Can the Universe be its own mother? This figure shows how a Universe creates itself and baby universes. Four inflating baby universes are shown — A, B, C, and D — from left to right. Universe A and D have not created any baby universes so far. Universe C has created universe D. Universe B has created three universes: universe A, universe C and itself. The toroidal - shaped region at the bottom is a region of closed timelike curves which features how the Universe creates itself. The region is bounded to the future by a Cauchy horizon, after which, there are no closed timelike curves. Universes A, C, and D, for example, are formed after the Cauchy horizon when the epoch of closed timelike curves is already over.
This provides a picture for the creation of the Universe without appealing to the unknown theory of quantum gravity. The key requirement for this model is that closed time like curves are allowed to exist — which is true in Einstein's theory of general relativity. A prediction of this model is that a time arrow exists after the Cauchy horizon, which is just what we have observed daily. [For details see J. R. Gott and L.-X. Li, Phys. Rev. D 58, 023501 (1998); L.-X. Li and J. R. Gott, Phys. Rev. Lett. 80, 2980 (1998).]