* This is no small effect! One 14.4 keV gamma-ray emitted by ⁵⁷ Co from a 1 gram Fe chunk imparts a velocity to the chunk of 7.7 × 10⁻²¹ cm/s or roughly 2.4 Ångstroms/Century.

^† Don't be concerned if the absorber is clamped to something, because then the whole building or planet will move and that only slows matters by a few more Orders of magnitude.

^‡ Relative Sociological Effectiveness (RSE) is a measure of the capacity of specific ionizing radiation to produce a specific sociological effect expressed relative to a reference radiation such as one Standard medical x-ray exposure. There is a theoretically unjustifiable empirical correlation with the ratio of the mass media absorption coefficient to the attempt frequency (decay rate) of the source.