Radiation of a massive classical scalar field from a point source is studied in the mass zero limit and compared with the radiation emitted in a mass zero theory. The total radiated energy momentum is the same in both theories, but the rate cannot be got in the massive theory. The massive theory admits a particle number-probability interpretation, and a speed distribution and energy distribution can be found. The energy distribution goes like ω-(2n+1) at high energies, the value of n depending on smoothness properties of the source world line. In the low ω region it is proportional to ω-1 until (ω - m) m ≪ 1, where a strong suppression factor proportional to ν2 dominates. But despite this fact the radiated number diverges like log m-1 owing to contributions from particles with energies O(m0) but with ultrarelativistic speeds. Other interesting features have to do with speed distribution properties in the m → 0 case. © 1969.
