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Redshift and blueshift. If a source of the light is moving away from an observer, then redshift (z > 0) occurs; if the source moves towards the observer, then blueshift (z < 0) occurs. This is true for all electromagnetic waves and is explained by the Doppler effect. Consequently, this type of redshift is called the Doppler redshift.
The opposite effect, in which photons gain energy when travelling into a gravitational well, is known as a gravitational blueshift (a type of blueshift). The effect was first described by Einstein in 1907, [ 3 ] [ 4 ] eight years before his publication of the full theory of relativity .
The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. [ 1 ] [ 2 ] [ 3 ] The Doppler effect is named after the physicist Christian Doppler , who described the phenomenon in 1842.
The transverse Doppler effect is one of the main novel predictions of the special theory of relativity. [7] Whether a scientific report describes TDE as being a redshift or blueshift depends on the particulars of the experimental arrangement being related.
Redshift-space distortions (RSDs) manifest in two particular ways. The Fingers of God effect is where the galaxy distribution is elongated in redshift space, with an axis of elongation pointed toward the observer. [1] It is caused by a Doppler shift associated with the random peculiar velocities of galaxies bound in structures such as clusters.
[p 4] The measurement of gravitational redshift and blueshift by this experiment validated the prediction of the equivalence principle that clocks should be measured as running at different rates in different places of a gravitational field. It is considered to be the experiment that ushered in an era of precision tests of general relativity.
That motion would create a redshift of the eclipsed star's spectrum followed by a blueshift, which would thus appear as a change in the measured radial velocity in addition to that caused by the orbital motion of the eclipsed star. [2] [3] The effect is named after Richard Alfred Rossiter and Dean Benjamin McLaughlin. [4]
The blueshift of a falling photon can be found by assuming it has an equivalent mass based on its frequency E = hf (where h is the Planck constant) along with E = mc 2, a result of special relativity. Such simple derivations ignore the fact that in general relativity the experiment compares clock rates, rather than energies.