Gravitational redshift

In the general theory of relativity by

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Albert Einstein, the gravitational redshift or Einstein shift

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

is the effect that clocks in a gravitational field tick slower when observed by a distant observer. More specifically the term refers to the shift of wavelength of a photon to longer wavelength (the red side in an optical spectrum) when observed from a point in a lower gravitational field. In the latter case the 'clock' is the frequency of the photon and a lower frequency is the same as a longer ("redder") wavelength.

Related Topics:
Photon - Optical spectrum

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The gravitational redshift is a simple consequence of the

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Einstein equivalence principle ("all bodies fall with the same acceleration,

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

independent of their composition") and was found by Einstein eight years before

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

the full theory,(of relativity). A version of the effect (the gravitational weakening of light from high-gravity-stars) was also predicted by John Michell, using Newtonian arguments, in 1783 in "Transactions of the Royal Society". Einstein's achievement was to rediscover the effect, examine it in detail, and recognise that it led inevitably to gravitational time dilation. This was a new result.

Related Topics:
John Michell - 1783 - Royal Society - Gravitational time dilation

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Observing the gravitational redshift in the solar system is one of the classical tests of general relativity.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~