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Hawking's pair production


Entropy of a black hole: Jacob Bekenstein, Stephen Hawking
John Wheeler Scientist
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This business of dropping things into a black hole and having everything disappear has some ramifications that aren't immediately obvious. I thought of the Second Law of Thermodynamics, it says that everything degenerates to a uniform temperature. You put a hot tea cup next to cold tea cup and they come to a common temperature. That makes me unhappy. I have contributed to the entropy of the universe, the degree of disorganization of the universe by putting two together. But I said, when Jacob Bekenstein came in the room as a graduate student, Jacob if a black hole comes by I could drop both tea cups into the black hole and conceal the evidence of my crime." Well, he looked uncomfortable but he didn't have any positive objection then, but he came back in a few months and he said "You have not avoided the entropy increase, you've just put the entropy increase in a new place. The black hole itself is entropy." Well, it turns out that the amount of entropy a black hole has is proportional to its area, and he gave a formula which only the numerical constant was missing. But an artist who illustrated this book of mine, A Journey into Gravity and Spacetime, was working with a friend of his to make a picture, entropy proportional to the surface, and he was drawing little boxes all over the surface and he put a black or a white dot on each box, and his friend was tossing coins all the time, telling him "Okay, it's heads up. Put a black dot. Head's down, white dot." And this degree of disorder shown on the surface, it gives a pictorial representation of the entropy of a black hole. Well, you remember that when Bekenstein's paper came out the whole argument seemed so implausible to Stephen Hawking and his friend [Brandon Carter] that they decided to write a paper to prove it was wrong, and ultimately they came to the conclusion it's right, and that this nature will show itself up in another way, that a black hole is able to evaporate electrons from its surface.

John Wheeler, one of the world's most influential physicists, is best known for coining the term 'black holes', for his seminal contributions to the theories of quantum gravity and nuclear fission, as well as for his mind-stretching theories and writings on time, space and gravity.

Listeners: Ken Ford

Ken Ford took his Ph.D. at Princeton in 1953 and worked with Wheeler on a number of research projects, including research for the Hydrogen bomb. He was Professor of Physics at the University of California and Director of the American Institute of Physicists. He collaborated with John Wheeler in the writing of Wheeler's autobiography, 'Geons, Black Holes and Quantum Foam: A Life in Physics' (1998).

Tags: Stephen Hawking

Duration: 3 minutes, 42 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008