OK, let's imagine that in a few billion years time, when our local group of galaxies have merged, our Sun has reached and surpassed it's giant red phase stage and has become a White Dwarf, and we as a species are extinct. At the same time the distant galaxies will have moved beyond our observable universe. Let's say that around this time another species has evolved and reached a stage of intelligence compared to our own. They will not have any evidence of any recessional velocity of these distant galaxies, as they have moved beyond the observable horizon. Also the CMBR will be much lower, possibly undetectable.....So how would such a species reach a conclusion that we were living in a dynamical expanding universe? Would cosmology knowledge be curtailed for them by these distant events?