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Precise astronomical dating of the Great Pyramid: A Breakthrough or Old News?

By Robert Bauval, November 2000

Dozens of newspapers and websites announced yesterday (16 November 2000) a major 'breakthrough discovery' by Kate Spence, a PhD researcher at Cambridge University that was published in the journal Nature. The main 'breakthrough' hailed by the media concerns the accurate dating of the Great Pyramid by modelling the precession of the transit of two stars, Kochab (in Ursa Minor) and Mizar (in Ursa Major), at the north meridian of the sky. According to Kate Spence,

"The ancient Egyptian Pyramids of Giza have never been accurately dated... Modelling the precession of these stars yields a date to the start of construction of the Great Pyramid that is accurate to ±5yr, thereby providing an anchor for the Old Kingdom chronologies" (Nature, Vol. 408 p.320, 16th November 2000).

In addition Kate makes two further claims: (a) that the simultaneous transit of these two stars was used by all the Pyramid Builders of the Old Kingdom from the 4th Dynasty onwards to anchor their pyramids to true north, and (b) that because of this technique the alignments of their pyramids fell into 'error' due to the precessional shift of the stars (which only aligned in simultaneous transit with true north in 2467 BC).

I have absolutely no problems with regards the claims (a) and (b). With these Kate Spence has, indeed, introduced some interesting new ideas that merit careful examination and critical appraisal. However, I do very seriously object with to Kate’s claim that she is the first to accurately date the Great Pyramid using stellar alignments. Such a 'breakthrough' took place several years ago in 1993-5 and was achieved definitely NOT by Kate Spence but by me and indeed published on several occasions.

Let us look at the facts.

First of all, how and why did Kate Spence get involved in Pyramid dating and precession? Until November 1999 not many people knew of Kate Spence. She made her entry in the big media by being part of BBC Horizon's team of academics (Atlantis Reborn, 4 November 1999) selected to 'demolish' the work of Graham Hancock and myself. As viewers may remember, Kate was especially chosen to give a critical blow to the Orion-Giza correlation theory.

Actually Kate had done a bit of TV some time before, when she had been 'discovered' in 1995 by BBC's producer Chris Mann of the Ancient Voices programmes. Chris Mann was the producer of The Great Pyramid: Gateway to the Stars shown on BBC2 in February 1994. This documentary was based on my book, The Orion Mystery, and its success prompted Chris Mann to develop a new department at the BBC called Ancient Voices to investigate mysteries of the past. Kate Spence was given a 'screen test' and eventually participated in several programmes including one on Tell El Amarna and another on Noah's Ark.

I met Kate in Cambridge in November 2000 when she confessed to me that she was at first open-minded about The Orion Mystery and had in fact intended to include it in her PhD. thesis, but was eventually dissuaded by her colleagues. She is now a fierce opponent. Her 'breakthrough discovery' works like this: In a 'remarkable insight' (according to The Independent 16 November 2000, p. 14) Kate noticed that when the star Kochab (Beta Ursa Minor) reached its upper culmination at the meridian in c. 2467 BC, it did so by being directly vertically above the celestial north pole and also the star Mizar (in Ursa Major). She concluded that the Pyramid builders must have noticed this too, and assumed this 'invisible vertical line' to be true north and consequently aligned their pyramids towards it. Being unaware of the slow precessional drift, and thus not realising that the 'invisible vertical line' shifted a fraction away from true north, they all misaligned their pyramids by an equal deviation, except Khufu (Cheops), builder of the Great Pyramid, who, luckily, built his pyramid by chance nearer the date of 2467 BC. Here below is the stellar alignment for 2467 BC which Kate used (from New Scientist web article, November 16th):

Stellar alignment for 2467 BC which Kate used

In my book The Orion Mystery published in 1994, Plate 15a shows precisely the same stellar alignment used by Kate Spence, with ancient Egyptian stellar-deities superimposed. This alignment and others were used by me to date the Great Pyramid to c.2450 BC, plus or minus 25 years, thus within a range of 2430 BC to 2470 BC. It is generally agreed that a plus or minus tolerance of 20 arcseconds should be taken into account for naked-eye observations of stars, hence the need for a ±25 years deviation. Here is a reproduction of Plate 15a:

Reproduction of Plate 15a

In actual fact, the use of the upper culmination of the star Kochab when it is directly over the north celestial pole and also over the star Mizar in order to calculate the age of the Great Pyramid was employed in several articles published by myself in the Oxford journal Discussions in Egyptology (DE) in 1993-4. First in 1993, I published an article in DE (Vol. 26 pp.5-6), which used the Pole Star and precession to suggest, "the age of the great pyramid must be re-dated to 2475-2425BC, thus average c.2450BC."

