In a flat universe, all of the local curvature and local geometry is flat. It is generally assumed that it is described by a Euclidean space, although there are some spatial geometries that are flat and bounded in one or more directions (like the surface of a cylinder, for example).
The alternative two-dimensional spaces with a Euclidean metric are the cylinder and the Möbius strip, which are bounded in one direction but not the other, and the torus and Klein bottle, which are compact.
In three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. The most familiar is the 3-Torus. See the doughnut theory of the universe.
In the absence of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching some fixed rate. With dark energy, the expansion rate of the universe initially slows down, due to the effect of gravity, but eventually increases. The ultimate fate of the universe is the same as that of an open universe.
A flat universe can have zero total energy. Thus, physicists suggest a flat universe could come from nothing.
Originally posted by karen61057
Its universe shaped.
Space itself is not flat, but curved. The curvature of space is responsible for gravity, and at a black hole space and time are so curved they get knotted up.
Everything in the universe - light, subatomic particles, pizzas, yourself - is described in terms of a geometrical structure on the space-time 4-manifold. Manifolds are used to understand the large-scale structure of the Universe in cosmology, and the theory of relativity introduced the idea of matter-energy equivalence, which led to nuclear power, and the atomic bomb.
The universe is now considered to be a 12 dimensional nested manifold.
In "superstring" physics, the torus is known as the "perfect" shape.
It is now accepted as a mathematical model that can be used to describe objects in space.
Surface topology is superior to geometry for describing such phenomenon because it deals with much more sophisticated and profound spacial and temporal relationships.
Other scientists have also suggested that the entire universe may be shaped like a torus.edit on 26-9-2012 by newcovenant because: harmonicresolution.com...