High Quality Content by WIKIPEDIA articles! Alexey Maksimovich Fridman was a Soviet physicist specializing in astrophysics, physics of gravitating systems and plasma physics. He discovered new types of instabilities in gravitating media, created the theory of planetary rings and predicted the existence of small Uranus satellites that were later discovered. He also developed hydrodynamic theory of the spiral structure in galaxies. Fridman worked at the Institute of Astronomy of the Russian Academy of Sciences, INASAN , and was professor of Moscow Institute of Physics and Technology and Moscow State University.