The earth had a beginning

[This is from my letter to Charles Thompson, December 17, 1786, discussing the perfect astronomical structure of the Earth as if it had a creator.]

I take the first moment I can, however, to acknowledge the receipt of your letters of April the 6th, July the 8th and 30th. In one of these, you say, you have not been able to learn, whether, in the new mills in London, steam is the immediate mover of the machinery, or raises water to move it? It is the immediate mover. The power of this agent, though long known, is but now beginning to be applied to the various purposes of which it is susceptible. You observe that Whitehurst supposes it to have been the agent, which bursting the earth, threw it up into mountains and valleys. You ask me what I think of his book? I find in it many interesting facts brought together, and many ingenious commentaries on them. But there are great chasms in his facts, and consequently in his reasoning. These he fills up by suppositions, which may be as reasonably denied as granted.

A sceptical reader therefore, like myself, is left in the lurch. I acknowledge, however, he makes more use of fact, than any other writer on a theory of the earth. But I give one answer to all these theorists. That is as follows. They all suppose the earth a created existence. They must suppose a creator then; and that he possessed power and wisdom to a great degree. As he intended the earth for the habitation of animals and vegetables, is it reasonable to suppose, he made two jobs of his creation, that he first made a chaotic lump and set it into rotatory motion, and then waited the millions of ages necessary to form itself? That when it had done this, he stepped in a second time, to create the animals and plants which were to inhabit it? As the hand of a creator is to be called in, it may as well be called in at one stage of the process as another. We may as well suppose he created the earth at once, nearly in the state in which we see it, fit for the preservation of the beings he placed on it. But it is said, we have a proof that he did not create it in its present solid form, but in a state of fluidity; because its present shape of an oblate spheroid is precisely that which a fluid mass revolving on its axis would assume.

I suppose that the same equilibrium between gravity and centrifugal force, which would determine a fluid mass into the form of an oblate spheroid, would determine the wise creator of that mass, if he made it in a solid state, to give it the same spheroidical form. A revolving fluid will continue to change its shape, till it attains that in which its principles of contrary motion are balanced. For if you suppose them not balanced, it will change its form. Now, the same balanced form is necessary for the preservation of a revolving solid. The creator, therefore, of a revolving solid, would make it an oblate spheroid, that figure alone admitting a perfect equilibrium. He would make it in that form, for another reason; that is, to prevent a shifting of the axis of rotation. Had he created the earth perfectly spherical its axis might have been perpetually shifting, by the influence of the other bodies of the system; and by placing the inhabitants of the earth successively under its poles, it might have been depopulated; whereas, being spheroidical, it has but one axis on which it can revolve in equilibrio.

Suppose the axis of the earth to shift forty-five degrees; then cut it into one hundred and eighty slices, making every section in the plane of a circle of latitude, perpendicular to the axis: every one of these slices, except the equatorial one, would be unbalanced, as there would be more matter on one side of its axis than on the other. There could be but one diameter drawn through such a slice, which would divide it into two equal parts. On every other possible diameter, the parts would hang unequal. This would produce an irregularity in the diurnal rotation. We may, therefore, conclude it impossible for the poles of the earth to shift, if it was made spheroidically; and that it would be made spheroidical, though solid, to obtain this end. I use this reasoning only on the supposition that the earth has had a beginning. I am sure I shall read your conjectures on this subject with great pleasure, though I bespeak, beforehand, a right to indulge my natural incredulity and scepticism.