Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

A comment to my question straightens out a misconception.

That places the furthest theoretically observable edge of universe at 13.798 bln light years away - this is how long light would take to reach us from there, and there were no light sources before that date.


"That places the furthest theoretically observable edge of universe at 13.798 bln light years away" Makes sense in a naive way, but not so. Part of the travel occurred when space was smaller than it is now. – dmckee♦

Well, let me ask, by how much was I off?

How far is currently the point of universe, radiation/light from which, originating in the early times of the universe (say, 150mln years after big bang, when great inflation had long ended and first stars formed, and the speed of expansion got mostly constant) would reach Earth today? How much distance over Hubble length could have light covered over Hubble time thanks to space expansion?

share|cite|improve this question
up vote 2 down vote accepted

The furthest we could possibly see using light waves is the so called surface of last scattering (because before this time the universe was opaque). This is the distance that the cosmic microwave background appears to be coming from, and it is currently about 46.6 billion light years away. See the Wikipedia article on the observable universe for more details.

share|cite|improve this answer
I strongly recommend if you want to know more about this sort of thing. – John Rennie Oct 24 '13 at 17:54

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

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