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According to Wikipedia:

Comoving distance factors out the expansion of the universe, giving a distance that does not change in time due to the expansion of space (though this may change due to other, local factors such as the motion of a galaxy within a cluster)

Who was the person who came up with the idea of comoving distance?

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  • $\begingroup$ Did you check to see whether the first guys publishing on FLRW universes didn't already use it? It seems like a very obvious concept. $\endgroup$
    – Danu
    Jul 20 '15 at 20:21
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From Longair's Cosmic Century it appears that Milne and McCrea introduced comoving radial distance in 1934 in their analysis of Friedmann–Lemaître–Robertson–Walker expanding universe solutions to general relativity.

"They showed that despite the fact that Newtonian mechanics can not provide a fully consistent cosmological model, simple ideas from Newtonian physics can provide insight into solutions". Using Newtonian gravity they "derived formulae of exactly the same form as in full theory" with comoving distance to a galaxy as a coordinate. "Not unexpectedly the Newtonian argument can not cope with the curvature of space, and a relativistic expression for the inertial mass density is needed, which includes the pressure of the gas... The analysis of Milne and McCrea was important because it showed that, despite the problems with boundary conditions at infinity the Newtonian model can be used successfully on large scales in the Universe...".

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