194 ANNUAL REPOKT SMITHSONIAN INSTITUTION, 1913. 



arranged to suit other conclusions. If we assume the line of specu- 

 lation stated above we must be interested in the following statement 

 of Prof. Kapteyn : 



There is another problem involved in our observations which might seem to 

 be of no less importance than the one just now considered. How have we to 

 explain the fact that the internal velocity of the stars increases with ageV The 

 astronomer who, in the study of the motion of the heavenly bodies, has found 

 hardly a trace of any other force than gravitation, will naturally turn to gravi- 

 tation for such an explanation ; and it really seems a necessity that under the 

 influence of their mutual gravitation, bodies which at the outset have little or 

 no relative motion must get such a motion, which, up to a certain limit at least, 

 will increase with time. Thus far there is no great difficulty. But now let us 

 look further back in time, back to the time in which the stars had not yet been 

 formed, in which matter was still in its primordial state. If it be true that 

 mutual attraction of the stars has generated such an enormous amount of inter- 

 nal motion in the time needed by the stars for their evolution from helium to sec- 

 ond or third type stars, how have we to explain the fact that we find that same 

 matter nearly at rest at the first stage of stellar life? That in the prehelium ages 

 gravitation had produced hardly any motion? He who believes in a creation 

 of matter at some finitely remote epoch may find no difliculty in the question, 

 but to him who does not, there is something astonishing to see matter behave 

 as if there were no gravitation. What may be the explanation? Is there really 

 no gravitatiun in primordial matter, or is there another force exactly counter- 

 balancing its effects? 



I have no solution to offer. I simply wish to i)oint out that here is a great 

 i)roblem, which in my opinion deserves the attention of the physicist no less 

 than that of the astronomer. 



