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Did the Pyramid Builders of the Old Kingdom use the Pole of the Ecliptic?

By Robert G. Bauval


The Earth tilts some 23° 26' from the plane of the ecliptic. This angle, however, changes fractionally in cycles of 40,000 years from a minimum of about 22° 6' to a maximum of about 24° 30' due to a phenomenon known as the obliquity of the ecliptic. Calculations show that the angle of tilt has been steadily decreasing since the beginning of recorded history, c.3500 BC, at the average rate of about 40" per century. Using the accepted rigid formula [9], it can be shown that in c. 2500 BC, when the construction of the Giza pyramids began, the tilt of the earth's axis was 23° 58'. The Giza pyramid site is at latitude of 29° 59', which means that the north celestial pole of the sky was at an altitude of 29° 59'.

We always think in terms of the north celestial pole as being the focal point of the sky, an immovable imaginary point around which all the fixed stars seems to revolve in concentric circles. So entrenched is this idea that we ignore or are unaware that this imaginary point is not the true focal point of the sky at all. And even though the idea that the north celestial pole is a fixed point holds true for a short a very period of time, the statement becomes invalid over long periods of time because of precession. The fact is that the north celestial pole drifts away from the fixed field of stars at the rate of about 20" arcseconds a year due to the perpetual wobble-like cycle of our planet. Furthermore the north celestial pole will keep on drifting from the fixed star field up to a full 47° (about one quarter of the visible sky field) over its 26,000 years cycle. This is hardly a fixed point in terms of cosmic time. There is, however, another point in the sky which drifts away from the fixed star field at the very much slower rate of 0.4 arcseconds per year, that is 50 times slower than the drift of the north celestial pole and thus, by true definition, making it the real focal point of the sky. This point is known as pole of the ecliptic. Furthermore the pole of the ecliptic will only displace itself a mere 2.5° over its 40,000 years cycle.

The pole of the ecliptic is located in the heart of the constellation of Draco, approximately between the stars Zeta Draco and Al Tais. Assuming that the ancient astronomer-priests of Egypt began observing and recording the position of stars some 200 years before the dynastic period, say c. 3500 BC, up to the start of the 4th Dynasty in c.2500 BC, a simple calculations show that the position of the pole of the ecliptic would have displaced itself by only 6 minutes of arc (0.1°), over this whole 1000 year period. On the other hand the north celestial pole would have been displaced by 333 minutes of arc (5.55°). Imagine a dartboard where one dart (the pole of the ecliptic) is 1 cm away from the bull's eye and another (north celestial pole) is 50 cm away, and you will get the picture. The pole of the ecliptic will cross the meridian twice each day i.e. upper and lower culmination. Calculations show that during the Pyramid Age, and as seen from the latitude of Giza (29° 59'), the pole of the ecliptic would have had its upper culmination at the meridian at an altitude of 53° 57' (29° 59' + 23° 58') . The table below shows the altitude of the pole of the ecliptic at upper culmination at the meridian at different latitudes/locations in Lower and Middle Egypt, roughly encompassing the region of pyramid building during the Old Kingdom:

LocationLatitudeUpper culmination of Pole of the Ecliptic
Abu Ruwash30° 02'54° 00'
Giza29° 59'53° 57'
Dashur29° 45'53° 43'
Hawara29°15'53° 13'
Wadi Sannur29° 00'52° 58'
Beni Hassan28° 00'51° 58'
El Amarna27° 30'51° 28'
Altitude at upper culmination of the pole of the ecliptic From difference location in Egypt.

The angle of upper culmination of the pole of the ecliptic thus varied +/-2° from 52° depending where you stood in the desert region from Abu Ruwash to El Amarna.

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