Gravitational Red Shifting
Red shifting, of course, indicates an elongating of the wavelength. An elongated wavelength indicates that the radiation has lost some of its energy from the instant it left its source.
As predicted by Einstein, radiation also experiences a slight amount of red shifting due to gravitational influences. Gravitational red shifting is due to the change in the strength of gravity and occurs mostly near massive bodies. For example, as radiation leaves a star, the gravitational attraction near the star produces a very slight lengthening of the wavelengths, as the radiation loses energy in its effort to escape the pull of gravity from the large mass. This red shifting diminishes in effect as the radiation travels outside the sphere of influence of the source’s gravity.