In 1851 J. B. L. Foucault provided the first mechanical demonstration of the earth's diurnal rotation with a vibrating pendulum. He performed the experiment in the Pantheon in Paris, sparking a pendulum mania that raged across Europe and the United States. The interest in the Foucault pendulum provides an opportunity to examine the popularization of physical science in the antebellum United States. Laypersons attended public demonstrations, performed their own demonstrations, and disputed the principles of the Foucault pendulum. Their participation in (...) physical science made them part of the American scientific community. These lay scientists performed most of the public demonstrations of the experiment. Some researchers performed public demonstrations, but others avoided this opportunity to popularize, deeming it unseemly to participate in pendulum mania. The geographical distribution of interest in the experiment challenges assertions made by historians about the relative level of scientific activity in the New England, mid-Atlantic, southern, and western regions of the United States. (shrink)