ORIGIN OF THE WORLD 



same axis and with a good deal the same speed that 

 it had before the explosive outburst occurred which 

 produced the spiral nebula out of which the planets 

 have developed. 



The planets themselves, as they were built up about 

 nuclei or masses in the spiral nebula, might at first 

 have no motion of rotation, but would begin to rotate 

 in response to the influence of impinging planetesi- 

 mals. 



Professor Moulton shows that the results of such 

 impingement would be generally, but not necessarily, 

 to give a forward rotation somewhat in the plane of 

 revolution. But the presence of other large masses 

 (future moons) near by may alter this; and there is 

 no theoretical reason why any degree of aberration 

 might not be observed. Thus the variously tipped 

 axes of the planets are accounted for. 



Again, outlying masses that were not at first part 

 of a given planetary system might be brought within 

 the influence of a forming planet at a relatively late 

 stage (somewhat as Jupiter even now captures 

 comets), and these captives might revolve in any 

 plane or in any direction, just as comets do. So the 

 retrograde revolution of Phoebe is explained; also 

 the aberrent revolution of the moons of Uranus and 

 Saturn. Likewise the speed of little Phobos, which 

 races three times round Mars while that planet is re- 

 volving once. There is no restriction put upon the 

 speed of a satellite by the rotation speed of its pri- 

 mary according to the new theory. 



It may be added that Professor See of the Marine 

 Observatory at Mare Island, California, has elaborat- 



'5 



