Museo Galileo
Virtual Museum
Apparatus for showing the effects of the centrifugal force
    • Setting:
      Room XII
    • Maker:
    • Date:
      late 18th cent.
    • Materials:
      wood, iron, brass
    • Dimensions:
      650x720x800 mm
    • Inventory:
    • Apparatus for showing the effects of the centrifugal force (Inv. 1384)

This instrument, like the apparatus inv. 1027, is used to perform experiments on the centrifugal force. The wooden base carries a hinged board whose slope can be adjusted by a metal arc and a fastening screw. The board supports a vertical frame carrying a wheel fitted with a handle. The handle, via a lathe and pulley, rotates a horizontal iron axle bearing two perpendicularly placed elastic metal blades that form two meridians of a sphere. When the axle is spun, the centrifugal force distorts the blades, turning the sphere into a rotating ellipsoid whose flatness increases in proportion to the velocity. There is a mechanism for blocking the blades at the point of maximum flattening. The apparatus thus offers a convincing demonstration of the cause of the Earth's flattening at the poles, which is precisely the vortical rotation of our planet on its axis. The instrument also came with a glass globe (missing) to replace the axle with blades. The globe was filled with a mixture of water and a liquid of different density, or with water containing a wax pellet or an air bubble. With such combinations, the globe provided a demonstration of the effects of gravity combined with the centrifugal force. The operating principle of the apparatus was described by Jean-Antoine Nollet in Leçons de physique expérimentale (Paris, 1743-1748). Provenance: Lorraine collections.