October 2, 1 »*P8 "I 



KNOWLEDGE 



197 



but up which men used to climb ; and everywhere we come 

 across legends of trees rooted in the earth with branches 

 reaching to the sky, or of trees rooted in the sky with 

 branches stretching downwards to the earth. 



In the sky are land and sea, with people, houses and 

 plantations, but most often it is the dwelling-place of 

 heroes and deities alone. 



In Paraguay the souls of the dead go up to heaven by 

 the tree I,l(i<i<U(jna, which joins the earth and sky, and there 

 are myths that tell of a rope let down to earth whereby 

 intercourse is kept up with the sky. Such a story is told 

 in Vancouver's Island ; and in the White Nile district it is 

 said that God made all men good and they lived with Him 

 in heaven, but as some of them turned bad He let them down 

 by a rope to the earth. The good could chmb up again 

 by this rope to the sky, where there was dancing and beer 

 and all was joyous, but the rope broke (or a bird bit it 

 through), so there is no going up to heaven now ; it is 

 closed to men. 



But if we turn to science, how different is the story that 

 we have lo tell ! It is like the old myths of heaven-raising 

 that tell how once the sky fell down so low that men could 

 not stand upright, and then a hero came, who, for a drink 

 of water, raised the sky and pushed it up and up to the 

 place where we see it now. 



For us science is the hero who has raised the heaven, 

 that has examined far-off worlds, that has explored the sky 

 depths, and has stories to tell more marvellous and more 

 romantic than the myths of old. 



It has to tell us that the earth is far larger than men 

 used to think, though the true size of the earth has been 

 approximately known for centuries, and yet it has to tell 

 us also that the place of the earth in space and time is one 

 of inconceivable insignificance. But first think of the 

 greatness of our world. It is a globe nearly eight thousand 

 miles in diameter, but only by putting figures into other 

 shapes and forms do we begin to see their meaning. 



This globe contams two hundred and sixty thousand 

 million cubic miles, and could we load a train with it the 

 length of the train (if the inside of the trucks were six 

 feet wide and six feet high) would be over two lumdred 

 thousand billion miles, and travelling at the rate of sixty 

 miles an hour it would take over three thousand eight 

 hundred and thirty-eight million centuries to pass a given 

 point, while if the engine-driver could communicate with 

 the rear- guard by means of flashes of light it would be 

 thirty-fom- thousand years before the guard saw the signal ; 

 while if we form the earth into a square column reaching 

 to the smi, a distance of ninety-three million miles, each 

 side of the column would be over fifty miles in length. 

 Yet vast as these figures seem, they fade into insignificance 

 by comparison with the sun, for if it were formed into a 

 square column reaching to the earth each side of the 

 column would measure sixty thousand miles, or eleven 

 hundred times as much as the earth column ; put in other 

 words, the sun would provide one milUon three hundred 

 thousand such columns as the earth would make.* 



Even if we keep within the Umits of our solar system, 

 we have distances much more vast than that from sun to 

 earth. 



If we stretch cm- columns until they reach from the 

 sun to Jupiter, the earth-column shrinks to twenty-three 

 miles square, the sun-column to twenty-six and a half 

 thousand ; while reaching out to Neptune, the most 

 distant of the planets, the column formed by the earth 



* The earth is about four times as dense as the sun, and if the 

 columns of matter were of the same density the sim would only make 

 three hundred and thirty-two thousand columns such as the earth 

 would make. 



would be less than ten miles square and the sun eleven 

 thousand, while their length has grown to twenty-eight 

 million centuries of miles. 



How curious a contrast even this affords to more 

 primitive conceptions of the sky, such as that of the 

 Samoans, who think the heavens are at the horizon, or 

 that strangers that come to them, as the white men did, 

 come from beyond the sky and are therefore Paimliiniji, or 

 heaven-bursters. 



The heaven for them has windows or holes where the 

 rain comes through, and if you climb high enough you 

 can look through and see the sky folk living much as 

 men do on the earth. And the Waraus say that there 

 was once a rope by which people used to climb down to 

 the earth through a hole in the sky, until one day a fat 

 man stuck in the hole and people now can neither get up 

 nor down. 



Of men beyond the arch of heaven science knows nothing, 

 but it can say something in regard to the possibility or 

 otherwise of life such as we know it here on other planets, 

 because it can tell something of their temperature, atmos- 

 phere and other conditions ; but as to life in other suns 

 or stars, science for the most part has no word to say 

 and leaves us to guess, like Samoans and more primitive 

 folk. 



As to other worlds scattered through the sky depths, 

 science has lately been learning much ; something of their 

 nature, their number, their distance is constantly being 

 learnt, while the way is being prepared for gaining some 

 real insight into the relations of the stars among them- 

 selves, and for fixing our own position in regard to other 

 suns and systems than our own. 



To Epicurus the stars were little concave mirrors fixed 

 in the firmament and reflecting sunlight ; to the Venerable 

 Bede they were faintly luminous, needing reinforcement 

 from the sun to make them visible. Even to Tycho Brahe 

 there was no great distance between the planets and the 

 stars, and he calculates their distance at fifty to sixty 

 thousand miles. 



But we have to invent a new measure for talking of 

 their distance, since, finding miles too small, we talk of 

 "light years," which means the distance that a ray of 

 light travelling some hundred and eighty-six thousand 

 miles a second would traverse in a year. 



Before we get too used to talking of light years it may 

 be well to try to get a notion what a light year really is. 

 It means a journey that would take an express train more 

 than eleven million years. It means a velocity that the 

 periphery of a gigantic fly-wheel one hundred miles in 

 diameter could not keep up with, though it made five 

 hundred revolutions in a second. It means a distance 

 traversed in one second that sound will not pass over in 

 ten days. 



And this is the ujnit for the quantities that modern 

 astronomy deals with when treating of the distribution of 

 stars in space. Sometimes one hears a cubic light year 

 spoken of — that is, an imaginary cube with each side a 

 light year long. 



It was long after men saw how to measure the distance 

 of the stars before they succeeded so as to feel much 

 confidence in the results obtained ; but now the distances 

 of a few stars are known with comparative accuracy 

 and certainty, many measures having been made that 

 probably come within twenty or thirty per cent, of the 

 truth. 



The nearest star that has been found is Alpha Ceutauri, 

 with a distance of 4i light years. Probably next in order 

 is a small star, numbered 21,185 in Lalande's catalogue. 

 It is about 6i light years off, while 61 Cygni, the most 



