ON THE NATUEE OF LIFE 209 



occur is highly improbable — so improbable that we have no 

 experience of them, though we can imagine them occurring. 



This means that, in addition to the physics that we know, 

 another and a transcendental physics is conceivable. 



The Improbability of Life in the Universe. — ^It follows from 

 what has been said that it is extremely improbable that any- 

 where in the entire universe energy is available for the production 

 of physical phenomena. It is easy to show that such is the 

 condition that we know, and that even in our individual, galactic 

 universe, where an initial store of energy is exhausting itself, 

 this availability is improbable. 



If we were able to travel away from the sun in every direction 

 and with the speed of light, we should reach the boundaries of 

 our solar system in about four hours. Then we should travel 

 outwards into cosmic space for over three years and a quarter 

 before coming to the nearest fixed star. This sphere of space, 

 containing only our solar system (so far as we know), is not, 

 however, empty, but is " full " of ether. The latter is the 

 " substance " of all energetic changes, but we must regard it as 

 inert, or physically inactive. Nothing happens in it of itself. 

 It can be temporarily strained or modified in some way, as when 

 potential energy is locked up in it, or withdrawn from it, or 

 when radiant gravity or gravitational energy is transmitted 

 across it. It is permanently modified in localised regions as 

 physical gravitating matter, which may or may not be the locus 

 of energy transformations. "We must think about it as some- 

 thing real, but physically dead or inert. What fraction of this 

 universal substance is, then, physically active ? 



Calculating the volume of this sphere of three and a half light 

 years in radius, we find that it is about 240 X 10^^ cubic miles. In 

 it practically the only cosmic body that contains available energy 

 is our sun, and this has a diameter of (say) 870,000 miles. Find- 

 ing its volume, we get the value 15x10^^ cubic miles. It is 

 now easy to find that our sun occupies about 1/2 X lO^^th of the 

 part of the stellar universe that we have in imagination ex- 

 plored. The probability, then, that we should find physical 

 activity anywhere in the region of space within three and a half 

 light years from our sun is something like 1 in 2,000 trillions. 



Now consider the probability that living matter exists in this 

 physically active fraction of the cosmic space which immediately 

 surrounds^us. We can hardly think of it as existent in our sun, 



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