Red shift and blue shift in astronomy. Diagram of the Doppler effect, the change in the wavelength of radiation due to the motion of a source (galaxy Stock Photo - Alamy
Learn about the Doppler Effect
Red Shift Definition, Types & Uses - Lesson | Study.com
The Doppler effect | Red-shift | Calculating speeds of galaxies
General Astronomy/The Doppler Effect - Wikibooks, open books for an open world