220 



KNOWLEDGE. 



[October, 1908. 



to contain helium, it is possible that these are radio-active 

 also, and to this their efficacy may be due. It is generally 

 understood that the Bath waters lose their efficacy if not 

 taken immediately after being drawn, and this may be 

 due to the decomposition of the small trace of radio-active 

 substance which they presumably contain. 



MAN'S PLACE IN THE UNIVERSE. 



By E. Walter Maunder, f.r.a.s. 



In the Fortnightly Rei-ieir for September, 1903, Dr. Alfred 

 Kussel Wallace replies to the critics of his paper on 

 " Man's Place in the Universe." The critics had attacked 

 each and every astronomical point of his position, and 

 now, in his reply. Dr. Wallace withdraws most of his 

 astronomical arguments, whilst re-asserting the conclusions 

 which he had drawn from them. His reply, therefore, 

 though in form a defence of his original position, is in 

 substance an unconditional surrender of it. 



It may be well to quote here Dr. Wallace's summary 

 and conclusion of his first paper : — 



" We caa hardly suppose any longer that three such remarkable 

 coincidences of position and consequent physical conditions should 

 occur in the case of the one planet, on which organic life has been 

 developed, without any causal connection with that development. 

 The three startling facts— that we are in the centre of a cluster of 

 Buns, and that that cluster is situated not only precisely in the 

 plane of tlie Galaxy, but also centrally in that plane, can hardly 

 now be looted upon as chance coincidences without any significance 

 in relation to the culminating fact that the planet so situated has 

 developed humanity. 



" Of course the relation here pointed out may be a true relation 

 of cause and effect, and yet have arisen as the result of one in a 

 thousand million chances occurring during almost infinite time. 

 But, on tlie other hand, those thinkers may be right, who, holding 

 that the universe is a manifestation of Mind, and that the orderly 

 development of Living Souls supplies an adequate reason why such 

 an universe should have been caUed into existence, believe that we 

 ourselves are its sole and sufficient result, and that nowhere else 

 than near the central position in the universe which we occupy, 

 could that result have been attained." 



Now if we assume that these words imply what their 

 sense may be taken to indicate, we infer that Dr. Wallace 

 means that: — 



(1) Tlie Galaxy with its appendages and included 

 systems, to all intents and purposes makes up the 

 entire material universe. 



(2) The earth in its character of a satellite of the sun 

 is situated centrally in the plane of thu Galactic 

 ring, and the physical conditions necessary to 

 life are only possible in such a central position. 



On the first point Dr. Wallace's withdrawal from his 

 former position is sufficiently definite. He writes : — 



" Is the evidence at our command for or against the infinite ex- 

 tension of the stellar universe ? This is the real question, the only 

 question we are able to discuss rationally. As to proof or disproof, 

 either is impossible as regards what exists, or what does not exist in 

 infinite space. And even as regards the probability of any parti- 

 cular form of existence being infinite, we have, and can have, no 

 evidence, and without evidence it is irrational to hold any definite 

 opinion." 



With this position astronomers cannot quarrel ; it is 

 indeed the very point for which Dr. Wallace's critics were 

 contending. But it cuts away the ground from the argu- 

 ments of his first paper ; he then claimed to have 

 demonstrated that which he now admits to be incapable of 

 proof. It is true that in the next sentence he re-asserts 

 his claim to have brought forward " sufficient evidence " 

 of the limitation of our stellar universe, but before the end 

 of the next paragraph he seems to have come to the con- 

 clusion that since his position cannot be demonstrated, it 

 ought not to be challenged, and he refers to objections as 

 " the opinions or prejudices of those who ask for proofs 



of what cannot be proved." Dr. Wallace makes several 

 quotations to show that astronomers of repute have arrived 

 at the conclusion that the stellar universe is limited in 

 extent, and complains that directly he, an outsider, 

 ventures to set forth the same view, he is found fault 

 with. 



There has been no dead set made upon Dr. Wallace 

 because he is an outsider. Some three years before the 

 appearance of his first paper in the Fortnightly Revieiv 

 there was an interesting discussion in Knowledge on the 

 question "Is the stellar universe finite?" which I concluded 

 by the following words : — 



" The general question * Is the Stellar Universe finite ? * becomes 

 at once not a pliysical but a metaphysical enquiry, and hence leaves 

 the domain of astronomy, and except as a purely mental exercise I 

 see no value in it. How easily even the keenest and most trained 

 minds may go astray on the subject may be learned from Prof. 

 Newcomb's paper in the March number of the Windsor Magazine* 

 He writes ' it can be shown mathematically that an infinitely ex- 

 tended system of stars would fill the heavens with a blaze of light 

 like that of the noonday sun.' There is a tacit assumption here that 

 the stars are on the average uniformly distributed in space, an 

 assumption which for nearly a century astronomers liave known to be 

 untrue. "t 



A similar statement by Prof. Newcomb occurring in 

 a paper in the Popular Science Monthly appears to have 

 been the basis of Dr. Wallace's original paper, but that it 

 was a mistake, and that Prof. Newcomb did not alter his 

 views merely in order to disagree from Dr. Wallace, may 

 readily be seen by referring to the same paper when it was 

 corrected and republished in book form in 1901. 



Dr. Wallace yet more unreservedly withdraws his 

 suggestion that the suns on the confines of the Milky Way 

 aiv " becoming dissipated into outer space," and that "the 

 outer margins of the stellar universe are therefore unstable," 

 so that it " follows that the outer portions of the universe, 

 at all events, and for an unknown extent inward, will be 

 entirely unfitted to ensure that continuity of uniform 

 conditions which is the first essential for the development 

 of life." He now admits " that there is probably no 

 justification for this idea, and that the facts that suggested 

 it are apparent only." He also withdraws the " similar 

 unfounded notion ... of a variation of gravity near the 

 boundary of the universe." But these two " unfounded 

 notions " were his sole arguments to prove that " the 

 continuity of uniform conditions which is the first essential 

 for the development of life " is not possible in the case of 

 satellites of such suns as lie within or on the confines of 

 the ring of the Galaxy. There is left, therefore, not even 

 a suggestion of a reason for supposing any star within the 

 reach of our telescopes to be less stable in the conditions 

 due to its position than is the case with our sun. 



These ample concessions having been made, it would be 

 a superfluous task to show again that Dr. Wallace had no 

 solid grounds for asserting the ceutrality of our sun in his 

 particular sense of the word. He complains that his critics 

 misrepresent him on this point, and ascribe to him a 

 precision of meaning which he did not intend. He prefers 

 now to speak of the position of the sun as " nearly 

 central." Frankly, I think his critics allowed his ex- 

 pressions to pass as being less stringent than they 

 were. But a turn of expression may pass for little; it is 

 the argument that counts. And the argument demanded 

 that the sun should be shown to be very materially nearer 

 the centre of the universe than any other star whatsoever. 

 There are no facts known to astronomers which would 

 warrant them in asserting that our sun is better placed in 

 this sense than are hundreds of members of that 

 hypothetical globular cluster of which he speaks. 



• March, 1900. 



t Knowlebok, 1900, May, p. 109, 



