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Science

Journal: Scientific "Theories"

Journal by Pi_0's don't shower

There have been a lot of people in the /. moderated forums who consistently get modded *up* for saying things like, "General Relativity is just a theory, not a law, and isn't really correct," or "Quantum Gravity will supersede General Relativity" or "Only String Theory has a chance to be a correct theory."

As a physicist-to-be, in my third year of grad school, I'd like to sound off on this erroneous thinking. When scientists say a theory is "correct", it means that within a certain regime, the theory accurately describes the behavior of the system. By this definition, Newton's theory of motion & gravitation is correct for small gravitational fields, slow velocities (much less than speed of light), and large distances (much greater than 1 angstrom).

Einstein's theory of gravity is correct in *all* physical regimes that we know about. Not some, not most, but all. No experiment has ever disagreed with a General Relativistic prediction. Quantum gravity or string theory may someday predict behavior in a system where GR cannot be used, such as at a singularity, but thus far those theories make no predictions, and cannot even reduce to GR in a classical limit.

Scientific Theories don't get promoted to laws, like you're taught in elementary school; they just get applied in a certain range. It does piss me off when people shoot off at the mouth about scientists not thinking outside the box and looking at other theories.... it's because there *are* no other adequate theories!

There is *no* alternative to GR, there is *no* alternative to the big bang, there is *no* alternative to QED, etc., that can 1) reproduce all the features that are known to be accurate descriptions of the universe, and 2) make new predictions that are discernable from the pre-existing theory. This is why I take issue with "Steinhardt and Turok's brane-world" scenario as an alternative to the big-bang with inflation, for instance, because it makes NO NEW PREDICTIONS, and is not distinguishable from what it seeks to replace. It's also why I take issue with MOND and alternative theories of gravity, because they DO NOT REPRODUCE KNOWN RESULTS.

I believe that is all I have for now.

Real Programmers don't write in PL/I. PL/I is for programmers who can't decide whether to write in COBOL or FORTRAN.

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