In 1850, despite the quest of many learned men including Nicholas Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei and others, no absolute proof existed that Earth rotated. But Léon Foucault changed that status at 2 a.m. on January 6, 1851. The amateur scientist’s experiment with a pendulum in the cellar of his home clearly demonstrated that at which much evidence and many previous discoveries had hinted.

Foucault already had built a small steam engine, improved Daguerre’s photographic methods, improved lighting for the use of the microscope, and developed a regulator for stage lighting. The untrained but confident man’s latest revelation was about to embarrass the French Academy of Sciences and flaunt church tradition.

His finding should have vindicated his predecessors in the eyes of the church and brought him into full acceptance by his peers. Foucault applied many times, but was refused acceptance into the Academy. While he had friends within the scientific elite and served as science editor of the newspaper Journal des Débats covering their findings, many of his peers still opposed him. Their continued indifference would have left this brilliant man in obscurity.

The destiny of Louis-Napoléon Bonaparte changed Foucault’s fortune. The Prince-President and eventual Emperor was also a self-taught scientist who brought Foucault into the public limelight. Napoléon III later created a position for him as Physicist Attached to the Imperial Observatory in Paris.

Amir D. Aczel’s book is rich in scientific, mathematical and political history. However, he competently provides the information on the layman’s level making complex concepts understandable. This study of Foucault ties him to the nineteenth century as a gifted engineer with access to the developments of the Industrial Revolution.