ii2 GRAVITATION— THE LAW 



guides the stars in their courses is the same as that 

 which in our common experience causes apples to drop, 

 breaks down because it is our common experience in the 

 lift that apples do not drop. 



I think we have now sufficient evidence to prove that 

 in all other respects the scientific laws determined in 

 the lift will agree with those determined under more 

 orthodox conditions. But for this one omission the men 

 in the lift will derive all the laws of Nature with which 

 w r e are acquainted, and derive them in the same form 

 that we have derived them. Only the force which 

 causes apples to fall is not present in their scheme. 



I am crediting our observers in the lift with the usuai 

 egocentric attitude, viz. the aspect of the world to me 

 is its natural one. It does not strike them as odd to 

 spend their lives falling in a lift; they think it much 

 more odd to be perched on the earth's surface. There- 

 fore although they perhaps have calculated that to beings 

 supported in this strange way apples would seem to 

 have a perplexing habit of falling, they do not take our 

 experience of the ways of apples any more seriously 

 than we have hitherto taken theirs. 



Are we to take their experience seriously? Or to put 

 it another way — What is the comparative importance to 

 be attached to a scheme of natural laws worked out by 

 observers in the falling lift and one worked out by 

 observers on terra ftrmal Is one truer than the other? 

 Is one superior to the other? Clearly the difference if 

 any arises from the fact that the schemes are referred 

 to different frames of space and time. Our frame is a 

 frame in which the solid ground is at rest; similarly their 

 frame is a frame in which their lift is at rest. We have 

 had examples before of observers using different frames, 

 but those frames differed by a uniform velocity. The 



