GRAVITATION VERSUS INERTIA 37 



swaying-, or dipping motion whereby it points out an 

 oval figure on the ceiling, so does the axis of our sys- 

 temal top point out just such another figure on the sky. 

 People generally are under the impression that the 

 earth's axis points directly to the pole star, and that it 

 always has done and will always continue to do so. 

 This however is not the case. If you can imagine the 

 axis of the earth to be a smoothly bored hole and your 

 eye looking through it from the south end, the sky 

 point you see will describe a circle of 23 1 / 1 > degrees 

 around the ecliptic's north pole in approximately 25800 

 years, provided, of course, the movement continues uni- 

 form. The effect of this movement is to make our 

 "tropical" (weather) year about twenty minutes 

 shorter than the sidereal one. In technical language, 

 this phenomenon is called the "precession of the equi- 

 noxes", because the instant in this year when night and 

 day become of equal length precedes by 20 minutes the 

 occurrence of the same event last year. Newton guessed 

 that this phenomenon was caused by the sun's attraction 

 on the equatorial bulge of the earth. If planets attract 

 each other by their centers of figure and not by their 

 centers of gravity, he was right. My own view is that 

 it is the effect of this top-swaying motion of the solar 

 system; and that the system, in addition to its falling 

 movement, has a backAvard soaring, or wheeling mo- 

 tion in a large circle (being the result of reaction) 

 requiring about 26,000 years to describe, and furnish- 

 ing what I venture to suggest is the larger parallax 

 for which astronomers have been long wishing. If this 

 view is indeed correct, it would signify that the earth's 

 extended axis is describing a double cone, whose com- 

 mon apex is a point in space perhaps a light year from 

 us, the apparent celestial circle described being the out- 

 line of the base of the inverted cone. 



