THE REACTION OF THE PLANETS UPON THE SUN.^ 



By P. PuiSEUX.^ 

 Member of the Institute, Astronomer at the Paris Observatory. 



The popular preconception that the earth, with the sun rotating 

 about it, was the center of the universe, was overcome only through 

 the persistent efforts of astronomers and physicists. We will not 

 here review these memorable discussions, but will note merely the 

 result. Everyone capable of connected and geometrical reasoning 

 will become convinced that the position of the earth, face to face 

 with the sun, is that of a humble satellite, and that our globe, forced 

 to escort our daytime star in its mysterious course through space, 

 receives from this star its law of annual movement and at the same 

 time its indispensable ration of heat and light. 



Going from one extreme to another, the sun was believed to be 

 independent of the relatively minute planets which it carries along 

 with itself. It seemed that a fictitious observer, placed at its center 

 or on its surface, would have no occasion to suspect the existence of 

 other celestial bodies. Further j^rotected against any perceptible 

 action from the stars by their inmiense distance, the sun must lavish 

 its splendor, with no pay in return, and follow unperturbed its 

 undeviated path through space. 



THE INFLUENCE OF THE PLANETS ON THE MOTION OF THE SUN. 



This conclusion was in some respects too radical. An account of 

 this matter could be rendered onlj'^ when the penetrating genius of 

 Newton showed that the curved trajectory of a projectile, the revo- 

 lution of the moon about the earth, and the revolution of the earth 

 around the sun were three manifestations of the same law. This 

 law holds everywhere. Further, it is not a special privilege of the 

 center of any system. The bond exists, real though slight, between 

 any two particles whatever. The sun, as well as the humblest 

 planet, because of this bond, must undergo periodic variations in its 

 speed as well as in its shape. 



1 Lecture delivered at the Conservatoire des Arts et Metiers, Feb. 23, 1913. 



2 Translated by permission from Revue Scientifique, Paris, May 3, 1913. 



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