• Question: is the universe infinite or dose it end

    Asked by anon-265126 on 15 Oct 2020.
    • Photo: James Smallcombe

      James Smallcombe answered on 15 Oct 2020:

      That’s a good question we are still trying to answer.
      Hopefully a better cosmologist than me that can explain more.
      As I understand the universe is still expanding from the big bang, but has a finite size.
      We don’t know for sure if it will keep getting bigger or eventually start shrinking.

      Of course when someone says the universe is finite, not infinite, then people might ask about the “edge” and what’s beyond. And I really dont have a good answer.

    • Photo: Richard Fielder

      Richard Fielder answered on 16 Oct 2020:

      We’re not actually entirely sure. In the past, it was assumed that the universe must be finite, since it started with the Big Bang and has only had a finite time in which to expand. But more recently there is a theory called inflation that does a very good job explaining how matter is distributed around the universe, but says that much more rapid expansion very early in the universe’s life could actually have resulted in it being infinite.

      The tricky part is that we can’t actually see most of it. Since light has a limited velocity and the universe has a finite age, there has only been time for light to travel a certain distance. Anything further away than that we can’t see. So we know for sure that the universe is at least 90 billion light years across, and we can infer that it must be quite a bit bigger since otherwise the things right at the edge of where we can see would behave differently. But since we can’t observe anything further away, it’s very difficult to test any theories on the matter.

      This is even more complicated by the expansion of the universe, which seems to be accelerating. That means that things near the edge of the observable universe are actually moving away from us faster than light (which is possible because it’s the space between them expanding, not their own movement within that space). That means not only we will never be able to see anything beyond the current limits, things we can currently see will start to move past the limit and become invisible.

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