The kinematic origin of the cosmological redshift
Abstract
A common belief about big-bang cosmology is that the cosmological redshift cannot be properly viewed as a Doppler shift (that is, as evidence for a recession velocity), but must be viewed in terms of the stretching of space. We argue that, contrary to this view, the most natural interpretation of the redshift is as a Doppler shift, or rather as the accumulation of many infinitesimal Doppler shifts. The stretching-of-space interpretation obscures a central idea of relativity, namely that it is always valid to choose a coordinate system that is locally Minkowskian. We show that an observed frequency shift in any spacetime can be interpreted either as a kinematic (Doppler) shift or a gravitational shift by imagining a suitable family of observers along the photon's path. In the context of the expanding universe the kinematic interpretation corresponds to a family of comoving observers and hence is more natural.
Cite
@article{arxiv.0808.1081,
title = {The kinematic origin of the cosmological redshift},
author = {Emory F. Bunn and David W. Hogg},
journal= {arXiv preprint arXiv:0808.1081},
year = {2010}
}
Comments
Accepted for publication in Am. J. Phys. Many small changes from previous version, but basic argument remains unchanged