We apply a new formalism to calculating emission of light from sheared dielectric surfaces. When the surfaces are smooth, the emission of light requires extreme velocities, but introducing surface roughness with short-period components reduces the extreme demands on velocity so that, for atomic-scale roughness, shear velocities as small as 104ms-' will result in light emission. Some order-of-ma...

Up to now little attention has been paid to an expression for the velocity of light in a gravitational field derived by Einstein in 1911. It is shown that (i) this expression represents the proper velocity of light (since it is defined in terms of proper time and length), (ii) the proper velocity of light is anisotropic in non-inertial reference frames, and (iii) unlike the coordinate velocity ...