Foundations of the Universe 287 



If all the molecules of a substance were brought to a stand- 

 still, that substance would be at the absolute zero of temperature. 

 There could be nothing colder. The temperature at which all 

 molecular motions would cease is known: it is -273 C. No 

 body could possibly attain a lower temperature than this: a lower 

 temperature could not exist. Unless there exists in nature some 

 process, of which we know nothing at present, whereby energy 

 is renewed, our solar system must one day sink to this absolute 

 zero of temperature. The sun, the earth, and every other body 

 in the universe is steadily radiating heat, and this radiation can- 

 not go on for ever, because heat continually tends to diffuse and 

 to equalise temperatures. 



But we can see, theoretically, that there is a way of evading 

 this law. If the chaotic molecular motions which constitute heat 

 could be regulated, then the heat energy of a body could be 

 utilised directly. Some authorities think that some of the 

 processes which go on in the living body do not involve any 

 waste energy, that the chemical energy of food is transformed 

 directly into work without any of it being dissipated as useless 

 heat energy. It may be, therefore, that man will finally discover 

 some way of escape from the natural law that, while energy can- 

 not be destroyed, it has a tendency to become unavailable. 



The primary reservoir of energy is the atom ; it is the energy 

 of the atom, the atom of elements in the sun, the stars, the earth, 

 from which nature draws for all her supply of energy. Shall 

 we ever discover how we can replenish the dwindling resources 

 of energy, or find out how we can call into being the at present 

 unavailable energy which is stored up in uniform temperature? 



It looks as if our successors would witness an interesting 

 race, between the progress of science on the one hand and 

 the depletion of natural resources upon the other. The 

 natural rate of flow of energy from its primary atomic 

 reservoirs to the sea of waste heat energy of uniform 

 temperature, allows life to proceed at a complete pace sternly 



