Simple Description

An apparent change in wavelength of light emitted by something that is moving away from us.

Further Detail

For example, if a star is moving away from us then the light from the star will appear to be red-shifted (in other words, the wavelength of the light is longer than it would normally be). The existence of red shift is evidence that stars are moving away from us - evidence for the Big Bang Theory of the formation of the universe. The larger the red shift, the faster the star is moving and therefore the further away it is.

Related Words:

• Big Bang Theory
• Doppler Effect

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