The hypothesis of a polar orientation (1/2)

Before using this original software, let's study the validity of one of the oldest hypothesis - that of a polar orientation, first voiced by John Herschel, then repeated by Charles Piazzi Smyth at the very end of the XIXth century (6). By the year 2800 BC, a relatively bright star, today known as Thuban or alpha Draconis, materialized the celestial North pole, that is to say, this imaginary point around which our planet, the Earth, rotates. This fictive point is located some thirty degrees above the northern horizon of the memphite stargazer. The whole celestial vault seems to rotate around it.

According to a memphite stargazer, everyone of the objects
shining in the sky seemed to rotate around Thuban.

The location of the star alpha Draconis on the celestial vault was then so notable that the terrestrial projection of the line joining this object to any point of the northern terrestrial hemisphere could well have led to the accurate determination of true North. But because of the precession of the world axis, Thuban slowly moved away from this specific position. As a result, its daily motion resembled more and more each year to the one of the others stars filling the sky, that is to say, to a rotation around the celestial North pole, its radius of gyration continually increasing with time. Henceforth, only the terrestrial projection of its lower and upper transit positions could led to the more or less accurate determination of true North (7).