I have read from Universe by Freedman, Kaufmann that our universe is largly flat so it would mean there are edges in our universe. Our universe would be like a flat piece of paper that is continually expanding. A more realistic picture might be a diagram of Einstien's fabric of space time which is a flat sheet with spheres of planets sitting on it. But from the same source they stated that the universe does not possess an edge. I can see that a spherical universe would not possess an edge but how does a flat thing not have an edge?