(Phys.org)--A trio of researchers, two with the University of California, the third with Sharif University of Technology, in Iran, has found that a common ring, such as is worn on the finger, spins differently on a tabletop than does a coin. In their paper published in Physical Review Letters, Mir Abbas Jalali, Milad Sarebangholi and Reza Alam describe their tests and observations and offer a theory on why a spinning ring behaves the way it does.