Fourier’s theorem was one of the most significant mathematical results of the 19th century because phenomena in many fields—from optics to quantum mechanics, and from seismology to electrical engineering—can be modeled by periodic waves. Often, the best way to investigate these waves is to break them down into simple sinusoids.
In 1798 Joseph Fourier, a 30-year-old professor at the École Polytechnique in Paris, received an urgent message from the minister of the interior informing him that his country required his services, and that he should “be ready to depart at the first order.” Two months later, Fourier set sail from Toulon as part of a 25,000-strong military fleet under the command of General Napoleon Bonaparte, whose unannounced objective was the invasion of Egypt.
Fourier was one of 167 eminent scholars, the savants, assembled for the Egyptian expedition. Their presence reflected the French Revolution’s ideology of scientific progress, and Napoleon, a keen amateur mathematician, liked to surround himself with colleagues who shared his interests.
It is said that when the French troops reached the Great Pyramid at Giza, Napoleon sat in the shade underneath, scribbled a few notes in his jotter and announced that there was enough stone in the pyramid to build a wall 3 meters high and a third of a meter thick that would almost perfectly encircle France.
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