Laws, theories, principles, rules, equations, ...

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Tue, 7 Nov 2000, Chuck Britton wrote:

> We still talk about the 'Theory' of Relativity and of Evolution but
> Newton's 'Laws' of motion.
>
> Is it only elapsed time that transforms theories into laws? (If no
> DIS-proof is found)

I don't think "theories" are often transformed into "laws."  I
doubt that "F = dp/dt" was ever called "Newton's second theory."

In fact, I think there is very little to be gained in worrying
about the distinction, if any, between "laws" and "theories."  As
is the case with the words "push" and "pull," it won't be hard to
find violations of any definitions one might propose.
Nevertheless, I guess I tend to think of "laws" as being usually
more limited in scope and referring to specific quantitative
prescriptions like a = F/m, F = -kx, W + Q = delta E, and sin(a)/A
= sin(b)/B, or simply stated generalities like "planetary orbits
are ellipses," "an object in motion tends to stay in motion," "the
entropy of the universe monotonically increases," and "the worst
thing that can happen will" while "theories" are usually broader
in context--e.g., quantum theory, relativity theory, the theory of
evolution--and may encompass and unify a number of "laws."

On the other hand we have the Pauli exclusion "principle,"
Kirchhoff's "rules," and the Saha and Schroedinger "equations,"
all of which might be called "laws" in a parallel universe.  We
also have thermodynamics, classical mechanics, and geometrical
optics which seem a lot like "theories" but simply don't use the
name.

In any event it certainly has nothing to do with "proof" or even
falsification for that matter.  There are lots of useful "laws" in
physics that are well known not to be "true."  Furthermore, I
think it is interesting to note that the *most* fundamental "laws"
of physics are nothing more than apparent truths that we do not
understand.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm