132 



KNOWLEDGE, 



[June, 1903. 



and radiant energy becomes so irregular that life cannot 

 exist. These are pure assumptions, without any scientific 

 ground to sustain tbeni. On the contrary, we see the law 

 of gravitation ruling over the most distant double star 

 systems. We need more than an assumption to over- 

 throw a doctrine so plausible as that of the plurality of 

 inhabited worlds. 



To leave these secondary questions and to examine the 

 ])robk'm itself. Dr. Wallace asserts that, on the authority 

 of the new astronomy, the Sun occupies a special and 

 unique situation, being at the very centre of the universe. 

 i)o the astronomical results justify that very important 

 conclusion ? 



The scientific basis upon which Dr. Wallace mainly, if 

 not entirely relies, is that of the iuvalirable book by Prof. 

 Newcomb, " The Stars : a Study of the Universe." We 

 fear Dr. Wallace did not read this book with suificieut 

 cai-e, for we have just read again that masterly work, and 

 we are \>j no means led to such a conclusion as that 

 reached by Dr. Wallace. 



Jn the first place we are confronted by the question, '" Is 

 the universe finite or infinite?" An insoluble problem 

 in the present state of science. With Newcomli, Dr. 

 Wallace says : " The universe, or, at least, the visible 

 universe seems finite," and he follows the arguments 

 of Prof. Newcomb completely. We believe, personally, 

 that no convincing proof has been brought out against the 

 universe being infinite; Imt, for brevity, we will grant 

 that the visible universe is a limited body. We will also 

 even grant that our solar system lies in the medial plane 

 of the Milky Way (from the fact that the Galaxy is seen 

 on the Heavens as nearly a great circle, which it would 

 not be if we viewed it from a side of the central plane). 

 But this is all ; and we are unable to say with Dr. Wallace 

 that the sun is placed exactly at the centre of the Galactic 

 ring. In fact, no such a definite conclusion is warranted 

 except by evidence which is not yet before us. 



If we grant, however, that the sun is in the neiyhboarhood 

 of the central plane of the Milky Way. does it follow that 

 we are in the centre of the Galactic universe ? It would 

 do so, according to our author ; and to put his theory on 

 tii-m ground, Dr. Wallace again refers to the researches of 

 Pnif. Newcomb and Kapteyn (of Griiningen). Prom their 

 marvellous studies, so clearly set forth by Newcomb in 

 "The Stars," the nearer stars (nearness indicated not by 

 their brilliancy, but by their mean proper motion) would 

 form a sort of solar cluster, almost globular, and the Sun 

 would be deejdy immersed in that cluster. But if w^e 

 suppose these results from somewhat hypothetical stellar 

 statistics to be true, why should Dr. Wallace say our Sun 

 is at the centre of that cluster and, therefore, at the centre 

 of the whole universe ? 



We have ourselves studied the text of Newcomb's work, 

 certtiiuly the scieptific base of Mr. Wallace's paper, and 

 we were quite imable to find any sufficient arguments to 

 establish this central position of our Sun. Pmf. Newcomb 

 writes (p. 312) on the nearness of the Sunto the central 

 plane of the Galaxy. According to Dr. Wallace's theory, 

 (.lur luminary must be at the very centre of the Galaxy, 

 otherwise it would lose immediately its unique situation. 

 Even for Prof. Newcomb, it remains to be proved whether 

 tlie Sun is or is not at the centre of the medial Galactic 

 plane, some facts inducing him to think that we are nearer 

 to one side of the Milky Way (in the constellation Aquila) 

 than to the other. Further, if by hypothesis, at a given 

 instant, the Sun were at the centre of the universe, it 

 would lose its position soon, and never return to it again. 

 We must not forget the proper motion of our luminary, a 

 motion of ten miles per second at least. With that speed. 

 how- could the Sun rest for all eternitv at the centre of the 



universe, as a king on his throne ? We must npt forget 

 also that this solar motion is a relative one, deduced from 

 the apparent opposite motion of the stars. This seems a 

 clear proof that the sidereal universe does not remain 

 concentric (so to speak) with the S\m. 



We have, therefore, no right to claim for the Sun, the 

 Earth, and man, a peculiar and privileged position. We 

 must not indeed neglect on a priori grounds any theory, 

 however startling and unexpected it may be, but we may 

 respectfully invite the new theorist to submit his views to 

 the cross-examination of science. We regret to say that 

 we believe Dr. Wallace's ideas are not supported by the 

 new astronomy. His paper is astonishing and, in a sense, 

 interesting to read, but we very candidly declare ourselves 

 not convinced by the reasons offered to us, and we remain 

 impenitent adherents of the doctrine of the plurality of 

 worlds ; a doctrine so simple, so charming to the human 

 mind, and so fertile in philosophical deductions. 



When we gaze on the heavens, wo prefer to think that 

 there are other lives and other humanities, than to i)lace 

 ourselves on a pedestal and to look proudly round an 

 empty universe. We acknowledge, without hesitation, 

 that this preference is no material proof of life on other 

 worlds, but we beg in exchange to be allowed, without 

 being considered guilty of contempt for the teachings of 

 science, to regard the Sun and the Earth as very ordinary 

 orbs, having no special characteristics, and as no more 

 siutable for life than innumerable other suns and planets 

 which rotate in the unknown infinite. 



Marcel Moye. 

 Professor iti the University of MontiJfllier 

 (France). 



5, rue Flaugergues, 



Montpellier, France. 



IS THE UNIVERSE LIMITED? 



TO THE EDITORS OF KNOWLEDGE, 



Sirs, — In a notice of Dr. A. E. Wallace's recent article 

 by Professor W. H. Pickering, a view of the question of 

 the limits of the universe is taken which I think will 

 strike many of yoiu' readers as new, but seems to be borne 

 out to a considerable extent by the Harvard observations 

 on the stars in the constellation of Orion. It is that an 

 infinite numlier of luminous stars is quite consistent with 

 the limited quantity of light which we receive from the sky, 

 provided that the distance between the stars becomes (on 

 the average) greater the farther we go from the solar 

 system. On the generally accepted scale, the light of a 

 star of the ?i'* magnitude exceeds that of a star of the 

 n + 1"' magnitude in the proj)ortion of 2'512 to 1. Now 

 suppose the average distances of the stars in question to 

 be in the ratio of 1'585 (= f^ '2-512) to 1, and that owing 

 to the thinning out of the stars the number only increases 

 in the ratio of l-25(> for each degree of magnitude. The 

 total light of the stars of the n + 1"' magnitude would 

 then Ije only one-half of that of the stars of the «"' magni- 

 tude ; and if the same process went on to infinity, the 

 total light of all the stars fainter than the «'* magnitude 

 would only be equal to that of stars of the »i'* magnitude. 



Taking the constellation of Orion, the increase in the 

 number of stars for each magnitude has, according to the 

 Harvard observations, come down to 14 or 13 to 1 before 

 the stars become too faint for measurement. If this 

 proportion continued to infinity the total light would be 

 of very limited amount. The number of stars would 

 indeed be infinite, for the number of the n -f i"'magnitiide 

 would always exceed that of the n"', but the total light 

 given would diminish rapidly as n increased, and even if 



