Tim Thompson

2008-Dec-27, 07:40 PM

There have been several discussions over the interpretation of the expansion of space, whether or not we can say that space in physically, really expanding, or that it is only a coordinate system effect. I post this note only to draw the attention of anyone interested in the topic to the following recently posted paper:

Eppur si muove

Michał Chodorowski

arXiv: http://arxiv.org/abs/0812.3972

ADS: http://adsabs.harvard.edu/abs/2008arXiv0812.3972C

Abstract: In two recent papers, Abramowicz et al. claim that the expansion of the Universe can be interpreted only as the expansion of space. In fact, what they really prove is that the cosmological expansion cannot be described in terms of real motions in Minkowski spacetime. However, there is no controversy about this issue. Abramowicz et al. show that in general, the cosmological redshift is not a Doppler shift and they consider this fact as a proof that space expands. Again, nobody believes (perhaps except Milne) that for non-empty universes the origin of the redshift is purely Dopplerian. From the Principle of Equivalence it follows that there must be also a gravitational shift in presence of matter. Indeed, it is well known in cosmology that for small redshifts, the cosmological redshift can be decomposed into a Doppler component and a gravitational component. In a forthcoming paper, we shall perform such a decomposition for arbitrarily large values of the redshift.

The arXiv link leads to the abstract & a downloadable PDF preprint of the full paper. The ADS link allows access to references cited in the paper and to any papers which eventually cite this one, as well as including the arXiv link. It is interesting to me that the topic remains a matter of some controversy in the "real world", by which I mean the world of science outside the strange world of discussion boards.

Eppur si muove

Michał Chodorowski

arXiv: http://arxiv.org/abs/0812.3972

ADS: http://adsabs.harvard.edu/abs/2008arXiv0812.3972C

Abstract: In two recent papers, Abramowicz et al. claim that the expansion of the Universe can be interpreted only as the expansion of space. In fact, what they really prove is that the cosmological expansion cannot be described in terms of real motions in Minkowski spacetime. However, there is no controversy about this issue. Abramowicz et al. show that in general, the cosmological redshift is not a Doppler shift and they consider this fact as a proof that space expands. Again, nobody believes (perhaps except Milne) that for non-empty universes the origin of the redshift is purely Dopplerian. From the Principle of Equivalence it follows that there must be also a gravitational shift in presence of matter. Indeed, it is well known in cosmology that for small redshifts, the cosmological redshift can be decomposed into a Doppler component and a gravitational component. In a forthcoming paper, we shall perform such a decomposition for arbitrarily large values of the redshift.

The arXiv link leads to the abstract & a downloadable PDF preprint of the full paper. The ADS link allows access to references cited in the paper and to any papers which eventually cite this one, as well as including the arXiv link. It is interesting to me that the topic remains a matter of some controversy in the "real world", by which I mean the world of science outside the strange world of discussion boards.