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Tuesday, October 11, 2005

Dark epicycles?  

From Physics Watch (via J.D. Watson at BrothersJudd ):
Determinations of the rotation speed of stars in galaxies (galactic rotation curves) based on the assumption that Newtonian gravity is a good approximation have led to the inference that a large amount of dark matter must be present - more than can be accounted for by non-luminous baryonic matter. ... Now F I Cooperstock and S Tieu of the University of Victoria have reworked the problem using general relativity in place of Newtonian gravity, and they find no need to assume the existence of a halo of exotic dark matter to fit the observed rotation curves.
Is it possible that dark matter may turn out to have as little reality as Ptolemaic epicycles, invented to make the math fit the observed facts within an outdated conceptual system?

Watson comments:
Modern astrophysics and cosmology have recently given us several "entities" which arise only from the need to somehow reconcile our current theories to observations: dark matter, dark energy, and inflation, none of which have any theoretical basis and are by definition unobservable except for their effects in the relevant equations. If dark matter is not only invisible but now possibly non-existent, what is the likely future of those other ad-hoc concepts?
When the facts don't fit the theory, there is an almost irrestible urge to invent complicated new explanatory corollaries to keep the theory anyway. See Lee Harris on Baran-Wallerstein.

posted by Kelly | 10:18 AM link