A white hole is a hypothetical region of spacetime which cannot be entered from the outside, although matter and light can escape from it. In this sense, it is the reverse of a black hole, which can only be entered from the outside, from which nothing, including light, can escape. White holes appear in the theory of eternal black holes. Like black holes, white holes have properties like mass, charge, and angular momentum. They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon. The white hole's event horizon in the past becomes a black hole event horizon in the future, so any object falling towards it will eventually reach the black hole horizon.


[1] http://en.wikipedia.org/wiki/White_hole

[2] http://www.pbs.org/wgbh/nova/blogs/physics/2014/08/are-white-holes-real