Are black holes 'doorways' to other parts of the universe?
So far, only in science fiction. Anything that falls into a black hole is trapped there, and it cannot come out of a "white hole" elsewhere in the universe. Theory does allow the existence of wormholes, which are theoretical "shortcuts" between two points in space-time. No wormholes have been detected, though. And the theories say that as soon as any matter tried to enter the wormhole, it would collapse. Unlike the heroes of the Stargate universe we can't create our own wormholes to other planets. Artificial wormholes would require enormous amounts of a form of energy that can exist only on paper or TV screens -- not in the real universe.
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