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Re: [Phys-l] teaching different descriptions of "reality"



Brian Blais raises the question of introducing the concept of reality into physics teaching. I think students should be told that reality is a deep concept, and that we won't treat it in a physics class. It is a good topic for bull sessions, of course, as are sex, politics, and religion. Since the latter three classical topics are now considered to be improper for teacher-student intercourse, perhaps discussion of reality has some merit.

I have spent a great deal of time trying to define what I mean by reality, a subjective approach to the question. I have read what many others have had to say on that topic, and I conclude that it is a task that will ultimately prove fruitless. On rereading I have been unsatisfied with anything I have written on the topic. Many philosophers have written extensively on reality, which doesn't help, since I am seeking concision. Descartes's contribution, while concise, doesn't help, since I have never doubted my own reality. Nonetheless, reality seems to be the philosophers' game rather than the physicists'. Metaphysics, I have decided, is either not in the physicist's job description, or else is above his pay grade. I will note that no Physics Nobel Prize has ever been awarded for a description of reality *per se*. On the other hand, many Nobel Prizes have been awarded for proving the existence of an entity that previously had been realized only as the product of a theory.

Physics is the quantitative description of Nature. The description relates natural entities to one another in what seem to be elegant mathematical constructs we call "theories" and even "laws". These theories are mutually consistent, and they have predictive value. There are many candidates for true theories*, and there is agreement that a theory may be invalidated by demonstration that it fails to predict the result of an experiment correctly*. Thus physicists now consider mesons, antiparticles, and neutrinos to be real, and as I noted before, they have earned their discoverers many Nobel Prizes. (I think the neutrino epitomizes the tenuous nature of the physicist's hold on the nature of reality.)

Leigh

* "Truth" is another concept beyond the physicist's ken. Metaphysicians worry about truth, too. My own view is that, like reality, truth has no practical importance. I would substitute "valid" for "true", in the sense that a valid theory has not (perhaps "not yet") been invalidated in Nature.

** Note that this is a weaker requirement than Popper's requirement that a theory must be falsifiable. We now accept theories in astrophysics that cannot be falsified by observation or experiment because results of these are forever inaccessible. "Inflation" is one such theory.