And, of course, Einstein isn't finished. Later in 1905 comes an extension of special relativity in which Einstein proves that energy and matter are linked in the most famous relationship in physics: E = mc2. (The energy content of a body is equal to the mass of the body times the speed of light squared.) At first, even Einstein does not grasp the full implications of his formula, but even then he suggests that the heat produced by radium could mark the conversion of tiny amounts of the mass of the radium salts into energy.
In sum, an amazing outburst: Einstein's 1905 still evokes awe. Historians call it the annus mirabilis, the miracle year. Einstein ranges from the smallest scale to the largest (for special relativity is embodied in all motion throughout the universe), through fundamental problems about the nature of energy, matter, motion, time, and space—all the while putting in 40 hours a week at the patent office.
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