In the Book Big Bang by Simon Singh, he mentions that cooler stars are more red. How is this different from a red shift? i.e., if all spectra are red shifted, how can we tell whether it's due to the star receding or from being cooler?
Speed guns and laser doppler velocimetry refer to doppler shift caused by the REFLECTION of light. GPS is by trilateration of radio signals. Red shift of stars is taught as caused by movement of light from its primary source i.e. not shifted by reflection.
Is there empiric laboratory...
I'm aware of the doppler effect for sound waves. But light waves are different, e.g., light travels through a vacuum but sound does not. Has there been any laboratory confirmation for red shift for LIGHT. I could find only ONE paper by Bélopolsky, A. in 1901 using rotating mirrors. But there...