No, the big bang model allows for three topologies: flat, spherical or hyperbolical. A picture like this is in every cosmology textbook: https://upload.wikimed

No, the big bang model allows for three topologies: flat, spherical or hyperbolical. A picture like this is in every cosmology textbook: https://upload.wikimedia.org/wikipedia/commons/9/98/End_of_universe.jpg https://upload.wikimedia.org/wikipedia/commons/9/98/End_of_u... Which one it is depends on the density. There is a critical density at which the universe is flat, and our current best measurements basically allow for all three possibilities. It's just hard to say if something is flat or actually spherical but really, really huge.