ATTEMPTS TO EXPLAIN GRAVITATION 255 



One familiar with modern electrical theories knows that the present 

 tendency is to include everything in the electromagnetic scheme. Max- 

 well started this when he promulgated the electromagnetic theory of 

 light. Experiment by Kauffman on the beta rays of radium lead us to 

 regard mass as electromagnetic. Hence it is very natural to try to 

 explain gravitation as an ether-phenomenon. This would require that 

 the ether be capable of supporting enormous pressure or tension. In 

 the older views the ether was regarded as a very attenuated medium. 

 Such an ether can hardly meet the demands. Many modern physicists 

 regard the ether as very rigid and dense when compared with ordinary 

 matter. See Lodge's " The Ether of Space." If we follow Sir J. J. 

 Thomson, who regards all mass as mass of the ether/ we can calculate 

 the density of the ether, for the mass of an electron is about 10 _2T 

 grams and the volume is of the order of 10 -39 cubic centimeters ; hence 

 the density of the ether is 10 12 or a million million times that of water. 

 When we consider the rapidity with which an ether disturbance is trans- 

 mitted we see that the rigidity should be very great compared with 

 ordinary matter. Taking the density of ether as 10 12 and the velocity 

 of ether waves as 3 X 10 10 cms. per sec. the rigidity will be of the 



order of 10 33 dynes per sq. cm., since velocity = a /— = — -nz~"- The in- 

 trinsic energy if due to rotational motion will be of the order of 10 32 

 ergs per cubic centimeter, if we assume the velocity of rotation is of the 

 order of that of light ; since the energy = J mass times velocity 2 , where 

 the mass of a cubic centimeter is 10 12 grams and the velocity is 3 X 10 10 

 cms. per sec. Hence the intrinsic energy and rigidity of the ether will 

 probably meet the demands if we accept the views of ether and matter 

 held by some of the greatest modern physicists. 



If a falling body does not gather its energy from the ether where 

 does it get it? Lift a ton to the height of 1,000 feet above the earth's 

 surface and we have 2,000,000 foot-pounds of potential energy, or pref- 

 erably a body that in returning to its original position will gather 

 2,000,000 foot-pounds of energy. Is this energy inherent in the body ? 

 Newton's letter to Bentley shows us that he was opposed to such a view. 

 One thing is sure, there is no perceptible change in the mass and chem- 

 ical composition of the body at the height of a thousand feet. 



In the " Principia " Newton makes no attempt to explain gravita- 

 tion, but in one of his optical queries he writes thus : " If the pressure 

 in the medium is less in the neighborhood of dense bodies than at a 

 greater distance from them, dense bodies will be drawn toward each 

 other, obeying the law of gravitation if diminution of pressure is 

 inversely as the distance." 



Hooke, a contemporary of Newton and a man of great ingenuity, 



1 See Silliman, "Lectures," p. 51. 



