432 THE POPULAR SCIENCE MONTHLY 



MEASUEING HEAT FROM STAES 



By Dk. W. W. COBLENTZ 



I. Some Questions Xnsweeed 



IF the title of this paper had been chosen as, " Measuring Heat from 

 Stars — Of What Practical Use Is It Anyway?" it would express 

 the feeling of the average interviewer. The question is not meant to 

 be contemptuous. It is the expression of the mind that figures every- 

 thing on the basis of an immediate return upon his investment. 



The interrogator may be one "engaged in writing an article for 

 some magazine " and he must needs " tell the lajnnan the practical side 

 of the subject." Suppose I, in turn, ask my interrogator the question : 

 " Of what prospective use was your layman when he was in the first 

 stages of development?" Said interrogator shrugs his shoulders, 

 smiles, and admits that perhaps the " layman" is not the only one to 

 be considered; that some of the results of investigations must go into 

 the great storehouse of knowledge, no one knowing what their ultimate 

 use may be ; that the great unknown can be explored only step by step ; 

 that each achievement may be only one more link in the chain of knowl- 

 edge, perhaps to be disputed and refuted by some future investigator 

 or perhaps be put to some practical use of some future " layman." 



Another question raised is, "Why the Government should be meas- 

 uring the heat of stars?" not realizing that such activities are inci- 

 dental, conducted to assist, if possible, its citizens in every possible way. 

 The narrow-gauge college professor may perhaps take it as an intru- 

 sion upon his field. To such an one the writer can but tell the 

 lesson taught him some months ago, when one bright morning, on 

 walking through the woods, a loud commotion was heard in the top- 

 most branches of a tall oak tree. Two wood-peewees were quarreling 

 for the possession of this tree — as a place to catch flies ! There were 

 hundreds of other trees close by, then why quarrel about this one. How 

 like the scientific man, I thought. We quarrel for fields of research, 

 just as though the heavens were not ablaze with objects for investigation. 



A further question asked by the interrogator is, " Well, how do you 

 measure the temperature of the stars?" This question may be easily 

 dismissed by saying that we can not measure the temperature of the 

 stars. The best we can do is to attempt to measure the rate at which 

 they are losing heat. But until the past summer even this attempt was 

 of little interest to the astronomer. Heretofore experimenters were 

 glad to be able to record heat from a few of the brightest stars ; let alone 

 attempting to measure stars of the 6.7th magnitude which are about 



