MIRACLES OF SCIENCE 



within a distance of about two and a half radii, the 

 power of gravitation will suffice to tear the structure 

 of both bodies asunder. 



To make the illustration specific, if a body as large 

 as the earth were to come within something less than 

 10,000 miles of the earth, both our globe and the other 

 body would explode like bombs and their fragments 

 would be scattered out into space. This critical dis- 

 tance of two and a half radii (more exactly 2.44) is 

 known to astronomers as Roche's limit. Saturn's 

 rings lie within this limit, and seemingly illustrate 

 the law, as they consist of comminuted particles of 

 world-stuff. 



But suppose now that two stars hurtling through 

 space approach each other at such an angle as not to 

 come within the dangerous explosion zone (Roche's 

 limit) but on the other hand near enough to exert a 

 mutual tidal strain of tremendous power. Gigantic 

 tides will then be raised on each of the bodies, and 

 even though their structures as a whole are not dis- 

 rupted, there will be a vast eruption of their gaseous 

 substance from opposite sides of both bodies. 



That the tidal effect should be manifested equally 

 in opposite directions, is well understood by mathe- 

 maticians. To the non-mathematical mind, the fact 

 though puzzling is made familiar by the twice-daily 

 recurrence of the ocean tides. 



If we look closely at the photograph of a spiral 

 nebula, we shall see that the two spiral arms do in 

 point of fact originate exactly opposite each other in 

 the structure of the globular central nucleus. 



The eruptive mass which thus bursts forth with 



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