Light emitted from a rotating source undergoes a differential type of this process, and a Boltzmann-distributed group of atoms will result in its namesake broadening of spectral lines. Hubble developed his concept of an expanding universe based on this phenomenon, which is responsible for the red shifting of visible light from galaxies moving away 
Light emitted from a rotating source undergoes a differential type of this process, and a Boltzmann-distributed group of atoms will result in its namesake broadening of spectral lines. Hubble developed his concept of an expanding universe based on this phenomenon, which is responsible for the red shifting of visible light from galaxies moving away from the Earth. In general cases, it leads to higher frequency waves for approaching objects and lower frequencies for receding objects. For 10 points, name this effect that accounts for the drop in pitch from a passing siren.
Light emitted from a rotating source undergoes a differential type of this process, and a Boltzmann-distributed group of atoms will result in its namesake broadening of spectral lines.
{Doppler} effect