Hi all, I have a layman question, if I may. As you know better than I do, all sort of conclusions have been drawn from observations of the Doppler shift in light from distant objects: from the universe expansion, to the Big Bang, to the hypothesis of dark energy. My question is, has time always ticked at the same rate since the Big Bang? And, if not, what effect would that have on the conclusions drawn from Doppler measurements. (I.e., how would a wave's frequency be affected if it came from a distant region where time was ticking differently then.) Thanks!