Table 40 73 



PROBABLE VALUES OF THE GENERAL PHYSICAL CONSTANTS 



(As of January 1, 1929) 



(Considerably abbreviated from paper by Raymond T. Birge published in Phys. Rev. 

 Suppl., vol. 1, no. 1, July, 1929, which see for further details) 



Some of the most important results of physical science are embodied in the 

 numerical magnitudes of various universal constants; the accurate determina- 

 tion of such constants has engaged the time and labor of many most eminent 

 scientists. Some of these constants can be evaluated by various methods. Each 

 has been investigated by various persons, at various times, and each investiga- 

 tion normally produces a result more or less different from that of any other 

 investigation. Under such conditions there arises a general and continuous need 

 for a searching examination of the most probable value of each important con- 

 stant. An investigation of the values of general constants in current use reveals 

 a surprising inconsistency, both in regard to the actually adopted values and to 

 their origin, probably because of the fact that it is almost impossible to find 

 a critical study of the best values, sufficiently up-to-date to be really reliable, 

 and sufficiently detailed to explain the inconsistencies found among older 

 tables. 



( 1 ) In what follows " each general constant has been determined from the 

 available data, beginning with that constant whose value depends least on other 

 constants. The value thus adopted has then been used consistently in the calcu- 

 lation of each succeeding constant for which it is an ' auxiliary constant '. No 

 attempt has been made to compare the results of different investigators until 

 these have been made properly comparable by the use of the same value of 

 each auxiliary constant. 



(2) " Each constant has been calculated from the available data by the use, 

 as far as possible, of formulas which involve no approximations. 



(3) "Each constant has been recalculated, whenever it seemed necessary, 

 by analytic methods — usually by the method of least squares." 



Attention should be directed to two important sources : 



( 1 ) The International Critical Tables ( 1926) publish a list of nine so-called 

 "Accepted Basic Constants," each with its " Uncertainty." A list is given of 

 21 constants derived from these, and also certain other conventional and ex- 

 perimental constants. The I.C.T. 1 list was adopted in 1923 ; since then im- 

 portant work on nearly every constant has appeared. It was prepared with the 

 aid of various scientific societies and individuals. The values are not claimed 

 to be the best values then available, although obviously an attempt was made to 

 obtain the best values. The chief weakness of this list is the lack of any state- 

 ment as to their origins. By correspondence and in other ways Doctor Birge 

 has obtained such information, and specific references to this are made in the 

 various sections to follow. 



1 I.C.T. will be used for International Critical Tables, 1926. 

 Smithsonian Tables 



