Stoney — On Reversal throughout the Universe. 44[> 



To such a spectator the past history of the universe would 

 repeat itself in reverse order, and many of the conditions under 

 which it would do so would appear to him very strange. The 

 "bird which was shot to-day by the sportsman, and which is now 

 lying in his kitchen, will, if the reversal of the universe were to 

 take place at this instant, he restored by the keeper to the game- 

 bag, will be carried by him, walking backwards, to the place 

 where the pointer had fetched it in, where he will take it out, and 

 lay it on the ground. Thence the dog will lift it in his mouth, 

 and, trotting backwards, will reach the spot where the bird fell, 

 where, however, it will now rise to the height at which it was shot, 

 from which it will fly away backwards unharmed. Meanwhile, 

 the vapours into which the powder had been dissipated will stream 

 back into the barrel of the fowling-piece, and condense themselves 

 again into gunpowder, while the grains of shot will rush towards 

 the muzzle of the gun, and crowd into its breach. 



It is of importance to observe that, under the new conditions 

 of the universe, all true dynamical laws will remain the same as at 

 present, but many quasi-dynamical laws will be reversed. Thus, 

 the first law of thermodynamics — the law of the equivalence of 

 energy — will remain unaltered, but the second law will become its 

 converse. Instead of a warmer body tending to impart heat to a 

 cooler body, as at present, the new condition of things will tend to 

 make their temperatures more divergent. Heat will become 

 mechanical energy directly, and without requiring the accom- 

 panying degradation of energy which now takes place. Friction, 

 instead of retarding the progress of bodies, will help them forward. 

 The air, instead of impeding a missile passing through it, will 

 urge it on. And, when reviewing a system so divergent from 

 what we find in the actual universe about us, it is very instructive 

 to bear in mind that the universe, under the new conditions that we 

 suppose, would be as perfect a dynamical system as the actual universe 

 is. This places before the mind in a very strong light the grave 

 error which is too often made when such laws as I have referred 

 to — the second law of thermodynamics, &c. — are supposed to be 

 true dynamical laws. 



This naturally leads up to the consideration whether the laws 

 of causation would be affected. Those relating to true causes 

 would not be affected : those relating to quasi-causes would all be 



2 H2 



