GALAXIES ' 



By Harlow Shapley 

 Harvard University 



[With 2 plates] 



Like the galaxies themselves, the field of inquiry concerning 

 galaxies is large and not easily surveyed in a brief article. It will 

 be well to restrict the assignment and write only concerning a few 

 selected topics. 



Let us first try a bird's-eye view of our own galaxy. The bird 

 whose eye we would use needs to be a remarkable creature to reach 

 the remoteness necessary for an outside look. We cannot use 

 Cygnus the Swan, that heads in full flight along the northern Milky 

 Way, nor Aquila the Eagle, nor the big-billed Toucan, the Flamingo, 

 the Phoenix, the Goose, the Bird of Paradise, nor Corvus the Crow. 

 All these constellation birds are composed of stars that are bright 

 neighbors of the sun and distinctly localized far inside our own 

 galaxy. 



What we need is an observation point something like a million 

 light-years distant, well outside the bounds of the enormous Milky 

 Way system. It would be pretty satisfactory to settle our bird com- 

 fortably in the outer haze of stars of the Andromeda nebula. If the 

 observer be a contemporary of ours, he will be looking at our system 

 in terms of 8,000 centuries ago. It has been that long since the radia- 

 tion left the sun and its neighboring stars on its way to the retina 

 of the all-comprehending but quite imaginary bird now surveying 

 us from the Andromeda galaxy. 



Such a temporal disparity, 8 X 10 ^ years, is of no particular 

 moment in our considerations of the galaxies ; and short-term enter- 

 prises like the current western civilization, or even the whole history 

 of mankind, can be neglected in the cosmic panorama as too momen- 

 tary, too fleeting, for a clear recording. 



It is well known that the Milky Way star system is a much 

 flattened organization and that the sun and planets are well inside. 



'Reprinted l)y permission from the Sigma Xi Quarterly, vol. 30, No. 1. Jaimary 1942. 

 Included in Science in Progress, Series III, fall, 1942. 



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