AND ITS INHABITANTS 17 



nomena indicate the enormous elastic and explosive energy 

 resident in the sun's interior, an expansive potency held in 

 restraint by the equally prodigious power of the sun's gravity. 



Supposing then that the ancestral sun was subjected to tidal 

 disruption by the approach of another and possibly much more 

 massive star, it remains to be seen how the nebula resulting 

 from tidal disruption can become the embryo of an orderly 

 planetary system. If the matter were shot out from great 

 depths in the sun by its normal expansive forces plus the tidal 

 forces, the velocity of departure might rise high above the 

 observed velocities of 300 miles per second. If 400 miles or 

 more, it would be above the "critical velocity" of the sun. The 

 gravitative attraction of the latter could then never reclaim 

 that matter, because the decrease in the outward velocity due 

 to the solar attraction would never bring the velocity down to 

 zero, and could therefore never reverse the motion of the 

 escaping matter and bring it back to the sun. 



It is doubtful if the sun could have drawn back to itself 

 material expelled with a velocity of even 300 miles per second, 

 for the passing star, by lowering the gravitative power of the 

 sun on the line passing through the two, would temporarily 

 decrease on that line the critical velocity. In other words, it 

 would help to drag matter away from the sun, even though 

 that matter could not catch up to the passing star, but would 

 be left wandering in interstellar space, forming possibly come- 

 tary and meteoric material for other systems. But some, 

 or possibly all, of the matter of the exploded sun may have 

 had lesser velocities of escape and would consequently remain 

 within its gravitative control. In so far as it was not deflected 

 sideways by some extraneous force, it would fall back on the 

 surface of the sun as the water of a geyser falls back into its 

 pool. But the gravitative pull of the passing star would serve 

 as such an extraneous force, analogous to the wind which 

 blows part of the geyser water, a& it rises and falls, to one 



