(Caption) Does a spinning massive object wind up spacetime? Credit: J Bergeron / Sky and Telescope Magazine. An APOD for 7 November 1997.
It has been reported that a recent scientific paper delivers the conclusion that our universe resides inside a black hole in another universe – which is not exactly what was concluded. Also, that work delivers some more interesting, or at least more tangible, ideas about how our early universe may have unfolded.
The Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity – claimed as an alternative to general relativity theory, although still based on Einstein field equations – seeks to take greater account of the effect of the spin of massive particles. Essentially, while general relativity has it that matter determines how spacetime curves, ECKS also tries to capture the torsion of spacetime, which is a more dynamic idea of curvature – where you have to think in terms of twisting and contortion, rather than just curvature.

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But the new baby universe can’t be born and expand in the black hole. Remember this is general relativity. From any frame of reference outside the black hole, the events just described cannot happen. Clocks seem to slow to a standstill as they approach a black hole’s event horizon. It makes no sense for an external observer to suggest that a sequence of events is taking place over time inside a black hole. If it remained in our universe, the potential baby universe would have no time to play with before the black hole evaporated – even though from an external frame of reference that might be a googol years later.

Instead, it is proposed that the birth and expansion of new baby universe proceeds along a separate branch of spacetime via the black hole acting as an Einstein-Rosen bridge (i.e. a wormhole).




(Caption) The horizon problem in Big Bang cosmology. How is it that distant parts of the universe possess such similar physical properties? Well (putting your Occam brand razor aside), perhaps the whole contents of this universe was originally homogenized within a black hole from a parallel universe. Credit: Addison Wesley.


If correct, it’s a turtles on turtles solution and we are left to ponder the mystery of the origin of the multiverse – or at least the primeval universe which first formed black holes from which all subsequent universes originate.

What’s just as interesting about ECKS is that the torsion concept provides an alternative explanation to cosmic inflation. Matter and energy crunched within a black hole should achieve a state of isotropy and homogeneity (i.e. no wrinkles) – and when it expands into its hypothetical wormhole, it does so via the unwinding of the spacetime torsion that was built up in the black hole. So you have an explanation for why a universe expands – and why it’s so isotropic and homogenous.

Further reading: Poplawski, N.J. (2010) Cosmology with torsion – an alternative to cosmic inflation.
http://arxiv.org/abs/1007.0587