50 Years Ago

The economic utility of the mineral deposits within the more distant future may primarily depend on how much the cost of trips to the Moon can be reduced, particularly through the advent of the atomic rocket. With the gradual exhaustion of the small number of top grade terrestrial deposits our mining techniques and metallurgy tend to become more and more adapted toward the exploration of lower grade and more extensive deposits. It may be that a considerable number of top grade deposits ... will be found on the surface of the Moon. Another potential economic advantage may be that the lunar deposits may, to some extent, compensate the terrestrial ones because of the different conditions which prevailed in the course of their genesis.

From Nature 9 September 1967

100 Years Ago

During the total phase of the eclipse by the moon on July 4–5, 1917, it was remarked by several observers that the brightness of the disc was sensibly greater near the limb than towards the centre. It has been suggested ... that this appearance may possibly indicate a feeble luminosity of the surface of the moon. An experiment which appears to support this view is described by M. Nodon. A brass ball ... was placed in a dark box, of which only one side was open, and was viewed in a feeble light; the appearance observed was that of a disc brightest at the centre ... in the case of a sphere which was uniformly coated with a slightly phosphorescent substance, the luminosity was greater at the edges than at the centre. Phosphorescence of some of the materials composing the lunar surface is accordingly suggested as a possible explanation of the distribution of luminosity observed during the eclipse.

From Nature 6 September 1917Footnote 1