Einstein’s famous equation is certainly one of the most brilliant and beautiful scientific discoveries—but it’s also one of the most disturbing. The power explained by the equation really rests in the c², or the speed of light (186,282 miles per second) times itself, which equals 34,700,983,524. When that’s your multiplier, you don’t need much mass—a smidgen of plutonium is plenty—to create enough energy to destroy a city.
The Aztecs slaughtered tens of thousands of people to inaugurate the Great Pyramid of Tenochititlan. Recent archaeological findings suggest that is was common for people around the world to ritually kill—and sometimes eat—other people. (North Wind Picture Archives / Alamy).