  Noncommutative geometry, an offshoot of string theory, replaces point-like
objects by smeared objects. The resulting uncertainty may cause a black hole to
be observationally indistinguishable from a traversable wormhole, while the
latter, in turn, may become observationally indistinguishable from a gravastar.
The same noncommutative-geometry background allows the theoretical construction
of thin-shell wormholes from gravastars and may even serve as a model for dark
energy.
