  A photon source is located in a rotating waveguide. An absorber with a sharp
absorbing frequency absorbs some of the emitted photons. This decreases the
number of photons which are detected by a detector. The frequency (energy)
spectrum measured in the absorber depends on the setup (the positions of the
source and the detector), and this spectrum determines the amount of
absorption. The shifts are calculated for different configurations. Among other
things, it is seen that even if the source and the absorber are at rest (while
the waveguide is rotating), there is a nonzero frequency shift.
