Expressing the cosmological distances with conventional terms is very confusing. For instance, if we say that "a galaxy is a 1 billion light years away" what this is really mean? 1. If all moves stopped (moves in space and expansion) the light will travel from that galaxy (center of it) and us for 1 billion years. 2. The light traveled 1 billion years before we observed it. 3. When light was emitted from galaxy, the distance was "1 billion light years", but because expansion the light traveled a different distance/time. 4. None of above. So, I understand why cosmologist are using z for a distant object. But the value of z doesn't say anything about topology of Universe and his dynamics. What are cosmologist using to describe that aspects of Universe?