LIGHT AND THE QUANTUM 125 



bizarre as it still seems to the layman, has now 

 been accepted into orthodox physics. 



We may suppose that some years hence a few 

 daring spirits looking for more worlds to con- 

 quer, will build a rocket-like machine, propelled 

 by the expulsion of high-speed particles, and 

 steered by directing the stream of particles one 

 way or another. As their machine becomes per- 

 fected the inventors will find that they are able 

 to leave the earth's atmosphere and visit the 

 moon and nearer planets. In the meantime there 

 is discovered a new kind of "fuel" which emits 

 particles of far greater speed than any known 

 before, so that one bold inventor believes that 

 if he takes a quantity of fuel large compared 

 with the bulk of his machine he may be carried 

 far beyond the bounds of the solar system. 



He makes the attempt, and by using the 

 greater part of his fuel in one initial spurt he 

 attains a speed within one-half of one per cent 

 of the velocity of light. I shall not attempt to 

 describe his sensations during this interval, but 

 after he recovers and shuts off his accelerator he 

 finds the most surprising change in the appear- 

 ance of the heavens. From the rear window 

 everything has disappeared, even the sun which 

 near the beginning of the acceleration still 



