hey can radiate matter and energy. As they do this, they slowly lose mass, and thus are said to evaporate. Black holes, it turns out, follow the basic laws of thermo-dynamics. The gravitational acceleration at the event horizon corresponds to the temperature term in thermo-dynamical equations, mass corresponds to energy, and the rotational energy of a spinning black hole is similar to the work term for ordinary matter, such as gas. Black holes have a finite temperature; this temperature is inversely proportional to the mass of the hole. Hence smaller holes are hotter. The surface area of the event horizon also has significance because it is related to the entropy of the hole. Entropy, for a black hole, can be said to be the logarithm of the number of ways it could have been made. The logarithm of the number of microscopic arrangements that could give rise to the observed macroscopic state is just the standard definition of entropy. The enormous entropy of a black hole results from the lost information concerning the structural and chemical properties before it collapsed. Only three properties can remain to be observed in the black hole: mass, spin, and charge. Physicist Stephen Hawking realized that because a black hole has a finite entropy and temperature, in can be in thermal equilibrium with its surroundings, and therefore must be able to radiate. Hawking radiation, as it is known, is allowed by a quantum mechanism called virtual particles. As a consequence of the uncertainty principle, and the equivalence of matter and energy, a particle and its antiparticle can appear spontaneously, exist for a very short time, and then turn back into energy. This is happening all the time, all over the universe. It has been observed in the Lamb shift of the spectrum of the hydrogen atom. The spectrum of light is altered slightly because the tiny electric fields of the...
