A NEW PICTURE OF GRAVITATION 117 



The ancients believed that the earth was flat. The 

 small part which they had explored could be represented 

 without serious distortion on a flat map. When new 

 countries were discovered it would be natural to think 

 that they could be added on to the flat map. A familiar 

 example of such a flat map is Mercator's projection, and 

 you will remember that in it the size of Greenland 

 appears absurdly exaggerated. (In other projections 

 directions are badly distorted.) Now those who adhered 

 to the flat-earth theory must suppose that the map gives 

 the true size of Greenland — that the distances shown in 

 the map are the true distances. How then w r ould they 

 explain that travellers in that country reported that the 

 distances seemed to be much shorter than they "really" 

 were ? They would, I suppose, invent a theory that there 

 was a demon living in Greenland who helped travellers 

 on their way. Of course no scientist would use so crude 

 a word; he would invent a Graeco-Latin polysyllable to 

 denote the mysterious agent which made the journeys 

 seem so short; but that is only camouflage. But now 

 suppose the inhabitants of Greenland have developed 

 their own geography. They find that the most important 

 part of the earth's surface (Greenland) can be repre- 

 sented without serious distortion on a flat map. But 

 when they put in distant countries such as Greece the 

 size must be exaggerated; or, as they would put it, there 

 is a demon active in Greece who makes the journeys 

 there seem different from what the flat map clearly 

 shows them to be. The demon is never where you are; 

 it is always the other fellow who is haunted by him. 

 We now understand that the true explanation is that the 

 earth is curved, and the apparent activities of the demon 

 arise from forcing the curved surface into a flat map 

 and so distorting the simplicity of things. 



