How does a gravitational redshift differ from a doppler shift?
1 Answer
Mar 5, 2016
A “gravitational redshift” is the frequency (speed) change of a photon (light) in a gravitational field.
Explanation:
A “Doppler shift” is a more generic description of the phenomenon of a wavelength shift due to external forces. Light and sound both exhibit doppler shifts when they are part of a moving object (Airplanes, planets, trains). The incoming perspective is compressed – a “blue shift” - and the outgoing (receding) one is expanded – a “red shift”.
The term "red shift" comes from the movement of light frequencies to the longer “red” wavelengths. Other electromagnetic wavelengths will exhibit similar shifts, but not necessarily becoming “redder”.
