An Etymological Dictionary of Astronomy and Astrophysics

1. Fluid mechanics: At low velocities, the frictional force on a spherical body moving through a fluid at constant velocity is equal to 6πRηv, where R is the radius of the sphere, η the fluid → viscosity, and v the velocity.
   

2. Spectroscopy: The wavelength of → luminescence excited by radiation is always greater than that of the exciting radiation.

See also: → Stokes; → law.