Matter appeared within the first second after the big bang. Matter is the stuff that energy pushes around. Until just over a century ago, scientists and philosophers assumed that matter and energy were distinct. We now know that matter is really a highly compressed form of energy. The young Albert Einstein demonstrated this in a famous paper in 1905. That formula—energy (E) is equal to mass (m) times the speed of light (c) squared, or E = mc2—tells us how much energy is compressed inside a given amount of matter. To figure out how much energy is locked up in a bit of matter, multiply the mass
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