SOME UNSOLVED SCIENTIFIC PROBLEMS 

 ii 



PHYSICAL PROBLEMS 



In regard to all these cosmic and telluric problems, 

 it will be seen, there is always the same appeal to one 

 central rule of action the law of gravitation. When 

 we turn from macrocosm to microcosm it would appear 

 as if new forces of interaction were introduced in the 

 powers of cohesion and of chemical action of molecules 

 and atoms. But Lord Kelvin has argued that it is pos- 

 sible to form such a conception of the forms and space 

 relations of the ultimate particles of matter that their 

 mutual attractions may be explained by invoking that 

 same law of gravitation which holds the stars and plan- 

 ets in their course. What, then, is this all-compassing 

 power of gravitation which occupies so central a position 

 in the scheme of mechanical things? 



The simple answer is that no man knows. The wisest 

 physicist of to-day will assure you that he knows abso- 

 lutely nothing of the why of gravitation that he can 

 no more explain why a stone tossed into the air falls 

 back to earth than can the boy who tosses the stone. 

 But while this statement puts in a nutshell the scientific 

 status of explanations of gravitation, yet it is not in 

 human nature that speculative scientists should refrain 

 from the effort to explain it. Such efforts have been 

 made ; yet, on the whole, they are surprisingly few in 

 number ; indeed, there are but two that need claim our 

 attention here, and one of these has hardly more than 

 historical interest. One of these is the so-called ultra- 

 mundane-corpuscle hypothesis of Le Sage; the other is 

 based on the vortex theory of matter. 



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