WILL RADIUM FINALLY BURN UP THE EARTH?

Lake Wakatip Mail, Issue 2904, 31 January 1911, Page 7

WILL RADIUM FINALLY BURN UP THE EARTH?

In the early days of radium Prof. Joly suggested that its presence in the earth might retard its rate of cooling,, and thus permit a longer time for earth history than Lord Kelvin was prepared to allow. And when it became possible to measure the actual amount of radium in the earth's crust, and to determine accurately its beating powers, the means were at hand to calculate the exact value of its effect in keeping the earth warm. And the remarkable result was arrived at that not only is the radium in the earth sufficient to prolong indefinitely its cooling, but that it ought to be actually raising its temperature ! To escape the difficulty suggested by this result it is thought by some that the radium content of the mass of the earth must be less than that of the rocky crust which has been determined by observation. But there seems to be no 'a priori* reason for supposing this, nor has any diminition of radium with depth been observed in the rocks which have been examined. And in his "Radioactivity and Geology,," Professor Joly suggests an interesting alternative. Let us suppose that the one-bil-lionth of its mass of radium, which has been determined as the proportion for the rocky crust, is continuous throughout the earth. This need not imply a never-cooling earth, for, as Professor Joly points out, the deeper parts of the earth are thermally isolated for immense periods from the surface. Thus the interior parts of the earth

may go on rising indefinitely in temperature without any evidence of the heat reaching the surface. If the requisite amount of radium is present they may be doing so now. This may go on indefinitely for untold ages until an enormous internal temperature is attained. But it cannot go on for ever. Home day the great internal heat reservoir must, as it were, hurst its bonds. There will be a flow of heat outward in all directions to th» surface, and the earth will be reduced again to its original molten state. Such, suggests Trofessor Joly, in the course of a paper, may be the end of the present geological age, and with such another melting up of a cooled globe it may have begun.