# Galaxies moving relative to other galaxies?

I've been going through "Astrophysics in a Nutshell" for a college course. I'm not asking for an answer to a problem - but the author makes an aside in a problem that confused me.

At the end of a problem regarding angular-diameter distance, he says "an object at high redshift may have been closer to us at the time of emission than an object of the same size at a lower redshift, despite the fact that the high-redshift object is currently more distant".

How is this possible, given the uniform expansion of the universe? Shouldn't everything stay at the same relative distance?

• It's possible because the universe used to be much smaller, (but expanding much faster), so all distances were smaller. – Ihle May 12 '17 at 7:37

The figure in this answer shows how large an angle an object of one kpc ($\simeq3300$ lightyears) would span. For instance, you see that the galaxies of the same physical size ~5 Gly away and ~28 Gly away would span roughly the same angle on the sky.