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Speaking of Velikovsky's idea that some extraterrestrial force, such as a comet fly-by, could cause the appearance of the Sun standing still, Sherrerd talks about the hypothetic causes and results, "severe peturbations...in the rotation of the Earth about its polar axis. One would think intuit-ively, at first glance, that such occurrences would require impossibly large angular decelerating and accelerating forces, which in turn would so totally disrupt the earth's crust as to make impossible any human survival.
"Sudden and major displacements in the geographical position of the Earth's polar axis would most likely require such unthinkable circumstances. Those geological shifts which have occurred during historical time involved at most a few degrees of arc distance on the surface of the globe, and were indeed tectonically quite disruptive at that.
"However, unusual changes in the Sun's apparent position in the sky would also result from major shifts in the celestial position of the poles, i.e., the direction of the Earth's spin axis in the celestial sphere. These could occur without large angular decelerating and accelerating forces and without major tectonic disruptions, by the phenomenon of gyroscopic precession. Since gyroscopic precession involves a temporary transfer of angular momentum from spin to precession, when beginning and terminating it moderately affects the rate of rotation of a spinning object and introduces small horizontal forces on points on its surface; but it significantly shifts the absolute orientation of the spin axis in space as long as the precession continues in effect."
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