Comment on an Effect Proposed by A.G. Lebed in Semiclassical Gravity
  A.G. Lebed has given an argument that when a hydrogen atom is transported slowly to a different gravitational potential, it has a certain probability of emitting a photon. He proposes a space-based experiment to detect this effect. I show here that his arguments also imply the existence of nuclear excitations, as well as an effect due to the earth's motion in the sun's potential. This is not consistent with previous results from underground radiation detectors. It is also in conflict with astronomical observations. 
B. Crowell
nucl-ex gr-qc