Is it defined in any way? Is there any limit to how far it spans or does it go on forever? (And can you explain it so a layman can understand?) Just pondering…
What exactly is the universe, google search: http://people.ucsc.edu/~cluine/overview%20of%20universe.html
What is the universe? It is everything.
Frankly speaking, we don’t know!
But right now there are three main theories abt what is the limits and spans of the universe.
- “Open universe” The universe will continue expanding for ever and ever at the current rate.
- “Flat universe” The universe expands without end but expansion gradually slows.
- “Closed universe” The universe will collapse upon itself eventually.
Which theory is the correct one or even if any will have to depend on what is the real total mass of the universe, which we don’t have a clue.
How far does it span? I don’t know this for sure but if we assume the Universe is 15 billion years old (give or take a few billion years) then the Universe should be 30 billion light years in diameter (assuming it is spherical and discounting inflation theory).
However, as far as you and I are concerned it goes on forever. Even travelling at near lightspeed you’d never get to the ‘edge’ (loosely speaking as there is no edge).
Finally, I’m think scientists are pretty sure today, given some good measurments taken in the past several years, that the universe is Flat (#2 in Nishroch Order’s list). I had always hoped for #3 as the other two suggest a bleak, dismal end to the universe but I wasn’t consulted in the creation of the universe.