Our Unstable Globe

The gist of a dissertation* recently prepared for Nature (London) by Professor W. de Sitter of the University of Leyden, Netherlands:

It has long been suspected that the rotation of the earth is gradually slowing down. But lately other doubts have arisen. As a matter of fact, it is not the rotation of the earth, but of a definite point on the earth--the Greenwich or some other observatory--that is used as our standard. Comparison of wireless time signals has revealed slight discrepancies from different observatories. While these may be due to errors in instruments, it is quite possible that the earth does not rotate as a rigid body, but that some parts of its surface are moving in relation to other parts. Similar irregularities have been observed in the moon's rotation, and even in Mercury, Venus and the sun, for which no explanation has been found. In short, there is distinct evidence of slow and continuous changes, imperceptible to the human senses, due to the sliding of the earth's crust over its core. Instead of being on a solid ball, as we had supposed, we may really be on a shimmying, jelly-like globe!

*Problems of Fundamental Astronomy.