Slashdot Mirror
Doughnut-Shaped Universe Back In the Race
SpaceAdmiral writes "The once-popular idea that the universe could be small and finite is making a comeback. Many researchers thought that a 'wraparound' universe would mean that distant objects would be seen multiple times in the sky, but new research suggests that a '3-torus' (or 'doughnut universe'), as well as other shapes, could fit our actual observations, particularly the WMAP data."
Ha! When I submitted it it was available for free. They must have changed it when they noticed all the /. traffic.
...Or is the idea of an edge just not valid?It isn't valid because a 3-torus is a 4 dimensional shape. To be more accurate it is valid, but not in a way you can conceive of.
Think of it in these terms; you are a two dimensional creature. Your world is defined solely by X and Y coordinates and is of a finite size. Take two opposite sides and bring them together and now your world is a tube. The only edges you can perceive are the ends of the tube. Take the two ends of the tube and bring them together. You are now living on a standard torus (not a 3-torus). As far as you are concerned there is no "edge" to the torus. Roam as much as you want to but you will never reach an edge. The only way for you to experience an "edge" would be if you stepped up one dimension and became three dimensional.
A 3-torus is a similar construct but instead of being a two dimensional world with the X edges and the Y edges brought together it is a three dimensional world in which the X edges, Y edges, and Z edges have all been brought together. From your three dimensional perspective there is no "edge" and the only way to perceive one is to step up a dimension and become a four dimensional entity.