A black hole is an extremely dense point in the universe, through which nothing, not even light, can pass (hence the name "black" hole). Black holes are sometimes created when a star implodes in a supernova. They are so dense that anything to come in contact with one's "event horizon", the boundary of a black hole in which nothing can escape, would be sucked in.
A black hole is shaped like a conical cylinder, tapering to a point, called its singularity. At this point of singularity, gravity is so strong that the laws of physics do not exist and all matter is crushed, sometimes called "spaghettification". There are in theory two kinds of black holes. The first is a non-rotating black hole, or a Schwarzschild black hole, named after German astronomer Karl Schwarzschild, who conceived it.
However, there is also another kind of black hole, and this is the rotating kind! Called the Kerr hole, this theoretical black hole could be used as a portal for travel between the time of to parallel universes. In Roy Kerr's theory, stars would collapse into a ring of rotating neutrons. This means that a centrifugal force would be created and hypothetically be enough to prevent the singularity from forming. Because of the lack of singularity, Kerr thought that it would be possible to enter safely without being crushed by gravity. At the end, you would emerge through a "white" hole, the end of the passage to another world so to speak.
Another theory that utilizes black holes for time travel, is that one that plays with the idea of getting a spaceship going at almost the speed of light, and going around the edge of the black hole. Due to time dilation and the large gravitational pull, the people on the ship would experience time half as fast as those not on it. So, they would be at a different point in time than those on Earth, and therefore be time traveling.
A black hole is shaped like a conical cylinder, tapering to a point, called its singularity. At this point of singularity, gravity is so strong that the laws of physics do not exist and all matter is crushed, sometimes called "spaghettification". There are in theory two kinds of black holes. The first is a non-rotating black hole, or a Schwarzschild black hole, named after German astronomer Karl Schwarzschild, who conceived it.
However, there is also another kind of black hole, and this is the rotating kind! Called the Kerr hole, this theoretical black hole could be used as a portal for travel between the time of to parallel universes. In Roy Kerr's theory, stars would collapse into a ring of rotating neutrons. This means that a centrifugal force would be created and hypothetically be enough to prevent the singularity from forming. Because of the lack of singularity, Kerr thought that it would be possible to enter safely without being crushed by gravity. At the end, you would emerge through a "white" hole, the end of the passage to another world so to speak.
Another theory that utilizes black holes for time travel, is that one that plays with the idea of getting a spaceship going at almost the speed of light, and going around the edge of the black hole. Due to time dilation and the large gravitational pull, the people on the ship would experience time half as fast as those not on it. So, they would be at a different point in time than those on Earth, and therefore be time traveling.