Antiquity of the World

{mostoc} Various attempts have been made to establish the age of the world. Two groups of scientists have especially busied themselves with this question: physicists and geologists. The most notable attempt is that of the physicist Thomson (Lord Kelvin), who based his calculations on Laplace's theory that the earth originated in a fiery fluid magma. While in this magmatic state, the earth as a whole must have reacted to the attraction of the moon as the oceans now do, with ebb and flow. These constant and strong tides must in long intervals have retarded the rotation of the earth to such an extent that 7200 million years ago the earth must have rotated with double its present rapidity. Again, the polar flattening of the earth was likewise caused by this rotation, and Thomson calculated that this flattening could not have been effected to such a degree if the terrestrial crust had been solid, and the rotation of the earth the same as today. Consequently, from the extent of the flattening a conclusion may be drawn as to the rapidity of the rotation at the time of the superficial solidification of the globe. Thomson reckoned that, so long as the earth revolved double as quickly, the flattening at the poles must have been much greater than now, and thus estimated that the solidification of the terrestrial crust occurred less than 1000 million years ago. Thomson later approached the same problem in another way, by using Fourier's laws of thermal conductivity to arrive at the time elapsed since the upper crust became solid. His hypothesis was that at the moment of solidification the whole earth (its covering of stone and its kernel of iron) must have been of the same temperature (about 3000 degrees Celsius), and that the geothermic level on the upper surface must have been twenty-eight metres; consequently, the time elapsed was in round numbers 100 million years. Some of these suppositions are, however, uncertain. Thus, the initial temperature at the moment of the solidification of the terrestrial crust was set at too high a figure, and the geothermic level was rated too low. Besides, heat-producing processes (e.g., melting heat, heat of chemical composition, radio-active heat, etc.) were not taken into consideration, although these greatly retarded the cooling of the earth. On hypotheses similar to those employed by Lord Kelvin are based the calculations of 0. Fischer, who places the age of the world at 33 million years, and, those of Dawison, Mellard Reade, and H.G. Darwin, who place it at 100 million years. +