“Almost exactly two days later. When it was made the moon was nearly nine and a quarter days old, and its age at the time No. 7 was made was only seven and a quarter days. But, owing to the effects of libration, an explanation of which I have put into a note for your private reading when you feel like it, [see p. 57, footnote], the difference of phase amounts to less than two days. You are right, however, in remarking that sunrise is a very slow process on the moon. It requires about two weeks to pass from the western side of the moon to the eastern side, and both day and night at any point on the moon last about a fortnight. This results from the fact that, as I have told you, the moon does not turn rapidly on its axis like our own globe, but keeps always the same side directed toward the earth. Accordingly, a lunar day and night are together about a month long.” “And was it so when, as I must persist in believing, there were inhabitants on the moon?” “Probably, although it may have been shorter then. The consequences of these excessively long days and nights would be very serious to beings fashioned upon the terrestrial plan. In the practical absence of an atmosphere the heat of the sun’s rays, pouring down without interruption and without the intervention of any clouds or vapors for fourteen days at a time, must be simply overpowering. And then, during the equally long night that ensues, the radiation into open space must quickly leave the surface of the moon exposed to the most frightful degree of cold, comparable with the absolute zero of empty space!” “But think, what a merciless environment you are picturing for my inhabitants of the moon. Please do not forget that I insist that their comfort shall be considered.” “Oh, as for that, you know you were content a little while ago to relegate your inhabitants to a remote period in the past, after the volcanic fury of the lunar world had ceased, and before its present airless and waterless condition had supervened. Possibly at that time things were not so uncomfortable for them. They may have had clouds to temper the sunshine, rains to cool the days and dews the nights, and shady parks like yours for philosophic and scientific contemplation.” “Do not forget the poets.”