Another Universe Might Lurk Only Millimeters Away

Another universe might lurk only millimeters away from our universe, but we wouldn't know it because it exists on its own membrane separated from our membrane in some extra spatial dimension. Matter on the other membrane would be invisible but could exert a gravitational effect and would, in fact, constitute the "dark matter" for which astrophysicists have sought for some years.

In a recent paper Paul Steinhardt (Princeton) and Neil Turok (Cambridge) propose that the structure in our universe may well have come about in the collision of two such membrane universes. All the historical events in the life of our cosmos--initial big bang, subsequent expansion of galaxies, even the currently observed accelerated expansion phase, and finally a contraction into a "big crunch"--would be played out in a recurring drama.

This cyclic cosmology (an extension of Steinhardt's "ekpyrosis" theory; see Update 535) uses all the latest tools of string theory, accounts for the "dark energy" supposedly firing cosmic acceleration, and would have no need for an ad-hoc "inflationary" phase appended to the standard big bang model to explain such cosmological features such as the horizon problem (why the extreme edges of the visible universe seem to be at the same temperature). (Sciencexpress, 25 April, soon to be in Science.)