Foundations of the Universe 267 



million years, and the total age of the earth to some small multi- 

 ple of that. The earth, he considers, is not cooling, but "contains 

 an internal source of heat from the disintegration of uranium 

 in the outer crust." On the whole the estimate obtained would 

 seem to be in agreement with the geological estimates. The ques- 

 tion, of course, cannot, in the present state of our knowledge, be 

 settled within fixed limits that meet with general agreement. 



As we have said, there are other fundamental existences 

 which give rise to more complex problems. The three great fun- 

 damental entities in the physical universe are matter, ether, and 

 energy; so far as we know, outside these there is nothing. We 

 have dealt with matter, there remain ether and energy. We shall 

 see that just as no particle of matter, however small, may be 

 created or destroyed, and just as there is no such thing as empty 

 space ether pervades everything so there is no such thing as 

 rest. Every particle that goes to make up our solid earth is in 

 a state of perpetual unremitting vibration; energy "is the uni- 

 versal commodity on which all life depends." Separate and dis- 

 tinct as these three fundamental entities matter, ether, and 

 energy may appear, it may be that, after all, they are only 

 different and mysterious phases of an essential "oneness" of the 

 universe. 



9 

 The Future 



Let us, in concluding this chapter, give just one illustration 

 of the way in which all this new knowledge may prove to be as 

 valuable practically as it is wonderful intellectually. We saw 

 that electrons are shot out of atoms at a speed that may approach 

 160,000 miles a second. Sir Oliver Lodge has written recently that 

 a seventieth of a grain of radium discharges, at a speed a thou- 

 sand times that of a rifle bullet, thirty million electrons a second. 

 Professor Le Bon has calculated that it would take 1,340,000 

 barrels of powder to give a bullet the speed of one of these elec- 

 trons. He shows that the smallest French copper coin smaller 



