Published online by Cambridge University Press: 01 May 2009
The possibility of change in the position of the Earth's axis seems periodically to attract attention. This is happening now. Professor Haughton has written upon this subject, Sir William Thomson has alluded to it, while two important papers have been read upon it, one by Professor Twisden before the Geological Society, the other by Mr. George H. Darwin before the Royal Society. This article is an endeavour to exhibit to the general reader the assumptions with which they have started, and the results they have obtained.
1 Suppose the Sun's attraction at any instant to be causing in the Earth a beginning of a rotation about any diameter through the Equator. Twelve hours later this diameter will have turned with the Earth's diurnal motion so as to lie in the same line but reversed. The rotation produced at the former line will be in the opposite direction to that now being caused, and will be neutralized by it. The afternoon will undo the morning's work. This explanation is very insufficient, giving no account of Precession, but it may assist those unacquainted with Rigid Dynamics in comprehending how the Sun may be perpetually drawing the Earth's equator towards coincidence with the Ecliptic, yet never bringing it any nearer.