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Black Holes Encyclopedia
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Fact vs. Fiction

Black holes are among the most fascinating objects in the universe, and they create phenomena that are truly bizarre. But there are limitations on a black hole's weirdness. Here are a few differences between the fact and fiction of black holes:

• A black hole's "surface" is not solid. The surface is called the event horizon, and it's essentially the point of no return for anything that approaches the black hole. It represents the distance from the black hole's singularity at which the escape velocity equals the speed of light. Anything that passes through the horizon is trapped inside the black hole. Thus, you could not crash into a black hole. Instead, you would pass right through its surface on your way to a nasty fate at the singularity.

• From a distance, a black hole's gravitational pull is no different from that of any other star or other object of the same mass. If our Sun were suddenly replaced with a black hole of the same mass, for example, there would be no change in Earth's orbit -- the planet would not be "sucked in" by the black hole. A black hole's surface gravity is stronger than that of a normal star because all of its mass has been squeezed into an almost infinitely small point. But from comparable distances in space, if you judged by gravitational pull alone, you couldn't tell the difference between a black hole and any other object of the same mass.

• Our Sun will not become a black hole because it is not massive enough. Instead, it will end its life as a white dwarf -- a hot, dense ball only about as big as Earth, but containing about two-thirds of the Sun's original mass. The remaining mass will be blown off into space.

• So far, at least, there's no evidence that black holes are portals to other places or times. Although some theoretical work suggests this possibility, no one has detected the "exits" from such portals. Some theories also suggest that a black hole's mathematical cousin, a wormhole, could serve as such a portal, but only under "imaginary" circumstances that could not really exist in the physical universe.