Technology and Engineering: Building the Pyramids

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Technology and Engineering: Building the Pyramids

Giza. The best-known monuments from ancient Egypt are the pyramids of Giza (circa 2585-2510 b.c.e.). They also serve as a good example of the way the Egyptians approached engineering and architecture. The Egyptians used extremely simple technology to accomplish sophisticated ends. Archaeological remains, relief sculpture, paintings, and experimental archaeology have all contributed to modern knowledge of Egyptian techniques for building the pyramids.

Supply and Transport of Materials. The Egyptians transported the stone used to build the pyramids by boat and sledge. Stone, quarried a long distance from the building site, was loaded onto boats. A relief sculpture carved on the causeway of the pyramid temple of Unas (circa 2371-2350 b.c.e.) depicted a boat carrying granite columns from Aswan to Memphis. The Autobiography of Weni, a text dating to Dynasty 6 (circa 2350-2170 b.c.e.), also described the hauling of large pieces of granite and alabaster by boat. Canals, dug directly to the site of the pyramids, allowed the Egyptians to bring the stone close to the building site by boat. The stone blocks rested on sledges, which resembled modern sleds, and their runners were designed to run on wet mud that was scattered on tracks built from a series of wooden frames filled with limestone chips and covered with plaster. Such roads have been discovered at Lisht near the Dynasty 12 pyramids of Amenemhet I (circa 1938-1909 b.c.e.) and Senwosret I (circa 1919-1875 b.c.e.). Large ropes were secured around the blocks, allowing men to haul them directly to the pyramid site. A painting from the Dynasty 12 tomb of Djeheutyhotep (circa 1842-1818 b.c.e.) the nomarch in the town of Bersheh shows 172 men hauling an approximately 58-ton statue in this manner. A man sprinkled water in front of the sledge, keeping the mud moist, as it proceeded along the track. Experimental archaeology has demonstrated that fewer men were needed to haul blocks of the size found at the Great Pyramid using these methods.

Obtaining Stone. Quarries were located near the building site of the Great Pyramids of Giza. The location of the

quarry may well have helped determine the site for the pyramids. Only the external stone covering of the pyramid traveled a long distance. The remains of the quarries at Giza supply some clues to how quarrymen worked. A man with a pick cut channels, wide and thick enough to allow wooden levers to enter, around the rectangular blocks that would be removed from the bedrock. The blocks were then pried from bedrock with levers. Though earlier reconstructions of this process suggest that wedges were used to remove the block, experimental archaeology indicates that wooden levers worked better than wedges. Modern quarrymen use iron wedges in this process. Further experiments with ancient tools made of wood, stone, and copper have demonstrated that 12 workmen can produce 8.5 stones in a day. The archaeologist Mark Lehner has calculated that a crew of 1,212 men working for twenty-three years—the Greek historian Herodotus’s estimate of the time it took to build Khufu’s pyramid—could have easily quarried all the stone in the Great Pyramid. These men, of course, worked in rotation.

Tools, Techniques, Operations . The Egyptians designed and used simple tools needed to build the pyramids. They used plumb bobs and square levels to ensure that corners of blocks were square and that surfaces were flat. These instruments were made of wood, twine, and lightweight stones. Stonecutters used copper drills and saws, probably using a quartz slurry to aid in the process. The slurry was a solution of water, sand, and gypsum. Remains of such slurries have been found in ancient cuts where they stain the stone green, the result of oxidation. Copper chisels were used to smooth the sides of stones. Copper is so soft that the chisels needed constant sharpening. Lehner estimated that each one hundred masons using such a chisel would require one full-time chisel sharpener. Large dolerite stones were used as pounders to excavate the channels needed to free a block from the bedrock. Finally, a mushroom-shaped stone with three grooves cut across the round section probably acted as a primitive pulley that could redirect the force on the ropes used to move blocks. All of the tools needed to perform the operations for building the pyramids have been found archaeologically.

Survey and Alignment . Three characteristics of the pyramids lead to questions about the Egyptians’ ability to survey and align buildings. First, the sides of pyramids are aligned to the cardinal points of the compass. Second, the corners of the pyramids form perfect right angles. Finally, the foundation of the pyramid had to be perfectly level in order to support the enormous weight of the upper courses.

Using the Stars . Alignment to the cardinal points of the compass was most likely accomplished by astronomical observation. Because stars appear to move in Egypt from east to west, true north could have been established by dividing the angle of a rising and setting star by two. Or the sun could have been used to establish true north though measuring the length of a shadow of a vertical at various times of the day. Neither method can be proved, but both could have been performed given Egyptian knowledge of astronomy.

Figuring Angles . Three methods have been proposed for establishing the right angles at the corners of the pyramids. A setsquare could have been used to establish the corner. The difficulty would have been to extend the lines of the square 754 feet in two directions. The 90-degree angle of the corner also could have been established using a right triangle, also called the sacred, or Pythagorean, triangle. In this kind of triangle a side of three units, four units, and five units yields a triangle with one 90-degree angle opposite the side of five units. Using this method, the sides could have extended 48 feet before the hypotenuse of the triangle disappeared into the base of the pyramid. Finally, the Egyptians could have established the right angle by drawing two intersecting arcs with a stick and string placed at any two points on the same line. Though this method would work approximately, it would be difficult not to stretch Egyptian string, thus reducing the accuracy of the operation.

Leveling . The final survey and alignment problem was leveling the base of the pyramid. Lehner has realized that the first course itself was used to establish the level platform rather than leveling the bedrock, as previous commentators believed. This method allowed for a perfectly level base.

Ramps . The final stones raised to the top of the Great Pyramid traveled 479 feet. Scholars have long agreed that some form of ramp was used to raise the stones to the upper courses and envisioned ramps running perpendicular and parallel to the sides of the pyramids. They also hypothesized that a ramp encircled the pyramid. Archaeological evidence suggests that there were some ramps perpendicular to the face of the pyramid, and in addition, others that wrapped around the structure.

Setting the Blocks and Controlling the Slope . A variety of methods were used to ensure that the four sides of the pyramid would meet evenly at the top and form a point. In Dynasty 3 (circa 2675-2625 b.c.e.) the walls were built of vertical layers that sloped toward the center. In Dynasty 4 (circa 2625-2500 b.c.e.) the walls were built of horizontal layers that were shaped to a slope on the outside edges. In Dynasty 5 (circa 2500-2350 b.c.e.) and 6 (circa 2350-2170 b.c.e.) the pyramids had rough cores with casing stones layered on the outside. Finally, in Dynasty 12 (circa 1938-1759 b.c.e.) the pyramids had mud-brick cores and outer casings.