gravitational red shift

physics

Also known as: gravitational redshift

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 17, 2026

Quick Summary

Gravitational redshift is a phenomenon where the frequency of light decreases, shifting it towards longer, redder wavelengths, as it travels away from a source of gravity. This occurs because light, like mass, is affected by gravitational forces. As light moves away from a massive object, it loses energy, causing its frequency to drop and its wavelength to increase. This effect is a prediction of Einstein's theory of general relativity and has been experimentally verified. The stronger the gravitational field, the more pronounced the gravitational redshift. This phenomenon is distinct from the Doppler effect, which causes redshift due to the relative motion between an observer and a light source.123

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

5 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

astronomy
Testing relativity
…predicted by Einstein was the gravitational redshift. Light coming from a compact massive object should be slightly redshifted; that is, the light should have a longer wavelength. Measuring this was a delicate business, as the expected shift was small and could easily be masked by other effects. Attempts to measure…
Read More
…predicted by Einstein was the gravitational redshift. Light coming from a compact massive object should be slightly redshifted; that is, the light should have a longer wavelength. Measuring this was a delicate business, as the expected shift was small and could easily be masked by other effects. Attempts to measure…
Read More

Mössbauer effect
Applications
…a direct demonstration of the gravitational red-shift; i.e., the change in the energy of a quantum of electromagnetic radiation as it moves through a gravitational field. This was accomplished by measuring the Doppler shift required to compensate for the change in the energy of the gamma ray resulting from a…
Read More
…a direct demonstration of the gravitational red-shift; i.e., the change in the energy of a quantum of electromagnetic radiation as it moves through a gravitational field. This was accomplished by measuring the Doppler shift required to compensate for the change in the energy of the gamma ray resulting from a…
Read More

relativity
Experimental evidence for general relativity
…directly and also through the gravitational redshift of light. Time dilation causes light to vibrate at a lower frequency within a gravitational field; thus, the light is shifted toward a longer wavelength—that is, toward the red. Other measurements have verified the equivalence principle by showing that inertial and gravitational mass…
Read More
…directly and also through the gravitational redshift of light. Time dilation causes light to vibrate at a lower frequency within a gravitational field; thus, the light is shifted toward a longer wavelength—that is, toward the red. Other measurements have verified the equivalence principle by showing that inertial and gravitational mass…
Read More