PARISIANS flocked to the Panth茅on last weekend just as they did 144 years ago, to see how the pendulum devised by French physicist Jean Bernard L茅on Foucault proves that the Earth turns on its axis. As part of France鈥檚 annual science festival, the original 28-kilogram sphere used by Foucault was brought out from a museum collection, dusted off and hung by piano wire from the Panth茅on鈥檚 dome, just as in 1851.
As the iron ball swings back and forth in a plane, the Earth rotates beneath it, so the pendulum鈥檚 plane turns slowly relative to the ground. At the Panth茅on, the rotation is traced in wet sand. Foucault first observed the phenomenon with a smaller pendulum hung in the basement of his Paris home. The demonstation was then set up at the Paris Observatory and later the 67-metre pendulum was hung from the dome of Panth茅on.
