WCP6889

[1]

Parkstone, Dorset

Nov^r 12th 1900.

Rev^d Dr Fisher

Dear Mr Fisher

I am writing to you to ask you to enlighten my ignorance on a physico-mathematical question on which I am trying to form a correct opinion — that of the ^old nebular hypothesis, as compared with the meteorite hypothesis advocated by Lockyer and others, & which seems to me the more in accordance with facts, & the more intelligible. I cannot find any clear statement of the difficulties in the way of the old theory, yet they seem to me to be overwhelming. In the newest book I have — the Concise Knowledge Library on Astronomy — Miss Clerke at p. 235, gives a few [2] objections ^{to it} but chiefly as regards the formation, first of rings, & then of planets or satellites by the breaking up & consolidation of these rings.

But there seem to me to be much more fundamental difficulties. To begin with,— the supposition of the whole matter of the solar system having a formed a gaseous sphere enclosing the orbit of Neptune, and therefore every where of a temperature ^{even at the outer portions} above that of the electric arc, is all together inconceivable, and I think, impossible.

1. We know of no other sources of heat for such a mass, but collisions, or condensation from gravity; and this presupposes enormous aggregations of matter at stellar distances coming into actual collision at high velocities.

But does not the phenomenon of new stars suddenly blazing out & rapidly becoming dark again [3] show that such collisions would not produce permanent gaseous globes very slowly contracting & losing heat, while all the more permanent stars and nebulae give indications of solid as well as gaseous components.

2. But the difficulty becomes much greater when we consider the extreme tenuity of a gaseous mass ^{extending to, and} including Neptune. In a lecture by Sir Rob^t Ball recently, he stated, that even when ^{the nebula} had shrunk to the size of the earth's orbit, it was far less dense than the residual air in one of Crookes' radiometers!

Now my great difficulty is, how the whole solid matter of the earth could be retained for an instant in a gaseous state, when exposed the cold of stellar space.

Supposing it possible that all the iron and other refractory elements could ever had existed in such a [4]¹ condition of extreme gaseous tenuity, would not the radiation of heat into outer space cause rapid condensation in solid metallic particles, or into the various earths and other compounds by chemical affinity, so that there would result an outer shell of solid matter in molecules or cosmic dust, just such as we find to prevade the solar system now, in its meteor ringsm and the stellar spaces in its spiral & ring nebulae.

3. Again, the only ^other rings we find still existing in the solar system — those of Saturn — are meteoritic rings, though of wonderful regularity, not showing any signs of breaking up, or being condensed into satellites.

I have been reading Lockyer's last book on "Inorganic Evolution" — one of the worst-written books I ever read and the hardest to understand though full of valuable facts, — [5]² and the results of all the my recent study of the new astronomy, as I can understand it, is, to show that throughout space matter exists everywhere in all three states, solid liquid & gaseous; while, as we know that at zero temperature all matter would be solid,— that it can only be maintained in either of the other states by heat, that we know no other sources of heat than collisions or condensations due to gravitation; therefore it seems more rational to consider the primitive form of matter to be solid molecules, which coming together by gravitation slowly assumed the liquid or gaseous forms. And if we suppose their distribution [6]³ particles following their own orbits as do the particles that constitute Saturn's rings or those of the great ^solar ring of the asteroids.

This is a very rude & sketchy statement of my difficulties. Do not trouble to reply in any detail, but let me know if you can, where I am wrong, and which of my difficulties — if any — are real ones.

Believe me | yours very truly | Alfred R. Wallace [signature]

P. S. I write to you rather than to Darwin or Sir R. Ball, because you have more leisure, and are probably less prejudiced against an ignorant outsider like myself.

A. R. W.