742 



SCIENCE 



[Vol. LVI, No. 1461 



most penetraiting (tlieoretical ability. For many 

 yeais measurements have been going on at Hair- 

 vard Observatory ajid elsewhere on the march of 

 brdghtneBS of such stars ia:s Algol, in ivhich we 

 see a pair of objects whieh in their rotation about 

 their common eeii,ter of gravity periodically 

 eclipse each dther. Dr. Russell showed how tlie 

 elemiontis of the eclipse, comprising the observed 

 brightness and the oorresponding times, could be 

 treaited in order (to give probable relative values 

 of the densities of stars in the different eclipsing 

 systems, and woith his pupil and collaborator, Dr. 

 Sha,pley, who applieij Russell's methods, the re- 

 sults foir 87 stars were obtained and published in 

 1913. 



In the meanwhile, many additional stars had 

 been measured for distance from the earth, and by 

 combining the information tlien available, Russell 

 showed in 1913 that the stars -may be divided into 

 two estJ-aoxdinary sequences which, following 

 Hertzsprung, he called the ' ' giaiQts and dwarfs. ' ' 



In short, the ' ' giants ' ' beginning with the red 

 and going on to the yellow, white and blue, form 

 a series of substantially equal output of light far 

 in excess of that which is expended by our sun, 

 and their densities, beginning with the red stars 

 which are so rare that the miaiterial of which they 

 are composed is more to be compared to a fairly 

 high vacnum than to ordinary gaseous, liquid or 

 solid densities, increase as the sequence goes on 

 until wdtih ithe blue stars tihe density has become 

 much more eonsiderable. 



From this point the deaoemding series of the 

 dwaifa begins, and .the density reaches in our 

 yellow sun about one and one half times that of 

 water and from this goes on to the very red and 

 small stars whose density is as great or greater 

 tban that of the earth itself. 



So regular is the light progress of tihis fascinat- 

 ing series of dwiarf staxs thait if one merely ob- 

 serves the type of speotrum which one of its mem- 

 bers possesses he can tell with reasonable limits 

 the total amount of light which is emitted and 

 therefore, in connectiom with its apparent bright- 

 ness, can determine the probable distance away 

 f liom .the earth in space. 



On the other hand, if a duster, such, for in- 

 stance, as the great cluster in Hercules which are 

 known to be stars of subatantially equal distance 

 from the earth, contoins a group of stars of ap- 

 proximately equal brightness ranging through all 

 the types of spectrum from ithe blue to the red, it 

 follows .that Ithey are all giants and therefore 

 emitting light of a roughly known quantity thou- 

 sands of times in excess of tliait emitted by the 

 sun, and from this the distance of itlie cluster 



can be fairly well estimja*ed. Such considerations 

 have been pursued by Dr. Shapley in regard to a 

 great many of the clusters of stars, and have led 

 Mm to assign distances in the stellar sj-stem some 

 tenfold in excess of those which have been gen- 

 erally assumed before. 



Professor Russell, itaikiag as .his text tiie 

 frescoes on the walls of the hanquet hajH which, 

 being known as the "College Boom," was dec- 

 orated exclusively with scenes of college sport, 

 replied as follows : 



Team work wins in science as well as in games. 

 But there is this important difference, that seien- 

 tifio team work is free cooperation; there is no 

 coaching and no central control. 



If I have done anything to deserve this medal, 

 it is because of the many men who have com- 

 tributed to these investigajtions. I was particu- 

 larly indebted to Professor Pickering of Harvard 

 for the encouragement tlhat he gave to a young 

 and unknown instructor in his science. When I 

 talked to him abont my proposed work on stellar 

 parallaxes, he volunteered his aid and provided 

 me with observations of the magnitudes and 

 -speotra of 300 stara, which gave me the first evi- 

 dence of the existence of giant and dwarf stars. 

 Robert Ball says thaJt "astronomy consists in 

 sitting up all night and doing arithmetic all day. ' ' 

 Some men like the one thing better than the 

 otlier. My part has been largely doing arithmcttic. 

 Buit this would noit have amounted to anything 

 without the men who were willing to sit up aill 

 night. Here, again, is scientific team work. 



At Princeton we are working on double stans. 

 If you can guess how massive a star is, you can 

 calculate how far away it is. If you can guess 

 at ithe mass of a double star you can calculate its 

 distance. Now double stairs — ait least, those with 

 spectra of .the same sort — are remajkably alike 

 in ma&s, so .that the guess .thalt those which we 

 have not yet investigated are similar to those 

 which we know about is likely to be a very good 

 guess. In this way we have nearly finished calcu- 

 Iflrting the distances of about 1,600 double stars. 

 To calibrate our formula, we use parallaxes de- 

 termined in other ways, which have been gen- 

 erously sent us (published and unpublished ma- 

 terial ailike) by Drs. Adams and Schlesinger. All 

 tlie investigators .of stellar distances are now 

 playing on .the same team. 



Not only must asrtironomers cooperate in re- 

 search, but they must have the aid of the phys- 

 icists and chemists. To know more about the 

 stars we must know more about a/toms. In fact, 

 we would not know anything about the stars, even 



