Interpretation of the Cosmological Metric
Abstract
The cosmological Robertson-Walker metric of general relativity is often said to have the consequences that (1) the recessional velocity of a galaxy at proper distance obeys the Hubble law , and therefore galaxies at sufficiently great distance are receding faster than the speed of light ; (2) faster than light recession does not violate special relativity theory because the latter is not applicable to the cosmological problem, and because ``space itself is receding'' faster than at great distance, and it is velocity relative to local space that is limited by , not the velocity of distant objects relative to nearby ones; (3) we can see galaxies receding faster than the speed of light; and (4) the cosmological redshift is not a Doppler shift, but is due to a stretching of photon wavelength during propagation in an expanding universe. We present a particular Robertson-Walker metric (an empty universe metric) for which a coordinate transformation shows that none of these interpretation necessarily holds. The resulting paradoxes of interpretation lead to a deeper understanding of the meaning of the cosmological metric.
Cite
@article{arxiv.0803.2701,
title = {Interpretation of the Cosmological Metric},
author = {Richard J. Cook and M. Shane Burns},
journal= {arXiv preprint arXiv:0803.2701},
year = {2009}
}
Comments
REVTeX 4, 20 pages, accepted for publication in Am. J. Phys. Comments: edited version that will appear in the Am. J. Phys