Saturday, April 23, 2011

Physics and hand-waving

If you are not a physicist but have any sense of physics, you probably think its unanswered questions lie on the frontiers, among the stars or within subatomic particles. That was certainly this non-physicist's impression before reading "The Man Behind the Curtain," Tony Rothman's essay in American Scientist. 'Tis not so. According to Rothman, the discussions in introductory physics textbooks and courses fail to remark upon, much less to explain, some quite deep open questions.
... friction produces heat and hence an increase in entropy. It thus distinguishes past from future. The increase in entropy—the second law of thermodynamics—is the only law of Nature that makes this fundamental distinction. Newton’s laws, those of electrodynamics, relativity … all are reversible: None care whether the universal clock runs forward or backward. If Newton’s laws are at the bottom of everything, then one should be able to derive the second law of thermodynamics from Newtonian mechanics, but this has never been satisfactorily accomplished and the incompatibility of the irreversible second law with the other fundamental theories remains perhaps the greatest paradox in all physics. It is blatantly dropped into the first days of a freshman course and the textbook authors bat not an eyelash.
Rothman cites several other examples of papered-over "holes" and claims others "abound throughout physics." His counsel is for physicists to distinguish between the accuracy with which they can describe what happens and the uncertainty that frequently bedevils their attempts to explain why it happens.

I'm generally adept at reproducing the twists and turns of a teacher's explanation, so I'm particularly susceptible to the sleights of hand a teacher can use to evade logical inconsistencies. If I had pursued physics as a major, I would very likely have acquired an understanding of it that was the equivalent of a safe path through a deadly swamp. It would have been suitable for passing on to others so they, too, could avoid falling into marshy pits, but it would have been less than useful for teaching how to drain those spots, that is, how to carry out the hard work of real physics research myself. And as Rothman remarks, "It seems to me that such an approach is both intellectually dishonest and fails to stimulate the habits of inquiry and skepticism that science is meant to engender." Hear, hear.

No comments:

Post a Comment