82 FROM NEBULA TO NEBULA 



Nor is it much more difficult to determine the approxi- 

 mate horse-power seconds of energy resident in the moon's 

 6 ' momentum ". Assuming that body to be moving at 

 the exact velocity of 3350 feet a second and that it is fall- 

 ing at the behest of the earth's attraction at the precise 

 rate of one-nineteenth of an inch in the same space of 

 time, we need only divide the fraction into the larger 

 number and multiply the quotient by 240 trillions to get 

 the answer desired. Remember, however, and again I 

 say remember, that, according to Newton's theory, the 

 moon has no way to recuperate lost energy ; hence, when 

 the energy of her momentum Is used up in wrestling 

 against the earth's attraction, that momentum is done 

 for, for good. Now, by the conditions of our problem, 

 the moon's momenta! (inertial) energy is constantly 

 pitted against the earth's attraction, which is always 

 fresh, can never be used up, and is uniformly self -renew- 

 ing. Dividing, therefore, as we did above, 3350 feet, or 

 its equivalent in inches, 40200, by 1-19 we obtain the quan- 

 tity 763,800, which is the number of seconds that it should 

 take the centripetal attraction to wear out the moon's 

 momental energy completely. Eaised to higher terms, 

 this period amounts to 8.8 days, which is reasonably close 

 to the time generally estimated that it would take the 

 moon to fall to the earth if dropped from a state of ab- 

 solute rest. This result agrees well with the rule that 

 "projectiles fired horizontally reach the earth simultane- 

 ously with like objects dropped from the same height." 

 Again, does the moon really fall toward the earth as 

 astronomers allege ? It is admitted, on all hands, that its 

 mean distance is quite, or at least very nearly, the same 

 from month to month and from century to century. If it 

 be correct to say that the moon is falling simply because 

 it is continually diverging from the tangent of its orbit, 

 it is no less correct to assert that the dome on the Capitol 

 at Washington is falling, because it, too, is continually di- 

 verging from the tangent of the circle in which it revolves 

 by reason of the earth's diurnal rotation; specifically, 

 three inches per second. According to the doctrine of 



