260 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 31 



definite bodies. On one of these bodies at least, we know that an 

 organization of the atoms proceeded so far as to form not only land 

 and water, but even that highest type of organization which we call 

 life. And in the course of this mysterious process there finally 

 emerged the brains of human beings, who have just recently begun 

 to look back and to inquire into the makeup of the star from which 

 they came. 



It is an extremely interesting problem to try to explain with the 

 help of physics and mathematics why a certain amount of material 

 isolated in space should take on the particular size it does and begin 

 to throw out in all directions energy at a particular rate. For every- 

 thing we now know indicates that if you should put a certain number 

 of million tons of cold stuff off in space it would do just that. If 

 there were much more than this particular amount it would probably 

 break up, and if there were much less it would never shine at all. 



Another reason for making an intensive study of the stars is the 

 hope that such a study may supplement physics as we know it in 

 our terrestrial laboratories. The stars provide us with a wide variety 

 of conditions. The temperatures at the surfaces of many far exceed 

 any which we can as yet produce, while the pressures in their atmos- 

 pheres are often lower than any which we can obtain in the labora- 

 tory. It is true that some things about the way atoms can behave 

 have been learned first from the stars in recent years, but just now 

 it seems more likely to be the other way about, and that physics, 

 especially theoretical physics, will help to put together one of the 

 most interesting puzzles known to us. And yet inside the stars is 

 guarded the secret of at least one process which at present there is 

 no prospect of duplicating in any terrestrial laboratory — the conver- 

 sion of matter into energy. 



If we could be allowed to ask 10 questions about any star and have 

 them answered, I think they might be these : 



1. "Wliat is its distance from us ? 



2. What is its velocity in space? 



3. Wliat is its true luminosity or candlepower? 



4. How large is it, in miles? 



5. What is its mass? 



6^ What substance is it made of? 



7. What is the temperature at its surface and how does it change 

 toward the center? 



8. What is the pressure in its atmosphere and how does it change 

 toward the center? 



9. How long is the life of a star? 



10. The most interesting question of all, What is the source of its 

 continual flow of light and heat? 



