216 



T. C. CHAMBERLIN THE GREATER EARTH 



the sun is represented by the line E. G., within the orbit of the moon, 

 0. M. At first thought, this position seems quite anomalous, if not ab- 

 surd. The moon is controlled by the earth, and yet its orbit is repre- 

 sented as lying outside the line marking equal gravity between the sun 

 and earth. The seeming anomaly depends on the relative motion of the 

 bodies concerned. If they were all standing still or were all moving at 

 equal speeds in the same direction, a particle on the line E. G. would be 



s. s c. 



DIAGRAM n 



Scale about (11,600,000,000.000 



Figure 2. — Diagram Ulustratinn Sphere of Control of Earth on larger Scale 



E., earth ; R. L., Roche limit ; E. G.. limit of equal gravity between earth and sun ; 

 O. M., orbit of moon ; E. S. C, earth's sphere of control ; S. S. C, inner earthward border 

 of sun's sphere of control, which extends outwardly several hundred astronomical units. 

 Shortest radius of earth's sphere of control, 620,000 miles (1,000,000 kilometers) ; long- 

 est, 930,000 miles (1,500,000 kilometers). 



attracted equally by the earth and by the sun; all bodies outside E. G. 

 would be drawn most toward the sun. But, as a matter of fact, the earth 

 and the moon are both moving around the sun in very similar orbits, and 

 hence the centrifugal component of their motions neutralizes a consider- 

 able part of the attraction of the sun, without appreciably affecting their 

 own mutual attractions. Their mutual attractions are therefore rela- 

 ively more effective than the sun's attraction for them. This is a case of 

 relativity, in the old familiar sense of the term. This seeming anomaly 



