Kugel fountain, San Jose

A kugel fountain is a water feature or sculpture where a sphere sits in a fitted hollow in a pedestal, and is supported by aquaplaning on a thin film of water. Pressurized water flows between the sphere and socket, creating a mechanical hydrostatic bearing that is nearly frictionless. The sphere can weigh thousands of kilograms, but the efficient bearing allows it to be spun by the force of a hand. The sphere does not float, being denser than water; it is often made from granite. The hydraulics of the fountain can be controlled so that the axis of rotation of the sphere changes continually. Ring sculptures that rotate on an axis are also built. ()