The topic of Arp's cosmology came up in another thread, which died aborning due to it not meeting PF guidelines. I would like to remedy that by introducing a more serious thread which will avoid the guideline issues. My information about Arp comes from the peer reviewed paper http://adsabs.harvard.edu/abs/1996ApJ...473..806K This states in part: So I would make the following observations, based on this paper - but since I'm not intimately familiar with Arp's cosmology, I would appreciate input if I'm missing or misrepresenting anything as far as the "mainstream" position goes. 1) Arp's evidence could best be characterized as suggestive, as opposed to "conclusive". Other scientists have looked seriously at his idea that the red-shift of quasars could be due to high peculiar velocities (i.e. velocity relative to the CMB frame), but this idea hasn't panned out due to a lack of corroborating evidence. The current theory (AFAIK) is that quasars are black holes at the center of galaxies. (I'd post references for this if I had them to hand to hand, but I don't.) 2) Arp himself doesn't (AFAIK) have any quarrel with the big bang theory, and is not proposing any sort of "tired light" theory. The red shift just cannot be explained by tired light (see for instance Ned Wright's page on tired light which quotes the appropriate references). It has to be explained by velocity in order for high-redshift supernovae explosions to occur in "slow motion" (over longer times) than low-redshift supernovae explosions.