Building the Great Pyramid

Page 3 of 8

• 1. Great debate
• 2. Levelling
• 3. Aligning
• 4. Ramps
• 5. Raising blocks
• 6. Quarrying
• 7. Cutting blocks
• 8. Find out more
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Aligning

Egyptian architects, surveyors and builders are known to have used two specialised surveying tools, the merkhet (the 'instrument of knowing', similar to an astrolabe) and the bay (a sighting tool probably made from the central rib of a palm leaf). These allowed construction workers to lay out straight lines and right-angles, and also to orient the sides and corners of structures, in accordance with astronomical alignments.

It is clear that the Egyptians were using their knowledge of the stars to assist them in their architectural projects from the beginning of the pharaonic period (c.3100-332 BC), since the ceremony of pedj shes ('stretching the cord'), reliant on astronomical knowledge, is first attested on a granite block of the reign of the Second-Dynasty king Khasekhemwy (c.2650 BC).

This pedj shes ceremony relied on sightings of the Great Bear and Orion constellations, aligning the foundations of the pyramids and sun temples very precisely with the north, south, east and west. They usually achieved this with an error of less than half a degree. In later periods, the process of stretching the cord continued to be depicted in texts and in the reliefs of temples such as that of Horus, at Edfu, but it appears to have gradually become just a ritual, since these temples were aligned less precisely than the earlier ones, often simply with reference to the direction of the river.

How did this astronomically based surveying work in practice? The British Egyptologist IES Edwards argued that true north was probably found by measuring the place where a particular star rose and fell in the west and east, then bisecting the angle between these two points. More recently, however, Kate Spence, an Egyptologist at the University of Cambridge, has put forward a convincing theory that the architects of the Great Pyramid sighted on two stars (b-Ursae Minoris and z-Ursae Majoris), rotating around the position of the north pole, which would have been in perfect alignment in around 2467 BC, the precise date when Khufu's pyramid is thought to have been constructed. This hypothesis is bolstered by the fact that inaccuracies in the orientations of earlier and later pyramids can be closely correlated with the degree to which the alignment of the two aforementioned stars deviates from true north.

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Published: 2002-10-28