What shape is our universe?

Could our universe be flat?
22 November 2022



Now we can see back almost to the beginning of the universe, we can see a long way in each direction. So what shape is the universe that we see?


Rosemary - Oh, this is a tricky question. So this is addressing a part in astronomy that is the observable universe versus the universe itself. So the observable universe being, when you look up at the night sky, when telescopes are looking at the night sky, what they can see, the amount of light that they're getting in from all different directions. And we know that that is a sphere because when we look up around us, we can see stuff in all directions. Now, the universe as a whole, there's three different possibilities for what it could be. It could either be a sphere, it could be kind of a saddle shape, or it could be flat. The sphere is a positive curvature in every direction, a saddle shape being this negative curvature, and then flat, obviously being no curvature. And I believe this is taken from measurements, from the cosmic microwave background, which is so rich in information. That's why studying the cosmic microwave background is so important in astronomy because it gives us so much information about the universe and how we started and the composition of our universe, how much dark matter there is, how much matter there is. And it is one measurement where I believe if it is one, it is that the universe is flat. If it's above one, it's curved. And if it's below one, it means that our universe is kind of negatively curved, this saddle shape. And the current measurements are around this one value. And we haven't gotten it exactly precisely, which is exactly why it's important for us to keep studying the cosmic microwave background. But it's hovering around one, which means that it makes me very uncomfortable to say, but that the universe is kind of flat, which I don't like at all. I want it to be like a sphere. But that's kind of what the science is saying right now. But continuing to study this is very important and it'll give us a great understanding of the universe beyond our observable Universe.

Chris - You obviously like the idea that you can start and go on forever, come back where you started eventually.

Rosemary - Yes, I do.

Chris - Very comforting for you.


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