i6 evolution: the ages and tomorrow 



in the cloud just before its final collapse. Dust clouds of all 

 sizes— some of the smaller ones being just at the point of final 

 condensation— have been found all over our galactic system. 

 In fact, it is now known that there is actually more matter 

 outside the stars than within. 



Apparently, the universe in its present form is still evolv- 

 ing new stars and new planets— new localities without num- 

 ber where evolution, undiscouraged by failures elsewhere, 

 may explore again and again every possible variation in an 

 eternal striving toward understanding. Although the con- 

 ditions necessary for the appearance of conscious under- 

 standing are extremely special, it is assumed that among the 

 great number of planets, star-scattered in a galaxy, a few do 

 offer sufficient opportunity for life. Modem astronomy is 

 lavish with size and number, even when speaking tentatively 

 in terms of the finite— of millions upon millions of galaxies, 

 each with billions of stars. 



It was a great year for science when, in 1924, Edwin 

 Hubble with his 100-inch reflector first resolved the galaxy, 

 Andromeda Nebula. A great deal has been learned about the 

 macrocosm since that year: the chemical composition of the 

 stars, mostly hydrogen; the source of stellar energy, a nu- 

 clear reaction building hydrogen into helium; the kinds and 

 sizes and distribution of the stars; the kinds and sizes of the 

 vast galaxies of space. A cosmologist can now take this 

 growing knowledge, along with all the related advances, 

 and begin to piece together a system of the universe. 



One of the most sensational of all cosmologies is the con- 

 cept that the universe is exploding, an idea that has risen out 

 of the discovery by V. M. Slipher and Edwin Hubble that 

 spectral lines of light from the galaxies show a shift to the 

 longer wavelengths (red shift), as though this were a Dop- 

 pler effect and the galaxies were receding at great speeds. 

 Einstein had originally assumed on the basis of his equations 

 that the universe is finite: a closed, four-dimensional, spher- 

 ical structure. His was a static cosmos. The Abbe Lemaitre 



