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

By Robert G. Bauval


It is well known that the monumental Pyramids of the Old Kingdom in Egypt, from the 4th Dynasty (c. 2500 BC) to the 6th Dynasty (c.2100 BC), have slopes 52° +- 2°, with two notable exceptions being the two pyramids at Dashur, with the Red Pyramid having a slope of about 43° 22' and the Bent Pyramid having half its height at slope of 54° 27' and the top half at 43° 22'. Today there are still some 25 royal pyramids standing in the 25 kilometres strip of desert land adjacent to the west bank of the Nile Valley near modern Cairo. Most have their core masonry sufficiently intact to allow relatively accurate measurements of their slopes. A recent batch of slope measurements were provided by Jaromir Malek and John Baines in 1984 and Mark Lehner in 1997, of which 17 pyramids spanning from the 4th to the 6th Dynasties can by analysed. The first, a pyramid attributed to the relatively unknown pharaoh Huni of the 3rd Dynasty, is generally thought to have been 'converted' into a true, smooth-sloped pyramid by the founder of the 4th Dynasty, king Snefru, the father of the Khufu builder of the Great Pyramid at Giza. I have thus considered the Meidum pyramid as being part of the 4th Dynasty trend.

PHARAOHDynastyLocationSlopes (Malek & Baines)Lehner
Huni3Meidum51° 50' 35"51° 50' 35"
Snefru4Dashur North43° 22' 00"43° 22' 00"
Snefru4Dashur South54° 27' 44"54° 27' 44"
Khufu4Giza51° 50' 35"51° 50' 40"
Djedefre4Abu Ruwash60° ~52° ~
Khafre4Giza53° 07' 48"53° 10' 00"
Menkaure4Giza51° 20' 25"51° 20' 25"
Userkaf5Saqqara53° 07' 48"53° 07' 48"
Sahure5Abusir50° 11' 40"50 11' 40"
Neferirkare5Abusir53° 07' 48"53° 07' 48"
Niussere5Abusir51° 50' 35"51° 50' 35"
Isezi5Saqqara South53° 07' 48"52° 00' 00"
Unas5Saqqara56° 18' 35"56° 18' 35"
Teti6Saqqara53° 07 48"53° 07' 48"
Pepi I6Saqqara53° 07 48"53° 07' 48"
Merenre6Saqqara53° 07 48"53° 07' 48"
Pepi II6Saqqara53° 07' 48"53° 07' 48"
Source: Atlas of Ancient Egypt by Jaromir Malek and John Baines (Adromeda Oxford 1984) and The Complete Pyramid by Mark Lehner (Thames and Hudson 1997).

No convincing explanation has, so far, been given as to why the Pyramid builders selected slopes of 52° +/- 2°. There are geometrical theories and also construction issues that have been proposed as an explanation in recent years, but none are very satisfactory. From table 1 we can see that the angle of slope most often encountered is 53° 07' 48", which occurs in nearly 50% of the Old Kingdom pyramids. This range of angles, from 54.5° to 51.7°, as can be seen from Table 1 above, bears a conspicuous correlation to the range of angles of the pole of the ecliptic of 54.5° to 51.5° at upper culmination as seen from across the pyramid fields of the Old Kingdom. In consideration of this, it is very tempting to inquire whether the ancient builders could have incorporated the angle of the pole of the ecliptic in their design of pyramids.

Let us examine this possibility.

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