A theoretical calculation is given for the ''scintillations'' or fluctuations of cosmic rays expected to be observed during quiet times by a detector in interplantary space or on the lunar surface. Interplanetary scintillations caused by fluctuation in the interplanetary magnetic field are not sufficient to explain the power spectrum recently reported by Benson et al. (1981) from a detector on the moon. Their inferred cosmic-ray fluctuations are considerably larger than observed during undisturbed periods by ground-based and satellite experiments.