0
$\begingroup$

This question already has an answer here:

From Earth we say that the age of the universe is 14.5 billion years ago because that is how far we are able to see. But since we are probably not the center of the universe, wouldn't some one many billion light years away from us feel that the age of the universe is different ?

If so, how is it possible that the age of the universe varies by distance ?

This question came to my mind whilst watching tis video https://www.youtube.com/watch?v=mGBm5Ywjd5o [about the 8:30 mark till 12 mins]

$\endgroup$

marked as duplicate by John Rennie, JamalS, Jim, Martin, ACuriousMind Feb 23 '15 at 21:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ That is not the reason we say it's 14.5 billion years old. The age is the same everywhere. $\endgroup$ – lemon Feb 23 '15 at 13:07
  • $\begingroup$ What is the actual reason? $\endgroup$ – Chani Feb 23 '15 at 13:09
  • $\begingroup$ "Since we are probably not the center of the universe..." Actually, because the universe is infinite (as far as we can tell) it is meaningless to designate a center of the universe. $\endgroup$ – Sean Feb 23 '15 at 13:10
  • $\begingroup$ @sean I thought we say the universe is infinite because it appears so from our point of view ie we haven't seen the end of the universe - however are there any theories that say the universe has to be infinite? And if one says that the universe is actually infinite, doesn't the concept of expanding universe become a little hard to digest? What does an already infinite expanding entity expand into? $\endgroup$ – Chani Feb 23 '15 at 13:14
  • $\begingroup$ An expanding Universe doesn't need anything to expand into, no matter if it's finite or infinite. The reason we think its infinite is that its (in)finiteness is connected to its average density <ρ>; if <ρ> is above a certain threshold, then its "only" finite. However, observationally it is found that to a high precision, <ρ> is exactly equal to the critical value. Also, even a finite universe doesn't have a center, just as the finite 2D surface area of a ball doesn't have one. If the surface were populated by ants, they could all (rightfully) claim to be at the center. $\endgroup$ – pela Feb 23 '15 at 15:34
1
$\begingroup$

The question does not depend on the distance but on other factors subject to time dilation, that is movement and gravity: In short, time is passing slower for a bus driver on Jupiter than for a prisoner on Mars.

The time between the beginning of the universe and today is measured by mass particles, each mass particle may be considered as a clock. The age of the universe for massless particles such as photons would be zero because they do not experience any proper time, their clock would always be at zero. Rapid particles moving near light speed which survived since the beginning of the universe are measuring an age of the universe which is much smaller than our measurement.

Searching for an objective measurement of the age of the universe we can use space expansion which is time dependent, by referring to a reference frame which is comoving with space expansion. Earth is moving with non-relativistic velocity with respect to this comoving frame, and as a result we can consider that our clocks are (nearly) in tune with this kind of objective measurement of the age of the universe.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.