text: The Foucault pendulum , or Foucault 's pendulum , named after the French physicist LÃ on Foucault , is a simple device conceived as an experiment to demonstrate the rotation of the Earth .
simplified: The Foucault pendulum , or Foucault 's pendulum ( named after the French physicist LÃ on Foucault ) was created as an experiment to show the rotation of the Earth .