36 FROM NEBULA TO NEBULA 



Newton's theories as they stood then, and, for that mat- 

 ter, still stand. He called attention to the fact that all 

 the planets revolve in nearly the same plane, that they re- 

 volve all in the same sense, that their orbits are almost 

 circular, that the axial rotations of the planets show simi- 

 lar uniformities, that the revolutions of their satellites do 

 so likewise, and that Newton's theories throw no light 

 whatsoever on these significant concordances. Continu- 

 ing, he demonstrated, on the theory of probabilities, that 

 the chances of all these concordances happening together 

 were as one against billions of billions. This, too, before 

 the discovery of Neptune, of all save four asteroids, and 

 of most of the satellites ! To-day the Nebular Hypothe- 

 sis is practically defunct, and nothing has arisen to fill its 

 place but the difficulties Laplace pointed out still are 

 there, and are still clamoring for dynamical explanation. 

 Shall we not judge Newton's system by its negative quali- 

 ties, by its many sins of omission, as well as by its posi- 

 tive merits ? 



If you will tie one end of an elastic string to a small 

 solid ball and, keeping the other end of the string in your 

 hand, whirl the object round and round, you will find the 

 tension on the string increase and the string itself 

 lengthen the faster the whirling is done. Nor can you 

 fail to note that, with each turn, you mechanically execute 

 with your hand a FLINGING MOTION ; stop that and the ball 

 will instantly fly back at you with force. You might, per- 

 haps, suppose that the energy you applied in this way all 

 went toward overcoming the resistance of the atmos- 

 phere, but this is not so, as you may easily prove to your- 

 self by trying the experiment over again with a large 

 holloiv ball of the same weight as the solid one. Let me 

 ask you in all frankness, do you see any analogy between 

 this experiment and the case of the earth and the moon ? 

 The "string" of gravitational attraction is indeed there, 

 but can you point out to me any equivalent action on the 

 part of the earthy any whirling maneuver, that fills the 

 place of the flinging motion of your hand? I know you 

 cannot, nor can the sophisticated astronomers, them- 



