saturn's ring

from The Century Dictionary.

• noun The idea that the ring might consist of separate small particles moving like independent moons had been suggested by Cassini and Wright, in the eighteenth century, as well as by Roberval, but had attracted little attention until the work of Peirce. A little later (1857) Clerk-Maxwell showed that no ring could be permanent unless so constituted, and that such a ring might be. Since then there has been a general acceptance of this theory. It has received observational confirmation from Seeliger's photometric work upon the reflecting power of the ring, and more recently from Keeler's spectroscopic demonstration that the inner edge of the ring moves more swiftly than the outer, an observation since confirmed by several other spectroscopists.