10 



The Evolution of the Universe 



side of this, the next chister of galaxies is eight milhon hght years 

 away. 



The universe and its parts are in constant motion. The earth 

 rotates on its axis and, in addition, revolves around the sun. The 

 sun and other stars also rotate, and, in addition, they sometimes 

 have distinctive and highly individual paths, or orbits, within the 

 galaxy. Each galaxy rotates as a whole. The various parts of our 



Fig. 3. The Southern Milky Way photographed with a special 140° camera 

 at Yerkes Observatory. This sliows our galaxy edge on including the central 

 core of stars and the disk of dust and gas. (Photograph by A. D. Code and 

 T. E. Houck.) 



