Asked by Amanda Morgan
The idea of a white hole as the reverse of a black hole is a hypothetical one. While black holes will suck in anything from light to matter into its clutches, the white hole is theorised to be a region of space-time that cannot be entered from the outside, but from which matter and light can escape – presumably spitting out that same light and matter that got sucked into the black hole in the first place.
The idea of a black hole having an exit into another universe has caused the idea of a wormhole to be dreamt up; a passage between both black and white hole. However since the very existence of a white hole violates the second law of thermodynamics, chances of a reverse black hole are very slim.
Further to this, when a star collapses into a black hole, no wormhole is produced and even if one was formed it would be unstable and fly apart. The idea that a black hole is a portal to another world, to another dimension or even to the other side of the Universe is only really one that you’re likely to find in science fiction – these exotic, high gravity objects are really a path to death and destruction rather than anywhere fancy.
Answered by science journalist Gemma Lavender