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If the speed light is fixed due to relativity how can we see red or blue shifts?
- Glen Reeves
There is no problem. The red shift of light is similar to a Doppler shift of sound in air. In air you can hear the shift in frequency of a siren depending on whether it is coming toward you (higher frequency => blue shift) or away from you (lower frequency => red shift). The equations for light are quite similar when the velocities small compared to the speed of light but get a bit more complicated for higher values. Nevertheless the redshift is a well defined property of special relativity and the speed of light.
(published on 01/08/08)
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