A Brief History of Time Nobel Prizewinner Bill Phillips (#265)
Into the Impossible With Brian Keating
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The Energy of a Photon Is Equal to Planck's Constant
We want to pick a constant of nature, a fundamental constant of nature to define the kilogram. And what we want to do is to use this same beautiful definition whereby we defined the meter by defining the speed of light. Well, in order to tell you that, let me remind you of what I'm sure is the most famous equation in all of the history. E equals mc squared. What does this mean? It means that the energy of an object at rest is equal to its rest mass times the square of the speed oflight. Now there's another equation, not quite as famous, but one I like very much. And that says the energy of a photon is equal to Its
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