Topology of the universe

According to the general theory of relativity, spacetime is a pseudo-Riemannian manifold[?]. The topology of the universe is the underlying topology of this manifold.

We do not yet know the global topology of the universe, and in fact may never be able to know what it is. However, cosmologists are trying to measure cosmic topology using data from ground-based and space-based telescopes. Results from the WMAP telescope may give an answer by 2003 or 2004.

See also shape of the universe