In physics (especially astrophysics), redshift happens when light or other electromagnetic radiation from an object moving away from the observer is increased in wavelength, or shifted to the red end of the spectrum. In general, whether or not the radiation is within the visible spectrum, "redder" means an increase in wavelength – equivalent to a lower frequency and a lower photon energy, in accordance with, respectively, the wave and quantum theories of light.
Redshifts are an example of the Doppler effect, familiar in the change in the apparent pitches of sirens and frequency of the sound waves emitted by speeding vehicles. A redshift occurs whenever a light source moves away from an observer. Cosmological redshift is seen due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase in their distance from Earth. Finally, gravitational redshifts are a relativistic effect observed in electromagnetic radiation moving out of gravitational fields. Conversely, a decrease in wavelength is called blueshift and is generally seen when a light-emitting object moves toward an observer or when electromagnetic radiation moves into a gravitational field.
Although observing redshifts and blueshifts have several terrestrial applications (such as Doppler radar and radar guns), redshifts are most famously seen in the spectroscopic observations of astronomical objects.
A special relativistic redshift formula (and its classical approximation) can be used to calculate the redshift of a nearby object when spacetime is flat. However, many cases such as black holes and Big Bang cosmology require that redshifts be calculated using general relativity. Special relativistic, gravitational, and cosmological redshifts can be understood under the umbrella of frame transformation laws. There exist other physical processes that can lead to a shift in the frequency of electromagnetic radiation, including scattering and optical effects; however, the resulting changes are distinguishable from true redshift and not generally referred as such (see section on physical optics and radiative transfer).
Other articles related to "red shift, shifts":
... The red shift caused by the curvature of space-time, a time dilation expressed by the metric component, is suffered not only by the photon but also by the atom with which it interacts and is thus ... The red shift that is detectable is caused by the increase in rest mass that fundamental particles undergo when raised to the higher level ... Gravitational red shift in this theory is interpreted not as a loss of gravitational potential energy by the photon but as a gain of gravitational potential energy by the apparatus measuring it ...
... Red Shift's two initial releases were designed, but not coded, by Gollop just after he left school (Time Lords and Islandia) ... and coding Nebula and Rebelstar Raiders for Red Shift ... In 1984, a group of Harlow-based Red Shift programmers split off to form SLUG ...
... is under orders to help the other remaining former heralds Red Shift and Firelord as they combat the Annihilation wave fleet ... and Galactus now captured and Firelord half-dead, Stardust and Red Shift are the only two active heralds ... Stardust and Red Shift were presumed dead after holding back a massive energy blast from Galactus' absorbing device ...
... transfer and physical optics can result in shifts in the wavelength and frequency of electromagnetic radiation ... In such cases the shifts correspond to a physical energy transfer to matter or other photons rather than being due to a transformation between reference frames ... These shifts can be due to such physical phenomena as coherence effects or the scattering of electromagnetic radiation whether from charged elementary particles, from particulates, or from fluctuations of ...
Famous quotes containing the words shift and/or red:
“What is the life of man! Is it not to shift from side to side?from sorrow to sorrow?to button up one cause of vexation!and unbutton another!”
—Laurence Sterne (17131768)
“The silence is death.
It comes each day with its shock
to sit on my shoulder, a white bird,
and peck at the black eyes
and the vibrating red muscle
of my mouth.”
—Anne Sexton (19281974)