Today is the birthday of mathematician Joseph Fourier, born in 1768 in Auxerre, France. He wore many hats during his 62 years. In 1798 he began conducting archaeological expeditions in Egypt during Napoleon's invasion. Fourier's most famous work began with experiments on the propagation of heat. Based on the results, he expressed the conduction of heat with a differential equation and used an infinite series of sines and cosines—now called a Fourier series—to solve it. Today Fourier series, as well as other mathematical techniques like Fourier transforms, are used in many areas of physics. Fourier also proposed in 1824 that gases in Earth's atmosphere could trap heat received from the Sun—a phenomenon later called the greenhouse effect.
