View Single Post
SpaceTiger is offline
Jan12-06, 03:16 AM
Sci Advisor
PF Gold
SpaceTiger's Avatar
P: 2,977
Quote Quote by Blahness
Since stars further away are seen moving faster then stars closer, and those stars are seen as younger, does that mean that as time passes, the expansion slows, answering the question of what's happening to the universe?
I'll assume you're talking about cosmological scales, on which we observe galaxies and quasars instead of individual stars. It turns out that more distant objects would appear to be moving more quickly (and appear younger) regardless of whether the universe were accelerating or decelerating.

Think of it this way. The apparent speed of the receding galaxies is measured by the redshift of their light. The amount that light becomes redshifted is related to the amount by which the universe has expanded during its journey to us. Light coming from more distant objects will always have to travel further to reach us, so the universe will always have expanded more during its trip. Thus, light from more distant objects will always appear more redshifted and we'll always infer their recession velocities to be higher, as long as the universe is expanding. If the universe were contracting, then the opposite would be the case.