[Moderator's note: post spun off from previous thread.] I'd really like some verification on the following. After thinking about light redshift, I came to the following conclusion: Is it true that λObs / λEmit for 1 particular star doesn't stay constant over time even if its recession speed is constant? The reason I'm thinking this is because, unlike doppler shift, cosmological redshift is dependent on the time for the light to travel and not only the recession speed. As the star recesses over time, light of that star would increasingly need more time to reach us and thus it would be longer and longer subject to the expansion which is continuously occurring and responsible for the redshift. λObs for that star would therefore increase over time and thus the ratio λObs / λEmit would get larger. So even is the recession speed is constant, λObs would still get larger since the expansion has more time to redshift its light because of the increasing distance from us. So, in case of a constant linear expansion rate, would this statement be true for (maybe one of the many) the above mentioned reason?