à la Euclid's Elements, as grounded in
its appropriate postulate of impotence.
Contrarians
But no-way physics is important to science for another reason: it
attracts contrarians. I am not talking about the endless attempts by
frauds and naifs to get round the laws of thermodynamics by creating
perpetual-motion machines. Rather, I mean serious physicists who find
no-way physics a challenge to devise loopholes. In seeking these
loopholes, they end up clarifying the foundations of the field.
Contrarian physicists played a key role in both the discovery and the
interpretation of the uncertainty principle. In 1926 Werner Heisenberg
was promoting his new matrix mechanics -- a purely formal approach
to atomic physics -- by claiming that physicists had to abandon all
hope of observing classical properties such as space and time. Pascual
Jordan played the contrarian by devising a thought experiment to get
round such claims.
Jordan argued that if one could freeze a microscope to absolute zero,
then it should be possible to measure the exact position of an
electron, say, or the time of a quantum leap. This seems to have
inspired Heisenberg to think about the interaction between the
observing instrument and the observed situation, which led him to the
uncertainty principle. Jordan, the contrarian, forced Heisenberg to
think operationally rather than philosophically, and to clarify the
physics of the situation.
Another example of contrarian physics was James Clerk Maxwell's thought
experiment involving a tiny creature who operates a small door in a
partition inside a sealed box. By opening and shutting the door, the
"demon" -- as it was later called -- lets all the faster-moving
molecules into one side of the partition, violating the second law of
thermodynamics by getting heat to flow to that side. The discussion of
this thought experiment helped to clarify the then-mysterious concepts
of thermodynamics.
The critical point
Heisenberg once wrote, "Almost every progress in science has been paid
for by a sacrifice, for almost every new intellectual achievement
previous positions and conceptions had to be given up. Thus, in a way,
the increase of knowledge and insight diminishes continually the
scientist's claim on 'understanding' nature."
Heisenberg is overstating the point: surely the advance of science
involves developing more subtle and complex concepts that encompass the
simpler existing ones. But these more subtle and complex concepts are
often produced by those who are dissatisfied by the prospect of having
to make the kind of sacrifice Heisenberg mentions.
Dissatisfaction is a powerful driving force in science, and it can
arise in many ways. Sometimes it springs from a scientist's sense that
a confusing heap of experimental data can be better organized. At other
times it arises from the feeling that a theory is too complicated and
can be simplified, or that its parts are not fitting together properly.
Still other dissatisfactions arise from mismatches between a theory's
predictions and experimental results.
No-way physics produces a special kind of dissatisfaction, involving
the collision of science with our hopes and dreams -- of limitless
energy, of superluminal travel, of pinning things to specific places at
specific times. Humans seem hard-wired to have such hopes, and
hard-wired to balk at the science that dashes them. Small wonder then
that no-way physics leaves them dissatisfied. But science wins in the
end.
.
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