If you look farther and farther away, you also look farther and farther into the past. The earlier you go, the hotter and denser, as well as less-evolved, the Universe turns out to be. The part that we can see is limited and finite. But what about what lies beyond? Image credit: NASA / STScI / A. Feild (STScI).

Ask Ethan: Is the Universe infinite or finite?

Either possibility offers a tremendous existence, but philosophically, there’s so much more to think about.

“If the doors of perception were cleansed every thing would appear to man as it is, Infinite. For man has closed himself up, till he sees all things thro’ narrow chinks of his cavern.” -William Blake

13.8 billion years ago, what we know as our Universe began with the hot Big Bang. It’s been expanding and cooling ever since, up through and including the present day. From our point-of-view, we can look back some 46 billion light years in all directions, thanks to the speed of light and the expansion of space. Although that’s a huge distance, it’s not infinitely large. But that’s merely what we can see. What lies beyond that, and could that be infinite? That’s what Buck wants to know, as he asks:

What I’d like to see discussed whether the universe is finite or infinite, and why it might be either. I’ve seen some limited discussion by [Sean Carroll] and [Lisa] Randall to the effect it could be either. We just don’t know.

It’s true that we don’t know whether it’s finite or infinite, but we know a lot more than what we see within the part that’s observable to us.