Chapter Seven took all of what I had learned in chapter six and turned it around. Hawking describes a black hole by stating that "the boundary of the black hole, the 'event horizon', is formed by the light rays that just fail to escape from the black hole, hovering just on the edge." The light must run parallel, or away from each other, though. If they were to run toward each other, the light would collide and fall into the black hole, leaving no event horizon.
Hawking reflects on the second law of thermodynamics. It states that the entropy of an isolated system always increases. When to systems are joined together, the entropy of the combined system is greater than the sum of the entropies of the individual systems. Everything checks out when using the second law of thermodynamics, except for one thing. In order to have entropy, a body must have temperature. And to have temperature, the body must emit radiation. Therefore, black holes are supposed to emit radiation. There very definition, however, states that they are objects that do not emit anything. The event horizon of a black hole, apparently, could not be used to measure its entropy.
It turns out, however, that a rotating black hole can emit radiation/particles. But how? By using quantum theory, the particles do not come from within the black hole, but from the empty space outside the black hole's event horizon.
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