Hi, I can't visualize how the universe could be infinitely flat according to the big bang theory... The only way I can visualize this is like a cone surface, one dimension supressed and left with a circle line (the universe), the other dimension thus forming the cone, is time. Now, in a fourth dimension the ends of the circle never meet, thus forming a spiral line. This universe is flat (as cones are topologically flat surfaces), infinite and isotropically expanding. I am confused. I needed 4 dimensions to represent a universe which is only a line. How many dimensions are needed for the familiar 3D universe? 5 dimensions suffice? How is it done? Please help. Or maybe expansion is accelerated. Then we have a hyperboloid-like surface. Is my thinking any valid?