Question: Do you think that the universe ends somewhere? It seems impossible that it continues on forever, so what is your theory on it?

Michaela Livingstone answered on 17 Jun 2010:

Well, I agree, the way we experience ‘reality’, what makes sense to us, yeah it would make sense that there HAS to be a boundary somewhere, ie the universe stops somewhere. We can only ‘see’ as far away as light has travelled since the big bang, and also that is bright enough ot have reached our teloscopes over vast distances, so maybe even if we can only ‘see’ so far, that doesn’t rule out there being anything past that point. In my mind, if everything in the universe starting expanding at the big bag and expanded at the speed of light, then the universe will be as far as that stuff could travel in the 15.7 billion years that has passed since the big bang. So about 92294491000000000000000 miles from end to end. (I can’t figure out a good way to explain how big that is… you could travel to the sun and back tens of billions and billions and billions of times in that distance…)

Having said this some physicists say that spacetime – the fabric that makes up our universe, is shaped like a doughnut, and that you can’t pass out through it, instead only along – this means you’d eventually end up back where you started. Really hard to explain. Marcus DuSatoy, a mathmatician, did a TV program on this a while back but I can’t find it anywhere, sorry.

A couple of physicists reckon that we’re just projections (holograms) of things that are actually happening at the boundary of the universe, so that would mean the edge of it is somewhere…

Having said that, yet more physicists say that the universe is a flat sheet floating about in a mega-universe with other universes. These could all just be random things that come out of maths that theoretical physicists use and don’t actually represent reality, so I’d go with what we have the best evidence of, and that’s a spherical universe, so shaped like a football.