FRAMES OF SPACE 13 



Suppose that we and the nebular physicists survey 

 the world, that is to say we allocate the surrounding 

 objects to their respective positions in space. One 

 party, say the nebular physicists, has a large velocity; 

 their yard-measures will contract and become less than 

 a yard when they measure distances in a certain direc- 

 tion; consequently they will reckon distances in that 

 direction too great. It does not matter whether they 

 use a yard-measure, or a theodolite, or merely judge 

 distances with the eye; all methods of measurement 

 must agree. If motion caused a disagreement of any 

 kind, we should be able to determine the motion by 

 observing the amount of disagreement; but, as we have 

 already seen, both theory and observation indicate that 

 there is complete compensation. If the nebular physi- 

 cists try to construct a square they will construct an 

 oblong. No test can ever reveal to them that it is not a 

 square; the greatest advance they can make is to recog- 

 nise that there are people in another world who have got 

 it into their heads that it is an oblong, and they may be 

 broadminded enough to admit that this point of view, ab- 

 surd as it seems, is really as defensible as their own. It 

 is clear that their whole conception of space is distorted 

 as compared with ours, and ours is distorted as com- 

 pared with theirs. We are regarding the same universe, 

 but we have arranged it in different spaces. The original 

 quarrel as to whether they or we are moving with the 

 speed of 1000 miles a second has made so deep a cleavage 

 between us that we cannot even use the same space. 



Space and time are words conveying more than one 

 meaning. Space is an empty void; or it is such and such 

 a number of inches, acres, pints. Time is an ever-rolling 

 stream; or it is something signalled to us by wireless. 

 The physicist has no use for vague conceptions; he often 



