SUPRA-STARS AND LIVING GALAXIES 123 



ferent structures. These again must form a larger 

 aggregate, something we might call a " supra-star." 

 The diameters of the heavenly bodies known to 

 us average about 10 10 cm. Hence, by the "world- 

 ratio," we must expect the diameter of the supra- 

 star to be somewhere about 10 32 cm., or a hundred 

 billion light-years. 



The mass of our galactic system is nearly 10 42 

 grammes. By our argument from the law of 

 gravitation, the mass within the supra-star must 

 be as much greater as its diameter is greater. 

 This makes the mass of the supra-star 10 58 grammes 

 and its density 10~ 44 . The velocity acquired by a 

 body in falling from infinity to the surface of the 

 supra-star would be some 60 miles per second, and 

 might rise to 120 miles in penetrating to its interior. 

 This is not excessive in comparison with observed 

 " proper motions." 



The mass of the supra-star being 10 53 grammes, it 

 contains 10 11 times the mass of our galaxy. We 

 might say it contains 100,000 million galaxies. The 

 density of the galaxy being 10 22 times that of the 

 supra-star, each galaxy will have 10 22 times its 

 own volume to move about in without collision. 

 The average distance of the nearest galaxy will be 

 about ten million times the diameter of our galaxy, 

 or, say 10,000 million light-years, so that, if the 

 nearest galaxy happened to have consisted of 

 luminous stars for several thousand million years, 



