Letter from Thomas Gold, to Professor John Simpson, Enrico Fermi Institute, University of Chicago, Chicago 37, Illinois On Kopal's claim to have deduced the possibility of lunar luminscence from Simpson's figure for relativistic proton flux from the sun. Kopal's annoyance at Gold's assertion of the error. 'Such a story cannot be allowed to pass, and I am sure not with your name even indirectly involved'. 10 September 1964