226 ETHER AND GRAVITATIONAL MATTER. 



ing- the very grcut velocity of 183(1 Groombridge, which he conckides 

 us follows: 



''If, then, the star in question belongs to our stellar system, the 

 masses or extent of that system nuist l)e many times greater than 

 telescopic observation and astronomical research indicate. We may 

 place the dilennna in a concise form, as follows: 



"Either the bodies which compose our universe are vastly more 

 massive and numerous than telescopic examination seems to indicate, 

 or 1830 Groombridge is a runaway star, flying on a boundless course 

 through intinite space with such momentum that the attraction of all 

 the l)odies of the universe can never stop it. 



"Which of these is the more probable alternative Ave can not pre- 

 tend to sa}^ That the star can neither be stopped, nor bent far from its 

 course until it has passed the extreme limit to which the telescope has 

 ever penetrated, we may consider reasonably certain. To do this will 

 require two or three millions of years. Whether it will then be acted 

 on by attractive forces of which science has no knowledge, and thus 

 carried back to where it started, or whether it will continue straight- 

 forward forever, it is impossible to say. 



"Much the same dilemma may be applied to the past history of this 

 ))ody. If the velocitv of 200 miles or more per second with which it 

 is moving exceeds any that could be produced ])v the attraction of all 

 the other bodies in the universe, then it must have been flying forward 

 through space from the beginning, and having come from an intinite 

 distance, must be now passing through our system for the first and 

 only time." 



Sec. it. In all these views the chance of passing another star at 

 some small distance such as one or two or three times the sun's radius 

 has been overlooked; and that this chance is not excessively rare seems 

 proved by the multitude of Novas (collisions and their sequels) known 

 in astronomical history. Suppose, for example, 1830 Groombridge, 

 moving at 370 kms. per second, to chase a star of twenty times the 

 sun's mass, moving noarlv in the same direction with a velocity of 50 

 kms. per second, and to overtake it and pass it as nearl}^ as ma}^ be 

 without collision. Its own direction would )>e nearly reversed and its 

 velocity would be diminished by nearly 100 kms. per second. B}' two 

 or three such casualties the greater part of its kinetic energy might 

 be given to much larger bodies previously moving with velocities of 

 less than 100 kms. per second. By supposing reversed, the motions 

 of this ideal histor}^, we see that 1830 Groombridge may have had a 

 velocity of less than 100 kms. per second at some remote past time, 

 and may have had its present great velocity produced b}^ several cases 

 of near approach to other bodies of much larger mass than its own, 

 previousl}^ moving in directions nearl}^ opposite to its own, and with 

 velocities of less than 100 kms. per second. Still it seems to me quite 

 possible that Newcomb's brilliant suggestion ma}^ be true, and that 

 1830 Groombridge is a roving star which has entered our galaxy, and 



