The Egypt Code (38 page)

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Authors: Robert Bauval

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In the Middle Kingdom, the so-called decanal lists were used. Decans were 36 stars (or groups of stars) whose heliacal rising (the day of the first rising before dawn after a period of conjunction with the sun, i.e. invisibility) occurred in subsequent “weeks” (the Egyptian week was made out of 10 days). In this way, the calendar was divided into decans (36 × 10) plus 5 epagomenal days associated to special decans as well (the calendar I am speaking about is the so-called religious or Sothic one, based on heliacal rising of Sirius which therefore was the first of the decans).
It was shown by Neugebauer and Parker that possible decans must lie in a band south of the ecliptic (decanal band) but they considered explicit identification of decans to be impossible. This is untrue and, in fact, today we do have a quite clear picture of which stars the decans represented (Belmonte 2001a,b). Decans were used to keep track of time during the night as well. This is proved by the so called Star Clocks in which hours during the night are counted associating the last hour of the first day with the decan which has heliacal rise in that day. After one “week” the rising of this decan shifted back in time to signal the previous hour, and another decan signals the last hour, and so on 12 times. Of course each hour had a non-fixed length. One can say that for us one hour has a fixed length and that the night has a variable length in the course of the year, but for the Egyptian it was the opposite (our 24 hour division of the day comes from the 12+12 Egyptian division added to the fixed length Babylonian division of hours).
In the New Kingdom the decans were observed at the meridian transit rather than at rising, but the way of keeping track of stellar events was similar. This is evident in the so called Ramesside star clocks. In a Ramesside star clock a man (an assistant of the astronomer, or perhaps a statue) is seen behind a list of 9 columns and 13 levels. Levels are associated with hours of the night, columns with parts of ‘the reference man’, and spots signal the transit or position of stars during the night. The framework was changed each 15 days. I will not enter into further details on the problems of interpretations of such texts. The point I want to stress here is, that such astronomical devices, although depicted in the tombs (as ‘guides to the soul during the night’) were almost certainly copied from scientific sources (the reader can, if he likes to, add quotation marks to the word ‘scientific’ but I will not do so). In fact, already in the Middle Kingdom Egyptian astronomers were able to keep accurate track of 36 stellar objects taking into account their motion (hour of rising, period of invisibility and so on) and therefore they should have selected such properties from a huge amount of observational data. It is absolutely certain that one can discover a precessional effect in the heliacal rising of a star with data accurate to ½ of degree in, say, three centuries. This led Pogo (1930) and Zaba (1953) to propose that precession was probably discovered very early in Egypt. It is, in addition, worth mentioning that several authors have proposed, in order to explain the curious arrangements of the constellations in the famous round picture of the sky known as the Dendera Zodiac, that it could contain a reference to the precessional movement of the north pole (see for example Trevisan). The Zodiac is however dated to the first half of the last century BC, and therefore after Hipparchus’ discovery. Again, we do not have any explicit records which can be associated unambiguously to the discovery of a precessional effect.
Fig. 2
Examples of Ramesside star clocks.
 
2.4 Mesoamerica
 
As is well known, the Maya kept track of astronomical data in a written and extremely accurate way (Aveni 2001). Unfortunately, only four Maya ‘codices’ survived the
auto da fe
during which the bishop of Yucatan, Diego de Landa, condemned all the heretic books. Such codices contain data about eclipses, Venus and Mercury. The Data is so precise (for instance, the Venus table in the Dresda codex is based on tens of years of observations) that the ability of the Maya astronomers in taking extremely accurate measures is beyond any doubt. However one cannot discover precession using the motion of the sun, of the planets and of the moon, and we do not possess any record of star observations by the Maya (the unique exception possibly being in the so called Paris codex, which is still not fully understood).
3.0 Astronomical Alignments
 
So far, we have discussed possible textual evidences. There is, however, another possibility to keep track of celestial motions and to leave astronomical data to successors as a heritage, namely the construction of stellar alignments. Following their accuracy during a few centuries one can easy discover precessional effects (I am using here an abuse of notation calling ‘stellar’ the alignments pointing to stars different from the sun).
3.1 Egypt: Orientation of Temples
 
The pioneer in the studies of the astronomical orientation of temples in Egypt was Norman Lockyer (1894). In his book he studied the orientation of many temples, but I shall discuss in details here only the case of the two main Theban temples, Karnak and Luxor, because it suffices for our purposes.
These two temples have a millenary history and were embellished and enlarged several times. In particular, different pharaohs in different epochs added further galleries in the direction of the main axis of both temples. If one looks at the plan of the Karnak temple, it is clearly seen that the temple was always enlarged maintaining strictly the original direction of the main axis. It was shown by Lockyer that this direction is that of the setting sun of the summer solstice. The work of Lockyer was criticised because hills at the horizon would have prevented the light of the setting sun from penetrating the gallery, and today we actually know that observations were performed at the other end of the temple in a chapel which - being on an axis parallel with the temple - is obviously oriented to the winter solstice sunrise (Krupp 1983, 1988). In any case, solstice alignment of the temple is certain, and of course, since precession does not effect the apparent motion of the sun, so any enlargement was added in the same direction.
Fig. 3
Plan of Karnak and Luxor temples.
 
