Foucault pendulum, 1988.
© Science Museum / Science & Society Picture Library
Made by Profesor Brian Pippard in the workshops of the Cavendish Laboratory in Cambridge, Kent in 1988, this Foucault Pendulum has been demonstrating the Earth's rotation at the Science Museum since 1988. Unlike its predecesor, this pendulum runs continually, thus avoiding the need to re-swing the pendulum each hour. Gently raising and lowering the pendulum pivot, using a motor in conjunction with a sensor, keeps the pendulum in motion. Known as 'parametric amplification', it uses the same principle which keeps a child's swing in motion. The French physicist Leon Foucault (1819-1868) conceived the display and first demonstrated it at the Parisian Pantheon in 1851.