🚀 go-pugleaf

How nice it is that a question asked by Connie (a high school teacher ?) is
at once answered by James (a theoretical physics researcher ?) and that we
can all join to debate the topic.

In the May 6 entry Connie wrote:

 > It seems we are now caught in a semantic argument, specifically:  what
 > does it mean to ask "why" in the context of physics.  One interpretation
 > is that "why" means "what is the cause".  Why does an object released from
 > rest above the earth's surface fall with constant acceleration? Because
 > that is its natural motion.  That was a satisfactory explanation for two
 > thousand years.  But Galileo and Newton's dissatisfaction produced new
 > theories, which in turn have made so much happen for us in the modern
 > world. These theories don't just make us happy- they empower us: and that
 > is the criterion by which we judge them valid.

To me it is not a semantic argument. To ask "why" in physics is to ask for
a satisfacory validation. What would be satisfactory to Richard Feynman may
not be satisfactory to me, or to my students. We do not have axioms (self
evident truths, as in mathematics) but commonly chosen facts, supported by
experimental data, used as if they were axioms. Attraction and repulsion
of charges, according to Coulomb's law, is one of these basic facts. The law
of universal gravitation, Newton's laws of motion, conservation of energy
and the law of refraction are also such facts.

To explain something in physics is to show conceptual links between basic
facts and the subject being discussed. At some level of sophistication, it
may be appropriate to remove the law of refraction from the list of "axioms"
but that does not mean that explaining optics in terms of experimentally
verifiable Snell's law is illogical. If we do not ask "why" then physics
bacomes factology. Too many "whys", on the other hand, can complicate
explanations to a point at which they becomes meaningless. As teachers we
are in the best position to decide what is and what is not appropriate
in a given situation.

It is nice to think about "truly ulimate causes" mentioned by Connie, but
fortunately, our daily work does not depend on the product of very advanced
speculations. Validating commonly accepted "axioms", and explaining things
in their terms, is challenging enough to make me happy when I succeed. I
wish the moment of happiness were more frequent, but that is another matter.