Question: Is the universe infinite?

Kevin Healy answered on 17 Nov 2014:

Thats a good question and in short we dont know. Because the speed of light is not infinite (although it is very fast travaling 299792458 meters every second) but is the fastest thing in the universe, we can only see 13.7 billion light years away. This is what is called the visable universe which is certainly not infinite. However even if we consider the visable universe it might one day be infinite. We know the universe started with the big bang but we dont know how will it end. If gravity is strong enough one way it will end is in a big crunch with everything being dragged back together. However if there is not enough gravity to do this the universe might simply get bigger and bigger with nothing to stop it. This would mean time is infinte and so eventually after an infinte amount of time the universe would be of an infinite size.
But what about now and the universe outside the visable universe, is that infinite? This is very hard to answer but one way to do that is to look at the shape of the universe. If the univese is flat like a table then its would be in a sense inifinite with no edges. However if the universe was shaped like a donut then it would look flat (It would be flat in a mathematical sense) however it would’nt be infinite as you could travel around and end up in the same place just like if you traveled around the world to get back to the same place. There is currently a satelite called Planck that will measure the background looking for patterns that tell us if the universe is either like a table or donut so maybe we might know sooner then we expect!