Redshift

:This article is about the light phenomenon. For other uses of the phrase "Red Shift", see Red Shift

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Redshift describes a change in the wavelength of light, in which the wavelength is longer, or redder, than when it was emitted at the source. This can happen when the source moves away from the observer, known as the Doppler effect. It is also observed when light emitted by distant galaxies is shifted to longer wavelengths than the spectrum of closer galaxies. This is taken as evidence that the universe is expanding and that it started in a Big Bang.

Related Topics:
Light - Doppler effect - Galaxies - The universe is expanding - Big Bang

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In general, redshift (and blueshift, the observation of shorter wavelength light than emitted) is quantified by

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z = rac{f_{mathrm{emitted}} - f_{mathrm{observed}}}{f_{mathrm{observed}}} = rac{lambda_{mathrm{observed}} - lambda_{mathrm{emitted}}}{lambda_{mathrm{emitted}}}

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where f is frequency and λ is wavelength.

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