Or more like shape OF the universe! The only book I read anymore is The Cosmic Cocktail by Katherine Freeze, and one topic she came upon was the shape of the universe.
This topic is a very hard one to think of in your head, because its hard to imagine a universe in which we live in expanding! Yet as I showed in another blog post, Hubble himself showed that it must be expanding since galaxies are growing farther away from us!
So then what just shape are we expanding from?? Or Into??? Well there are three options we have. If the density of the universe is less than the critical mass density (found in proportion to the square of Hubble's constant then we are left with a negatively curved geometry, like a saddle. If it matches the mass found from Hubble's constant than we are left with a flat geometry like a piece of paper. But if the density is greater than the one we expect, we are left with a spherical geometry.
Flat geometry is the one Einstein preferred because is it easiest to work with a flat axis instead of a curved one. The effects of these different geometries are interesting though. For example, if the universe was spherical than there would not be enough mass (and density) so after expanding a "Big Crunch" will occur after the Big Bang and the universe will collapse on itself. The other two options are not AS sad though. The flat and hyperboloid geometries on the other hand will continue to expand forever! This will lead to a big chill since the universe will be so expansive and will never stop. I did say as.
The obvious evidence points to flat, the simple answer. It has good evidence behind it though, if the universe was spherical the "Big Crunch" would have happened extremely soon after and there would not have been enough time for the galaxies and such to form! Also a hyperboloid geometry would have led to a much faster expansion than seen a the "Big Chill" would have lead to the same result.
The numerical evidence behind flat geometry is iffy at best though, and is also very complicated, so stay tuned for next time when you can decide for yourself if our universe is like a pancake or a basketball!