The redshift of light or other electromagnetic radiation caused by a strong gravitational field; also known as the Einstein shift. It arises because radiation loses energy as it passes out of the gravitational field of the emitting body. As a consequence, the frequency of the radiation decreases and its wavelength is shifted to the red end of the spectrum. The redshift at wavelength λ is given by Gmλ/c2r, where m is the mass of the body, r is the distance of the emitting region from the centre of mass, c is the speed of light, and G is the universal gravitational constant. Small gravitational redshifts are observed in transmissions between receivers at different altitudes on Earth, and between satellites and receivers on the Earth. A gravitational redshift has been observed in the light from some white dwarfs, and would result in the rapid fading out of a black hole in the process of formation as seen from outside.
Subjects: Astronomy and Astrophysics.