• Question: Is the universe infinite? Because if it isn\'t, what could be outside it? I don\'t understand how something can just stop - doesn\'t there have to be something around it?

    Asked by annabel to Paul on 23 Mar 2010 in Categories: .
    • Photo: Paul Stevenson

      Paul Stevenson answered on 23 Mar 2010:

      Hi Annabel,

      It’s difficult to answer this question talking about three-dimensional space, but imagine were only aware of two-dimension and lived on the surface of a sphere (like the earth). We would be living on a finite-sized space, because the surface of Earth does not go on for ever, but we would be able to go on traveling for ever. Space could be like this too – it could have a finite size, but could loop back on itself. It’s pretty much impossible to visualise it, because we would need to imagine a fourth spatial dimension, just like a sphere exists in three dimensions, but it’s possible.

      Does that help? Please feel free to follow up with a comment and I will do my best to answer

      Paul

Comments

  • modshamini commented on :

    So like if you walked in a straight line on the earth, you would eventually come back to where you started, you could do that in space too? So you’d be flying your spaceship and then suddenly end up at the same place again!
    When you say a fourth spatial dimension, do some people not call ‘time’ the fourth dimension?