See video too.Mar 27, 2015 by Fraser Cain, Universe Today
Two possibilities exist: either the Universe is finite and has a size, or it's infinite and goes on forever. Both possibilities have mind-bending implications.
In another episode of Guide to Space, we talked: "how big is our Universe". Then I said it all depends on whether the Universe is finite or infinite. I mumbled, did some hand waving, glossed over the mind-bending implications of both possibilities and moved on to whatever snarky sci-cult reference was next because I'm a bad host. I acted like nothing happened and immediately got off the elevator.
So, in the spirit of he who smelled it, dealt it. I'm back to shed my cone of shame and talk big universe. And if the Universe is finite, well, it's finite. You could measure its size with a really long ruler. You could also follow up statements like that with all kinds of crass shenanigans. Sure, it might wrap back on itself in a mindbending shape, like a of monster donut or nerdecahedron, but if our Universe is infinite, all bets are off. It just goes on forever and ever and ever in all directions. And my brain has already begun to melt in anticipation of discussing the implications of an infinite Universe.
Haven't astronomers tried to figure this out? Of course they have, you fragile mortal meat man/woman! They've obsessed over it, and ordered up some of the most powerful sensitive space satellites ever built to answer this question.Astronomers have looked deep at the Cosmic Microwave Background Radiation, the afterglow of the Big Bang. So, how would you test this idea just by watching the sky?
Here's how smart they are. They've searched for evidence that features on one side of the sky are connected to features on the other side of the sky, sort of like how the sides of a Risk map connect to each other, or there's wraparound on the PacMan board. And so far, there's no evidence they're connected.
In our hu-man words, this means 13.8 billion light-years in all directions, the Universe doesn't repeat. Light has been travelling towards us for 13.8 billion years this way, and 13.8 billion years that way, and 13.8 billion years that way; and that's just when the light left those regions. The expansion of the Universe has carried them from 47.5 billion light years away. Based on this, our Universe is 93 billion light-years across. That's an "at least" figure. It could be 100 billion light-years, or it could be a trillion light-years. We don't know. Possibly, we can't know. And it just might be infinite.
Read more at: http://phys.org/news/2015-03-universe-finite-infinite.html#jCp