Leon Foucault's dramatic demonstration of the rotation of the Earth using a freely-rotating pendulum in 1850 shocked the world of science. Scientists were stunned that such a simple proof of our planet's rotation had to wait so long to be developed. Foucault's public demonstration, which was repeated at many locations around the world, put an end to centuries of doubt about the Earth's rotation--skepticism that had been bolstered since antiquity by Aristotelian philosophy and scripture. This paper puts Foucault's pendulum experiments in context, surveying the life and work of this extraordinary physicist, a man who achieved much--including work on measuring the speed of light, microscopy, astronomy, and photography--without formal training in the sciences.