# Hawking's Equation

awking has written down an equation which looks rather like Planck's equation. Hawking's equation is S = kA, where S is the entropy of a black hole, A is the area of its surface, and k is a constant which I call Hawking's constant. Entropy means roughly the same thing as the heat capacity of an object. It is measured in units of calories per degree. A is measured in square centimeters. Hawking's equation says that entropy is really the same thing as area. The exchange rate between area and entropy is given by Hawking's constant, which is roughly 10^41 calories per degree per square centimeter. This factor of 1041 shows how remote a black hole is from humanly comprehensible and familiar units. But what does it really mean to say that entropy and area are the same thing? We are as far away from understanding this now as Planck was from understanding quantum mechanics in 1900. All that we can say for certain is that Hawking's equation is a clue to the riddle of black holes. Somehow, we can be sure, this equation will emerge as a central feature of the still unborn theory which will tie together gravitation and quantum mechanics and thermodynamics.

## Notes:

Folksonomies: physics equation

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Concepts:
Energy (0.950306): dbpedia | freebase
Entropy (0.904966): dbpedia | freebase
Physics (0.899662): dbpedia | freebase | opencyc
Thermodynamics (0.871574): dbpedia | freebase
Quantum gravity (0.867527): dbpedia | freebase
Stephen Hawking (0.839954): dbpedia | freebase | opencyc | yago
Black hole (0.829174): dbpedia | freebase | opencyc
General relativity (0.722358): dbpedia | freebase | opencyc  Infinite in All Directions
Books, Brochures, and Chapters>Book:  Dyson , Freeman J. (2004-07-22), Infinite in All Directions, Harper Perennial, Retrieved on 2012-04-25