• Question: If the universe is only 13.8 billion years old why is it 93 billion light years in diameter? If this is true then how did the edge of the universe travel faster than the speed of light?

    Asked by Jamie W. on 26 Nov 2020.
    • Photo: Marcello Valente

      Marcello Valente answered on 26 Nov 2020:

      Dear Jamie,
      I am not an expert in this field but, from what I understand, the few moment after the Big Bang the laws of Phisics weren’t exactly the same as for now and the very event covered a large portion of space.

    • Photo: Duncan Wallace

      Duncan Wallace answered on 26 Nov 2020:

      I would have to look this up to be certain, but I believe that we can observe that things are “traveling faster than light” because of the effects of Dark Energy. This isn’t really so much the things themselves travelling faster than light (which according to our understanding of physics is impossible), but rather the amount of distance between them and us is increasing faster than one might expect. This feels like a silly distinction, but it’s important. Imagine you were in the ocean and there was a motor boat moving 10 km per hour away from you. You might find that in an hour it was 17 km away from you because the tide was pushing you backwards! Now in this case there is technically no more ocean than there was before (it was just pushing you backwards) but with space we seem to be observing that space *itself* is stretching and expanding. This has such a profound effect that it means that most galaxies will never be reachable by humans, as the space between them and the Milky Way will be increasing faster than any vessel could ever travel across it, even if traveling at the speed of light.

    • Photo: Danny Hnatyshin

      Danny Hnatyshin answered on 26 Nov 2020:

      Yes its kind of a weird fact! Here is my attempt at explaining it!
      We assume that at the big bang everything was at the same location and now we can now see points that are now 93 billion light years across. So yes in only 13.8 billion years they got 93 billion away. So even if they moved at the speed of light they shouldn’t be that far apart. The answer to the observation is that new physical space is created between objects over time (look up dark energy and cosmic inflation for technical info!). This is a really weird property of the universe, if you start with 2 stars (or apples, or people) that don’t move away from each other in the normal sense of the word and you just let them sit there new space will be created between them making the get farther apart.
      On a different not, space itself can move faster that light, its just objects within space that can’t go faster than light. Craziness!