94 FKOM NEBULA TO NEBULA 



Plainly, the moon instead of dropping to x, therefore, 

 falls to y, and we have a repetition of the condition ex- 

 hibited in Fig. 1, in which it was shown that the velocity 

 of the moon, by the combination of the projectile force 

 with the centripetal attraction, is slowed proportionately 

 to that of an arc as compared with its tangent. That the 

 two forces mentioned do not act cumulatively, but in 

 opposition to each other, resulting in a logical diminution 

 of speed 9 clearly appears from the direction of the line 

 psZ, which depicts the mean direction of the action of the 

 central force, and which visibly intersects the tangent at 

 an acute angle. This loss of velocity, be it noted, is not in 

 any sense attributable to the presence of a resisting 

 medium, but is the inevitable and logical outcome of the 

 principle of central attraction, and calls for the assign- 

 ment of a substantial counteracting centrifugal force. 



Suppose, for the sake of argument, that the moon 

 really did fall acceleratively as Newcomb describes, then 

 at the end of the first quadrant she will have gained a 

 velocity equal to 3350 feet per second in addition to the 

 "persistent" momentum with which she started out. 

 Would not this constitute quite an embarrassment of 

 riches 1 Furthermore, what shall be said of the contradic- 

 tory statements : that the moon only falls two miles dur- 

 ing the entire month ; that she doesn't fall at all, since she 

 perennially preserves her mean altitude; that she falls 

 out to apogee and in to perigee 31,000 miles alternately; 

 and, finally, that she falls not uniformly but accelera- 

 tively? 



Suppose that you were called upon to run a hundred 

 yards against time, starting from scratch and thence to 

 and around a goal post and return ; do you think you could 

 make as good a showing and with no greater expenditure 

 of energy as in a straightaway course of the same length? 

 Of course you could not, nor could you find a normal boy 

 old enough to know what it means to run such a race who 

 would say you could. Astronomers, however, tell us that 

 the moon can! Every month she starts from perigee, 

 courses her way out to apogee, makes a wide detour, and 



