Quote:
Originally Posted by Archy
I can understand a redshifted spectrum: how can the "redshift" of a single proton be measured  |
Photon....not proton. Very easily, with a photomultiplier tube and in exactly the same way as you measure a redshifted spectrum. You look at (or determine via theory) what the original wavelength/frequency of the photon was when it left the source and compare that with what you measured at the photomultiplier.