# How to test whether galaxies are moving away from each other in a static background or whether space is being created beween them?

Observations show that galaxies are moving away from one another on the macroscopic scale.

Now, scientists interpret this by saying this happens not because galaxies are really moving away from each other in a static background but because more and more space is created between galaxies.

Now how scientists can distinguish between the 2 scenarios? what made them believe in the 2nd and discard the 1st?

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Some scientists interpret the expansion as space being created, but it's not a universally accepted interpretation by any means. Here's a related question, by the way. – David Z Feb 19 '12 at 19:39
@DavidZaslavsky This is the interpretation by Nima Arkani-Hamed, he stated explicitly that it is the creation of space. Those who adopt one interpretation over another must have strong reasons to discard the other one. – Revo Feb 19 '12 at 21:16
Yes, and if you're interested in looking into that, I'd suggest starting by finding out Nima Arkani-Hamed's strong reason for believing in the creation of space as opposed to motion through space. In any case, just because one prominent scientist accepts one interpretation doesn't mean that scientists in general do. – David Z Feb 19 '12 at 21:34

It's an anomaly, but if you start with the Roberrtson-Walker spacetime and make the coordinate substitution $R=ra$, replacing $r$ with $R$, it's exactly what you'll see--a static 3-geometry with a frame dragging'' effect. – Jerry Schirmer Feb 20 '12 at 13:33