ii6 SCIENCE AND IMMORTALITY 



force the planets which had formed peripherally by- 

 fortuitous accretion of clashing atoms. 



Kant's mechanics were at fault in various respects. 

 Particles falling centrally by gravitative attraction 

 would never cause rotatory movement ; and if 

 rotatory movement did occur, and if the planets 

 formed by accretion were thrown off, they would 

 rotate in exactly the opposite direction to that in 

 which the planets do rotate. These flaws are 

 fatal to his theory, but it was a brilliant attempt at 

 cosmogony. 



Equally brilliant and more correct was Kant's 

 discovery of the cosmogonical fact that the tidal 

 friction between the earth and the moon must retard 

 the motion both of the moon and of the earth. 



It is interesting to know that Kant was inspired 

 in his brilliant speculations by a summary in a 

 Hamburg paper of a" New Theory of the Universe" 

 by one Thomas Wright, son of a Durham carpenter. 



In 1796 Pierre Simon Laplace brought forward 

 his famous nebular hypothesis of a fire-mist which 

 once stretched from the centre of the sun to at 

 least as far as the outermost planet of our system, 

 and which, as it cooled and contracted, threw off 

 the planets as nebulous equatorial rings (such as 

 are still seen in Saturn's Belt), which rings, again, 

 eventually coalesced into globular masses and 

 formed planets. According to a well-known law 



