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♦ KNOWLEDGE ♦ 



[March 1, 1888. 



accomplished, it became possible to foi-m a clear idea of the 

 relative distances and even some idea of the actual distances 

 of the other planets, and thus to form adequate ideas of the 

 relative importance of those orbs as compared among them- 

 selves, and even as compared with the eai'th. The addition 

 to the universe of five other worlds, probably at least as 

 large (on the average) as the earth, was assui'edly a most 

 striking achievement. No wonder if the more narrow- 

 minded among religionists, unable to reconcile such a dis- 

 covery with the limited ideas they had formed of the might 

 and wisdom of the Deity, shuddered with horror at the 

 daring of the Copernicans in imagining (nay, in even 

 venturing to prove), that there may be other worlds than 

 ours. 



Even this, however, was in turn but nothing when com- 

 pared with the discovery of the real meaning of the stars, 

 following almost immediately on the recognition of the real 

 nature of the planets. Tycho Brahe, who was moved with 

 something like indignation against the doctrines of Coper- 

 nicus, pointed out at once that if they were true every star 

 must be an orb of enormous size and splendour, perhaps 

 comparable even with the sun, which he regarded as 

 preposterous. For, said he, our earth could not circuit 

 in this immense orbit which the fond Copernicans as- 

 sign to her, without causing the constellations to change 

 entirely in aspect in the course of each year. In autumn or 

 winter, for instance, we look at the constellation Orion from 

 a position many millions of miles away from that which we 

 occupy when we look at that constellation in spring. Hence 

 the star groupings would present an entirely altered appear- 

 ance, unless we are to imagine that such a distance as 

 100,000,000 of miles (the real distance is 18(5,000,000 of 

 miles, but Tycho Brahe did not know that) counts for 

 nothing as compared with the distances of the stars. But 

 if so, if they really lie at distances which must be measured 

 by thousands of millions of miles, we need only remember 

 that our sun removed to such distances would look no 

 larger than a star, to see that we must regard the stars, 

 manifestly self-luminous as they are, as veritable suns, if 

 this pernicious Copernican theory is admitted. 



When Kepler and Newton had established the Copernican 

 theory on altogether irrefragable evidence, and when the 

 telescope enabled men to measure the planets, still grander 

 ideas about the universe began to force their way into men's 

 minds. It was seen that Jupiter and Saturn are very much 

 larger than the earth, and are the centres of systems of 

 subordinate worlds. With increasing accuracy in the 

 estimates of the sun's distance, it was seen that all the 

 planets are farther off, and therefore larger than had been 

 supposed. It became, in fine, certain that the earth is not 

 the chief member of the family of worlds attending ujion 

 the sun. 



But this was nothing compared with the amazing sig- 

 nificance of the self-same telescopic teachings in regard to 

 the stars. Not only did every increase in the estimate of 

 the sun's distance increase in corresponding degree men's 

 estimate of the stars' distances, but every increase in the 

 power of estimating position made clearer and clearer the 

 apparent fixity of the stars, and therefore threw them, as it 

 were, farther and farther back into the abysses of space. 

 It had been wonderful enough that the eye could detect no 

 relative displacements among the stars as the earth circled 

 in her wide orbit around the sun. But it presently became 

 clear that, even with the immense increase in the power of 

 determining positions which the telescope gave to astrono- 

 mers, no sign of change could be detected during the year 

 in the position of any star. Bradley attacked the problem, 

 but though he worked so well that he was able to detect 

 the annual change due to the aberration of light and the 



nutation (or nodding motion) of the earth's axis, he dis- 

 covered no annual displacement. The best astronomers 

 in Great Britain and on the Continent attempted the 

 task and failed. At length astronomers gave up hope, 

 beginning to regard the stars as, all and severally, too 

 far removed to afford appreciable evidence of displacement 

 as the earth revolved in her wide orbit around the sun. 



But just when success was despaired of, a double success 

 was secured. Henderson, at the Cape of Good Hope, 

 recognised the measurable annual displacement of the bright 

 star Alpha Centauri ; while Bessel, at Konigsberg, recog- 

 nised a smaller yet measurable displacement of the faint 

 star (barely visible to the naked eye) numbered 61 in 

 the constellation of the Swan. (Bessel had chosen this 

 faint star for observation because it is moving much more 

 rapidly on the star sphere than its fellows, as if it were rela- 

 tively near the earth, so that its motion, though not really 

 greater than that of other stars, appeared greater through 

 the effects of proximit}'.) But when at last the problem 

 had been mastered, when for the first time the actual dis- 

 tances separating us from the stars, and the stars from each 

 other, came to be recognised, how tremendous those dis- 

 tances were found to be ! The nearest of all the stars in 

 the heavens lies twenty millions of millions of miles from 

 us, in such sort that light speeding with a velocity of 

 187,000 miles in a second takes more than three years in 

 coming to us from that star. Our sun removed to the same 

 distance would appear but as a star — nay, he would be a 

 very much smaller star, in appearance, than that nearest of 

 all our neighbouring suns. 



But in the meantime, while one set of astronomical 

 researches was showing astronomers the immensity of 

 stellar distances and the sunlike character of every star, 

 another set of researches had shown and was showing the 

 vastness of the numbers of the suns within our galaxy. The 

 thousands of suns visible to the naked eye had increased 

 to hundreds of thousands in the days even of Galileo. 

 Another century had shown astronomers that the stars 

 within telescopic range must be counted by millions. Sir 

 William Herschel's gauges of the star depths had shown 

 that our estimate of the numbers of the stars must run 

 into tens and even hundreds of millions. And to-day, it is 

 well known that if the most powerful of the telescopes made 

 by man could be used in surveying every portion of the 

 heavens, the total number of stars which would be brought 

 into view would far exceed one thousand millions. The 

 increase with each increase of telescopic power has, more- 

 over, taught the lesson that we can in no sense limit our 

 estimate of the number of stars by the number which even 

 our most powerful telescopes would show. If we could 

 double the space-penetrating power of our telescopes, we 

 should probably much more than double, we should 

 increase manifold, the number of stars — that is, of 

 suns — which would be brought within our ken. Not 

 thousands of millions, but probably millions of millions of 

 suns exist within the limits of the sidereal system. Bather 

 — I ought to say — they exist within the limits of our 

 sidereal system, for doubtless this system is no more to be 

 regarded as single within the viniverse than our solar system 

 is unique within the star depths. Every star tells us of a 

 sun. and probably of a solar system, in such sort that we 

 must recognise thousands of milHons of solar systems in the 

 galaxy. May we not fairly assume, then, that in like 

 manner our sidereal system is repeated millions of millions 

 of times within some systena of a higher order. That 

 system may be in turn repeated many millions of times 

 within a system of a higher order. And so on, to higher, 

 and higher orders, absolutely without end. 



Recognising this as the teaching of the astronomy of to- 



