• Question: How does the universe keep expanding because it has to expand into another space , so there must be another thing out there right ?

    Asked by anon-257946 on 25 Jun 2020.
    • Photo: Julian Onions

      Julian Onions answered on 25 Jun 2020:

      No – as far as we know there is nothing outside our universe, although we can’t actually see to the edge, only to the horizon of it. It is really hard to wrap you head around, as we don’t really have any good way of thinking about it, but a balloon being blown up, and an ant standing on it might be a good way to think of it. The surface of the balloon keeps growing, so there is more and more balloon for it to walk on. Of course us standing outside watching see it expand into the room, but that is where the analogy doesn’t really work!

    • Photo: John Davies

      John Davies answered on 25 Jun 2020:

      I’m as asteroid astronomer. If I cannot land on it, and it cannot land on me, then its not really my field. However what I understand is that both space and time themselves are expanding. They are not expanding into anything. However, I should say that when I was younger, this was exactly the question I asked my Dad. So yes its a hard thing to get your head around, which is why I do asteroids!

    • Photo: Anne Green

      Anne Green answered on 25 Jun 2020:

      The Universe isn’t expanding into space, it’s space itself which is expanding.

    • Photo: Susan Cartwright

      Susan Cartwright answered on 29 Jun 2020:

      This is one of those cases where the human mind is just not equipped to visualise the situation. If we believe the standard Big Bang model, there is nothing outside of the universe (and, indeed, the universe is infinitely large, so how could there be anything outside it?). But space itself expands, so the distances between apparently fixed reference points like galaxies keep increasing (the galaxies themselves are at rest relativet to their local space).

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