Monday, August 4, 2008

Great Pyramid of Cheops

In the western suburbs of modern Cairo, 130 feet above the Nile, stands a 1-mile (1.6-kilometer) square artificial rocky plateau called Giza (El-Jizah) by the Arabs. It is the site of three Fourth Dynasty pyramid tombs—Cheops’, Chephren’s, and Mycerinus’s—named by the ancients among the seven wonders of the world. The largest of them, built at the command of Cheops, has been called a “unique monument” because of its internal disposition. While it is clearly part of an evolving architectural type, there is little doubt that in terms of engineering and logistics, this so-called Great Pyramid was a superlative achievement.

Cheops, also known as Khufu (Khnum-Khufwy, “Protected by Khnum”), was the second king of the Fourth Dynasty and reigned from 2589 to 2566 b.c. Although little is known of him, he is believed by some scholars to have been a tyrannical and cruel ruler. Whatever the case, clearly he was able to lead and coordinate, because the building of his tomb involved sophisticated social planning to harness an immense team of workers, both on and off the site, together with all the backup resources needed for such a daunting task. The fifth-century-b.c. Greek historian Herodotus calculated that 100,000 slaves would have taken 30 years to build the Great Pyramid. But it was not constructed by slave labor; rather, Egypt’s peasant farmers, displaced from July through November when their fields were inundated by the annual flooding of the Nile, were deployed on the project, as well as on other public works. The cost of their food and shelter (there were workers’ villages built nearby) was met from their own surplus production, levied as taxes. Modern scholarship suggests that only 20,000 men could have completed Cheops’ tomb in only 20 years.

The base of the Great Pyramid (Akhet Cheops, the Horizon of Cheops), oriented within 0.3 minute of accuracy to the cardinal compass points, is 756 feet (230.5 meters) square, covering 13 acres (5.2 hectares). The extensive base means that the tremendous weight of the tall 479-foot (146-meter) building, amounting to an estimated 6.99 million tons (6.35 million tonnes), does not overload the foundation; it is also very stable because its center of gravity is very low. Although of simple design, such an engineering feat challenges even the modern imagination. The pyramid is estimated to contain 2.5 million limestone blocks, each weighing anything from 3 to 17.7 tons (2.5 to 15 tonnes), rising in 200 steps to the height of a 40-story office block. The joints between the blocks are about 0.02 inch (0.5 millimeter). As originally designed, the pyramid was encased in a 16-foot-thick (5-meter) layer of polished white limestone won from the quarries at Tura, east of the Nile. Most of it was plundered in the sixteenth century and used to build mosques in Cairo. At the pinnacle of the Great Pyramid there was a solid capstone of polished Aswan granite, standing on a 33-foot (10-meter) square platform.

All this, from quarrying to setting the stones, was achieved with copper and stone tools. Barges were used to transport blocks from a quarry on the far side of the Nile. How were they raised as the pyramid progressed? It is thought that ramped causeways, lubricated with water, were used to haul the sleds; these may have been built at different levels on each side of the pyramid, or a single ramp may have wound around the whole structure as it rose. While oxen were used to move stone blocks in the quarry, the accuracy demanded on-site required wooden sleds hauled by men, and fewer than ten were needed to maneuver a block into place using wooden rockers.

For all the looming size of the Great Pyramid, its interior spaces are relatively tiny. An entrance passage—not the original—connects with a narrow, 345-foot-long (105-meter) descending passage that leads to a 46-by-27-foot (14-by-8.3-meter) subterranean room, a little over 11 feet (3.5 meters) high. It has been suggested that this was the first location chosen for Cheops’ burial chamber; that was quickly abandoned, probably on theological grounds. From the junction of the two passages, a 129-foot-long (39-meter) ascending passage leads to the outer end of the “great gallery.” From that point, a horizontal corridor gives access to the so-called Queen’s Chamber, vaulted with inclined blocks; a second alternative burial chamber, it was never completed and never used. The 154-foot-long, 28-foot-high (47-by-8.5-meter) great gallery, with a finely crafted corbel vaulted ceiling, leads upward to the final location of the King’s Chamber, built of pink Aswan granite. The chamber still contains the huge red granite sarcophagus that must have been put in place while the pyramid was being built. Above it a series of five relieving chambers distributes the weight of the structure above away from the chamber. There are two shafts sealed at the extremities, through which the king’s ka (spirit) could come and go from the underworld.

Several ancillary buildings were associated with Cheops’ pyramid. Members of the royal family were buried in mastaba tombs, and three small pyramids to the east were probably for his sister-wife, Merites, and perhaps other queens. Nobles and courtiers were interred in the royal cemetery to the west of the Great Pyramid, where there were also funerary temples and processional ramps. All that remains of Cheops’ Mortuary Temple is some of the basalt paving.

Since the early 1990s, there have been serious attempts to preserve the fabric of the Great Pyramid. It was restored in 1992. Recurring salt deposits, cracking, spalling of the limestone, and the appearance of black spots, all resulting from increases in humidity and carbon dioxide caused by large numbers of tourists, necessitated further action. Early in 1998 the building was closed to the public while a more efficient mechanical ventilation system was installed. It changes the air every 45 minutes, employing the original ka shafts from the King’s Chamber as exhaust ducts and drawing fresh air through the access passage. The number of daily visitors has been severely limited and airlines have been warned of a “no-fly” zone above the site.

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