CONSEQUENCES OF THE CONTRACTION 9 



a right angle. The inhabitants copy Alice in Wonder- 

 land; they pull out and shut up like a telescope. 



I do not know of a planet moving at 161,000 miles 

 a second, but I could point to a spiral nebula far away 

 in space which is moving at 1000 miles a second. This 

 may well contain a planet and (speaking unprofession- 

 ally) perhaps I shall not be taking too much licence if 

 I place intelligent beings on it. At 1000 miles a second 

 the contraction is not large enough to be appreciable in 

 ordinary affairs; but it is quite large enough to be appre- 

 ciable in measurements of scientific or even of engi- 

 neering accuracy. One of the most fundamental pro- 

 cedures in physics is to measure lengths with a scale 

 moved about in any way. Imagine the consternation of 

 the physicists on this planet when they learn that they 

 have made a mistake in supposing that their scale is a 

 constant measure of length. What a business to go back 

 over all the experiments ever performed, apply the 

 corrections for orientation of the scale at the time, and 

 then consider de novo the inferences and system of 

 physical laws to be deduced from the amended data ! 

 How thankful our own physicists ought to be that they 

 are not in this runaway nebula but on a decently slow- 

 moving planet like the earth ! 



But stay a moment. Is it so certain that we are on 

 a slow-moving planet? I can imagine the astronomers 

 in that nebula observing far away in space an insignifi- 

 cant star attended by an insignificant planet called 

 Earth. They observe too that it is moving with the 

 huge velocity of 1000 miles a second; because naturally 

 if we see them receding from us at 1000 miles a second 

 they will see us receding from them at 1000 miles a 

 second. "A thousand miles a second!" exclaim the 

 nebular physicists, "How unfortunate for the poor 



