22 THE WORLD MACHINE 



the glowing ball which made their day was three-score million 

 times the bulk of the silver disk which companioned their 

 nights, and four hundred times as far away ? To the eye their 

 diameters are equal ; looked at between thumb and forefinger, 

 held at arm's length, or through a pair of sights set on a board, 

 the angle they subtend is the same. There is nothing to make 

 one think they are so very large, save perchance that they at 

 times seem a good way back of the highest clouds, which in 

 turn may lie far back of towering mountain- tops. Objects at 

 that distance are often larger than they seem ; so Anaxagoras, 

 friend of Pericles, Socrates, Euripides, conjectured that the sun 

 is a body of red-hot iron, and may be as large as the whole of 

 the Peloponnesus that is, half as large as Greece. 



But it is a puzzle to these ancient eyes how these bodies 

 get back again, after setting in the west, to rise once more with 

 the dawn. They must have got round or under in some way ; 

 it is very hard to say. Sometimes they are quite blotted out ; 

 probably the gods are angry or evil spirits are at work, so the 

 multitude will go out from the city and drum valiantly and 

 shout, and drive the spirits away. But when the sun or moon 

 appear again are they the same, or have the gods made new ones ? 

 Even so wise a man as Lucretius, living in the same city beside 

 Caesar and Cicero, is indifferent to which you answer make, if 

 only you leave out the gods and put in their stead Nature, 

 the fecund mother of all, who should be quite equal to the 

 facture of a new luminary once in a while. 



By-and-by, when the shadow cast on the moon by the earth, 

 the slow sinking of the ships below the horizon, the changing 

 elevation of the pole-star as the traveller goes northward or 

 southward, and the arching vault of the heavens have suggested 

 the sphericity of the earth, it seems plausible to suppose that 

 the sun revolves about it, and thus makes night and day. 



Aristarchus of Alexandria, pondering and measuring, con- 

 cludes, eighteen centuries in advance of Coppernicus, that the 

 opposite is true, that the earth sweeps round the sun. But 

 who will believe it, who can imagine it now ? This solid earth, 

 so vast that its curve cannot be measured by the eye, swung 

 free in space, resting on nothing, and booming through the void 

 at the speed of a million and a half miles a day, who can think 

 it ? That is, 66,000 miles an hour, or from Land's End to the 

 Orkneys while the second hand of a watch turns once. A 



