The first classical model for spin proposed small rigid particle rotating about an axis, as ordinary use of the word may suggest. Angular momentum can be computed from a classical field as well. By applying Frederik Belinfante 's approach to calculating the angular momentum of a field, Hans C. Ohanian showed that "spin is essentially a wave property... generated by a circulating flow of charge in the wave field of the electron". This same concept of spin can be applied to gravity waves in water: "spin is generated by subwavelength circular motion of water particles".