Foucault’s Pendulum – See the Earth rotate!

Weather station, transmission mast, vantage point and home to a famous pendulum: the Deutsches Museum Tower is much more than just the building’s landmark. The entrance on the ground floor is located between the Model Railway and the Bridges and Hydraulic Engineering exhibition. Before you make your way up to the viewing platform, either by elevator or via the more than one hundred steps, it is worth stopping beside the elevator to see the Foucault’s Pendulum in action. At the foot of the tower, a 30 kg lead ball swings back and forth on a 60-metre-long wire rope. Below the ball is a circular disc with a diameter of three metres, which indicates the compass points and on which more than 60 movable cones are placed in a semicircle. The sphere always swings in the same plane. Nevertheless, after a few minutes it knocks over one cone after the other, proving that the Earth is rotating under the pendulum. And this rotation is far from slow: at our latitude, the Earth rotates at a speed of around 1,117 km/h! To the left of the pendulum is another, much larger ball: the physicist Philipp von Jolly (1809–1884) used this lead sphere, which weighs almost 5,800kg, to determine the density of the Earth.