Another Country Heard From
Perhaps 30 years ago, I read in a book by Freeman Dyson the theory that the other side of a black hole is a white hole, spewing matter and/or energy into another location, perhaps another universe. It has been posited that in another universe, the big bang would appear to be a white hole.
"The concept of a “white hole,” a hypothetical object emerging spontaneously from a singularity – or a time-reversed version of a black hole – was introduced by Igor Novikov in 1964, but without referring to it as a white hole. The following year the concept was independently considered by Yuval Ne’eman, who called the object a “lagging core.” The apt name “white hole,” which may first have been used in 1971, soon became popular while “lagging core” was forgotten. Contrary to the black holes, white holes or lagging cores are not believed to exist in nature. They were sometimes called “little bangs,” a term also used with somewhat different connotations (Hoyle 1965; Harrison 1968).'
—http://arxiv.org/ftp/arxiv/papers/1301/1301.0219.pdf