Science is awesome update 3
What shape is the universe? We don't know. It could be cylindrical or even doughnut shaped. However, the 'shape' or geometry of the universe is determined by its density, as density governs the relationship between momentum of expansion and the inward pull of gravity. If the density exceeds a critical value, the universe is round. If it is lower than the critical value, it is open (infinite) and curved like a saddle. If it exactly matches the critical value, then it is flat. By measuring ripples in the cosmic microwave background, NASAs WMAP mission has recently revealed that the universe is flat with a 0.4% margin of error.