George Gabriel Stokes (August 13, 1819 - February 1, 1903), was an Irish mathematician and physicist. His first published papers (1842-43) were on the steady motion of incompressible fluids and some cases of fluid motion. These were followed in 1845 by one on the friction of fluids in motion and the equilibrium and motion of elastic solids. His work on fluid motion and viscosity led to his calculating the terminal velocity for a sphere falling in a viscous medium. This became known as Stokes' law. His best-known researches deal with the wave theory of light. His first papers on the aberration of light appeared in 1845-46, and were followed in 1848 by one on the theory of certain bands seen in the spectrum. In 1852, in his paper on the change of wavelength of light, he described the phenomenon of fluorescence, as exhibited by fluorspar and uranium glass, materials which he viewed as having the power to convert invisible ultra-violet radiation into radiation of longer wavelengths that are visible. He was secretary, then president, of the Royal Society. He died in 1903 at the age of 83.