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Message: <blockquote data-quote="Umbran" data-source="post: 9817069" data-attributes="member: 177">So, to start with, what do you mean by "legitimate"?  Noting that "legitimate" does not mean "correct in its conclusions".Articles in arXiv are not peer reviewed by that organization, if that's what you mean.  Unless this paper was also published by someone else who does such review, we don't have confidence that it has been given a lot of scrutiny.Moreover, this is in the "popular science" section of arXiv, and doesn't claim to be presenting new results or new science, but an interpretation.  Interpretations do not question data or established science.  They present ways of thinking about the established results.  Sometimes, this is to suggest what is physically happening, and sometimes it is just a source of inspiration for further investigation, "If we think of this as X, then that implies Y, which may be interesting," kind of stuff.And, at the end of the paper, they even say, "There is no “fact of the matter” about the interpretation of the cosmological redshift: what one concludes depends on one’s coordinate system or method of calculation."  So, they aren't even claiming to present a "fact" or "truth".One element of the paper I find odd is "Redshifts of nearby galaxies are Doppler shifts".  To which I say, "Yeah, but we already knew that."  Cosmological expansion does not occur within gravitationally bound (or, more strongly bound) systems.  All galaxies near us are part of the Local Group, which is gravitationally bound.  I suppose this discussion is useful in establishing the first step of their logic, but it isn't telling us anything interesting in and of itself.From there, they seem to take the position that since you can think of cosmological expansion in terms of covering the distance from A to B piecewise with (nigh infinite) observers that can each think of it as local Doppler effects, then the whole thing is a Doppler effect.And I suppose that isn't... wrong.  But it also has the ring of... thinking of the issue as a collection of individual trees rather than a forest, which risks missing important larger-scale aspects of the phenomenon.  For example, in my admittedly quick skimming of the paper, it looks like they seem to manage to avoid talking about objects so distant that we'd have to say their relative velocity is greater than the speed of light, which makes no sense as a physical interpretation.</blockquote>

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