The other main temple of Thebes, today called Luxor temple, is instead aligned to the stars. This is pretty clear because the axis was
slightly
deviated no less than four times, every time on the occasion of a subsequent enlargement which took place over the centuries. Unfortunately, although we do have several descriptions of the alignment ceremony of temples to the stars, called by the Egyptians
Stretching of the Cord
, we do not have a clear picture of how the ceremony actually took place. For instance, in many cases it is said that the alignment occurred towards the
Mes
constellation, i.e. the Big Dipper/Plough which the Egyptian saw as a Bull’s Foreleg, but we do not know exactly to which star it was made. It is as yet unclear therefore to which star or asterism the Luxor temple was aligned (Lockier proposal,
alfa-lyrae
or Canopus, is, as far as I know, still to be confirmed). In any case, the slight deviations in the temple axis clearly point to the discovery of a precessional effect.
3.2 Egypt: orientation of pyramids
 
It is very well known that the main pyramids of the fourth dynasty (the main three at Giza and the two Snefru pyramids at Dashur) were oriented to face the cardinal points with a high degree of precision. The deviation of the east side from true north is in fact the following:
Meidum -20′ ± 1.0′; Bent Pyramid -17.3′ ± 0.2′; Red Pyramid -8.7′ ± 0.2′; Giza 1 (Khufu) -3.4′ ± 0.2′; Giza 2 (Khafre) -6.0′ ± 0.2′; Giza 3 (Menkaure) +12.4′ ± 1.0′.
The precision achieved by the pyramid builders was so high that it is absolutely certain that the orientation method used was based on stars and not on the measurement of shadows (recently, the French mission directed by M. Valloggia has determined the orientation of the pyramid at Abu Roash [Mathieu 2001], probably constructed by Djedefre who ruled between Khufu and Khafre, to be - 48.7′, but this error is so out of stream with respect to the others that it points to a different, perhaps solar, orientation ceremony).
The stellar methods which have been proposed in the past, e.g. the observation of rising and setting of a bright star on an artificial horizon, are not affected by precession. However, as already noticed by Haack (1984), the data strongly point to the existence of a time-dependent font cause of systematic error and this font is certainly precession. This problem induced Kate Spence (2000) to propose a method of orientation - “the simultaneous transit” - which consists in observing the cord connecting two circumpolar stars, namely Kochab (b UMi) and Mizar (z UMa) when it is orthogonal to the horizon. Due to the precessional motion of the earth axis the cord does not always identify the true north: it has a slow movement which brought it from the left to the right of the pole in the 25th century BC. Plotting the deviation from north against time, Spence shows that the corresponding straight line fits well with the deviation of the pyramids i.e. to true north if the date of ‘orientation ceremony’ occurred for the Giza 1 pyramid in 2467 BC ±5y (although no written evidence of orientation ceremony exists for the old kingdom pyramids, the ‘Stretching of the Cord’ foundation ceremony is actually already present in the Old Kingdom stele called ‘The Palermo Stone’). If one, in turn, accepts the method as the one effectively used, the graph plotted can be used to calibrate the dates of construction of all the fourth dynasty pyramids, which turn out to be around 80 years later than usually accepted.
Further to Spence work, Belmonte (2001c) proposed that the method actually used consisted in measuring alignments between two stars (as Spence proposed) but using a couple of stars - probably Megrez (d UMa) and Phecda (g UMa) - which are not each other opposite to the pole. The pole is thus obtained by elongation of a cord lying below or over it. This looks more natural (at least for modern naked-eye sky-watchers) and reconciles the astronomical chronology with the usually accepted one. However, it should be noted that the astronomical dating of the so called air shafts of the Giza 1 pyramid (Trimble 1964, Badawy 1964, Bauval 1993) support Spence’s earlier chronology.
Fig. 4
 
The solution proposed by Spence for the orientation of the Giza 2 pyramid fits in the calibration line if and only if the corresponding point is ‘lifted up’ vertically in the positive region. To solve this problem, Spence speculates that the orientation of the second pyramid was carried out in the opposite season (summer instead of winter) with respect to the others (also in the Belmonte proposal the problem arises and has to be solved by assuming a special procedure for the orientation of the Giza 2 pyramid). I tend rather to think that a ceremony of religious nature, such as the orientation of a giant king’s tomb, could not occur scattered in time but rather in a fixed, precise time dictated by astronomical counting, such as those rituals connected with the Sirius cycle, and I have, therefore, proposed that the error in the orientation of the ‘second pyramid’ actually shows that it was constructed before Giza 1 or, more precisely, that the two projects were conceived together (it can be shown that this idea is not in contrast with any indubitable archaeological evidence: see Magli (2003) for details).

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