So general relativity gives us some great ideas about the shape of the universe, But truly, No one can know for certain what shape the universe is until we are able to see it from the outside, But knowing the shape of the universe Can give us many insights into the nature of the cosmos itself. It all really comes down to two basic models, Does the universe have a positive curvature or a negative curvature? I mean, There is the option it has no curvature and is flat, We just don't know, But A positive curvature fits nicely in a spherical bubble like universe model, while A negative curvature more or less tells us, The universe didn't have enough mass to form a positive curvature and therefore may expand infinitely, While the closed positive curvature does fit nicely with multiverse theory, But one needs to mention in a positive curvature universe it may not expand infinitely and will eventually collapse back in on it'self. So Pros and cons to both I suppose :/ As I understand it, Knowing the shape of our universe could tell us things like, if this universe were infinite then there would be no multiverse, Because this one universe was infinite, So, negative Curvature equals an infinite universe with no possibility of a multiverse, While positive curvature equates to, A Finite universe with the possibility of others because a universe is a finite thing. I propose this theory, It's just a thought, What if the Cosmic Microwave background isn't an end, But a horizon the hides a curvature.