What about all this wormhole stuff?
The article, "Natural Wormholes as Gravitational Lenses,"
(Physical Review, by John G. Cramer, Gregory Benford, Geoffrey A.
Landis, Matt Visser and Michael Morris)
explains one theory underlying the possible existence of exotic forms of
dark matter such as wormholes.
According to Landis, a scientist at NASA's Lewis Research Center in
Cleveland, Ohio, a wormhole is a theoretical object permitted by
Einstein's theory of general relativity, where distant regions of space
are connected by a shortcut.
"Wormholes, although allowed by the theory of relativity, are
theoretically unstable," says Landis. "However, at the time of the
formation of the universe in the big-bang, wormholes could have been
stabilized by loops of negative mass cosmic string. If so, they would
still be here, and it is worthwhile to look for them. If we find one,
the implications are enormous."