The definitions of black holes are sometimes controversial. In theory, a black hole is an area of highly concentrated mass. So concentrated, that no object can escape its gravitational pull. In other words, once you get caught by its gravitational pull, it is impossible to get out. The velocity required to escape from the gravitational pull is called the "escape

Hollywood has a big effect on the way we view astronomy, and one of the more recent anomalies taken over by Hollywood is the possibility of the "wormhole". Before you can understand what a wormhole is, you need to understand what a "white hole" is. The opposite of the mathematical equation for the black hole has been proven valid. The name for this opposite of a black hole is in fact, a white hole. A white hole is the exact opposite of a black hole. As black hole sucks stuff in, a white hole spits stuff out. Although in a mathematical sense is fine, the possibility of its existence in space is unlikely. Since a white hole is a time reversal of a black hole, creating one is impossible (as destroying a black hole is impossible). But because the universe's possibilities are endless, we cannot discard the possibility of the white hole. Now, the wormhole is thought to be a "link" between a white hole and a black hole, as the black hole sucks stuff in, the white hole spits it right out. Because space and time are not important in a black hole, the link up can go across different regions of space-time, or even different galaxies or universes. If a wormhole did exist, it is considered that its stability would be very limited, as even the slightest perturbation of it would cause it to collapse. If you could find a stable wormhole, travelling through it would be deadly, as radiation from nearby stars would fry you to death.

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