Then in 1994 I published three further articles in DE (vol. 28 pp.5-13 & vol. 29 pp. 23-28; vol. 31, pp. 5-13) which clearly showed with diagrams how the north face of the Great Pyramid (defined by the north shaft of the Queen's Chamber) was probably aligned to the upper culmination of Kochab as it stood vertically over the celestial pole and the star Mizar, also giving the date 2450 BC ±25 years for its construction. It was not necessary to use the star Mizar in the calculations, as the dating provided by Kochab was more than sufficient. Here are the specific statements in my books and articles:

DE vol. 28, 1994, p.7: "Precessional calculations show that, with a slope of 39 degrees, in c. 2450 BC the northern shaft of the Queen's Chamber (of the Great Pyramid) pointed towards the 'head' of Ursa Minor, the star Kochab, as the constellation culminated at the meridian (see diagram 4)."

Kochab, as the constellation culminated at the meridian

The Orion Mystery (1994) p. 270-1: "In previous articles it was shown that the two southern shafts pointed to Orion's belt and Sirius...the two northern shafts were directed to the pole star, Alpha Draconis, and to the head of Ursa Minor (Kochab).... All these alignments work for the same precessed epoch of c. 2450 BC plus or minus 25 years."
DE vol. 31, 1995, p. 8: "As for the two northern shafts, these were directed to the pole star, Alpha Draconis, and the 'head' of Ursa Minor (Kochab)... All these alignments work out for the same precessional epoch of c. 2450 BC +- 25 years."

To be fair, the idea that the precession of the equinoxes could be used to accurately date the Great Pyramid is not new. It is original neither to myself nor to Kate Spence. This method has been in vogue at least since 1865 when the astronomer Piazzi Smyth attempted it using the Pole Star Alpha Draconis. Later in 1964 astronomer Virginia Trimble also used the Pole Star as well as the star Delta Orionis to date the Great Pyramid to c.2600 BC. What IS original to me (and NOT to Kate Spence) is the use of Kochab (and other stars such as Sirius and Zeta Orionis) to arrive at a more accurate date of 2450 BC ± 25 years. What Kate Spence has done is merely to attempt to refine this date to ± 5 years, building on the original idea of an upper culmination of Kochab over the celestial north pole as shown in my books and articles.

The other two aspects of Kate Spence's thesis, where she alleges all the Pyramid Builders supposedly used her 'invisible line' (formed though Kochab, the pole and Mizar) and that this technique explains variation in the error of alignment of different pyramids, are in fact original to her. And she is very welcome to take the full credit for those ideas. According to Kate, the builders of the Second and Third pyramids at Giza used the same 'invisible line' in the north, but because of the slight precessional change over the years, they got their pyramids misaligned without knowing. In short, they were fooled by precession. Well, it depends on how you want to see this. It’s the old story of whether the proverbial cup appears half full or half empty. The Pyramid builders may not have been fooled by precession at all, as Kate suggests, but rather used precession to 'date' their own pyramids. Rather than been poor astronomers, this reasoning would show that, quite to the contrary of Kate's opinion, that the Pyramid Builders were geniuses with an amazing grasp of astronomy as well as being very precise surveyors indeed. But frankly, my personal view on this is that the slight misalignment of the two other pyramids at Giza (Khafre and Menkaure) has nothing to do with precession but more to do with the realities of building and engineering construction and the tolerances that one would expect them to achieve in aligning huge structures to true north. A fraction of a degree here or there is not unexpected, and such 'errors' may or may not have to do with precession. If anything, it merely shows that the builders of the Great Pyramid were better and more accurate engineers than their successors. But we knew that anyway. In truth, the misalignments are far too small to attribute to deliberation rather than mere engineering tolerances. Like the ongoing American Elections, the result is 'too close to call.'

Kate Spence, in one sweeping statement to the Daily Mail (16 Nov. 2000), branded the ancient Egyptian Pyramid Builders as lousy astronomers. Or, more politely, in her own words: 'they did not have a precise grasp of astronomy.' Her conclusion is paradoxical. On the one hand she assumes them to be so accurate in their stellar observation and ability to align huge monuments to almost pinpoint accuracy to the stars in order for her theory to work, then on the other hand says that they did not have a 'precise grasp of astronomy'. You cannot have it both ways.

Finally Kate Spence knows, or should know, the ethics of scholarly publication. Her failure to make proper reference to the published works of Dr. Virginia Trimble* and myself (especially because in the latter case the same stellar alignment is used to arrive at practically the same dating of the Great Pyramid) is thus surprising and inexplicable in view of the circumstances. But then the whole approach of the BBC Horizon programme, Atlantis Reborn, in which Kate Spence participated, was most inexplicable as well. The Broadcasting Standards Commission branded this programme’s treatment of my work on the stellar alignments of the Giza Pyramid ‘unfair’. It now remains to be seen how Kate Spence's claims in Nature will fare.

Robert G. Bauval

*Virginia Trimble, 1964, Astronomical Investigations Concerning the so-called Airshafts of Cheops Pyramid, In: Mitteilungen der Instituts fur Orientforschung (Akademie der Wissenschaften zu Berlin) Band 10, pp. 183-7. (A copy or this article can be found in the appendix section of my book The Orion Mystery (1994).

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