Like part of a cosmic Russian doll, our universe may be nested inside a black hole that is itself part of a larger universe.

In turn, all the black holes found so far in our universe - from the microscopic to the supermassive - may be doorways into alternative realities.

According to a mind-bending new theory, a black hole is actually a tunnel between universes - a type of wormhole.  The matter the black hole attracts doesn't collapse into a single point, as has been predicted, but rather gushes out a "white hole" at the other end of the black one, the theory goes.

In a recent paper published in the Journal Physics Letters B, Indiana University physicist Nicodem Poplawski presents new mathematical models of the spiralling motion of matter falling into a black hole.  His equations suggest such wormholes are viable alternatives to the "space-time-singularities that Albert Einstein predicted to be at the centres of black holes."
(extract via by Ken Than    http://news.nationalgeographic.com  published April 9, 2010)