Measuring a galaxy's redshift tells how long ago its light was emitted.
The thing about photons is that they redshift, losing energy as space expands.
redshift shows the spacetime between galaxies is expanding.
The amount of a galaxy's redshift tells astronomers how fast the galaxy is moving away from us.
Over vast distances in the universe, this predicts that redshift of the gauge bosons weakens the gravitational coupling constant.
The bigger uncertainty is whether supernovae at high redshift are qualitatively different from local supernovae.
Its explanations of cosmic expansion, redshift and cosmological horizons are superb.
Their redshift indicates how much the universe has expanded since then.
The redshift dependence is both a blessing and a curse.
Your question about the redshift of a single photon is a great one.
British Dictionary definitions for redshift
a shift in the lines of the spectrum of an astronomical object towards a longer wavelength (the red end of an optical spectrum), relative to the wavelength of these lines in the terrestrial spectrum, usually as a result of the Doppler effect caused by the recession of the object Compare blueshift