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?