108 FROM NEBULA TO NEBULA 



round, or that the storage battery of the axial momentum 

 of the earth is losing 700 quadrillions of horse-power 

 right along. If the former be the case, what is that 

 power? If the latter, how long can the earth's momen- 

 tum hold out, and why doesn't the rotation slow down, 

 even a little bit ? 



Again, accepting Sir Robert Ball as spokesman for 

 his fellow astronomers to the effect that the energy that 

 produces the tides emanates not from the sun or moon, 

 but out of the earth's store of centrifugal momentum, let 

 us see what this, also, amounts to. Flammarion gives the 

 sum of the lunar and solar tides as (approximately) 30 

 inches at the equator. Taking their average height for 

 the whole world as 15 inches, and limiting this again to 

 only half the ocean surface (75,000,000 miles), gives a 

 weight of water thus alleged to be perpetually whirled 

 upward by the earth of, in round numbers, 80 trillions of 

 tons. As this action is going on all the time, it means 

 that, on this second count, the centrifugal force is wasting 

 away at the steady gait of 80 trillions of horse-power. 



The complacent reader may think to himself that, 

 huge as these drains upon the rotational energy of the 

 earth seem to be, they must, nevertheless, be negligible 

 in comparison with their source, else our Newtonian 

 friends would not dare to draw upon that source so ex- 

 travagantly as they do. Now, it is easily possible to as- 

 certain the magnitude of this supply in terms of horse- 

 power within reasonable limits of accuracy. Assuming 

 that one-half of the earth's mass is contained within an 

 inner core 6,000 miles in diameter, and that the average 

 velocity of the whole mass is the same as the velocity of 

 any point on the equator of that core, the distance cov- 

 ered in a single second would be 1160 feet. This is mani- 

 festly an overestimate, seeing that, in the higher lati- 

 tudes, the velocity is necessarily much less, and, for con- 

 venience, we may arbitrarily reduce this quantity to 1116 

 feet per second, which, though still too high, happens to 

 be one-third of the orbital velocity of the moon and there- 

 fore simplifies the present calculation by furnishing us 

 with a convenient standard for comparison. 



