FIRTH%TARTAN@CMU-CS-C.ARPA@sri-unix.UUCP (08/21/83)
Should we look for Parallel Worlds? Sorry, folks, I cannot let the nonsense (as I believe it) from Patrick Wyant go unanswered. Occams principle (Entia non sunt multiplicanda praeter necessitatem) applies to principles of explanation, ie scientific hypotheses or theories. Such theories are constructions of the human mind: they are more noumena than phenomena. The idea of arbitrarily postulating parallel words is silly: if they exist, they are not theories but facts. The point at issue is this: of the many explanations of our present body of observations, are some simpler than others? Certainly so - Newton's theories are simpler than those of Copernicus, Einstein's simpler than Newton's (in the sense of making fewer postulates) and so on. In my judgement, the 'Relative State' theories of quantum phenomena are genuinely simpler than most others, in requiring fewer postulates. Now, if simpler theories in some way compel our conditional belief, we should believe also in their consequences - even those that happen never yet to have been observed. One of the consequences of the relative state theories is the existence (prediction, conjecture or whatever) of parallel worlds. They exist in the equations, which for me is sufficient reason to want to look for them. An a close parallel, consider Dirac's quantum field theory, and its construction (if you will) of the electron. The equations had two solutions, one describing electrons and another describing absurd particles with the mass of the electron but exactly opposite charge. The equations are plausible because they explain our observations, and credible because of their simplicity and elegance, so it is not sensible to complain that physics has got by until 1925 without having to postulate weird new particles: they are there in the equations, and, as Yukawa subsequently found, they are there in the universe. (By the way, if physicists today REALLY think there are only three dimensions, then they know less than Archimedes) Robert Firth -------