The Great Pyramid of Giza (also known as the Pyramid of Khufu or the Pyramid of Cheops) is the oldest and largest of the three pyramids in the Giza pyramid complex bordering present-day El Giza, Egypt.

The Great Pyramid of Giza is the oldest of the Seven Wonders of the Ancient World, and the only one to remain largely intact.

Based on a mark in an interior chamber naming the work gang and a reference to the fourth dynasty Egyptian Pharaoh Khufu, some Egyptologists believe that the pyramid was thus built as a tomb over a 10- to 20-year period concluding around 2560 BC.

Initially, at 146.5 meters (481 feet), the Great Pyramid was the tallest man-made structure in the world for more than 3,800 years until Lincoln Cathedral was finished in 1311 AD.

Originally, the Great Pyramid was covered by limestone casing stones that formed a smooth outer surface; what is seen today is the underlying core structure. Some of the casing stones that once covered the structure can still be seen around the base.

There have been varying scientific and alternative theories about the Great Pyramid’s construction techniques. Most accepted construction hypotheses are based on the idea that it was built by moving huge stones from a quarry and dragging and lifting them into place.

There are three known chambers inside the Great Pyramid. The lowest chamber is cut into the bedrock upon which the pyramid was built and was unfinished. The so-called Queen’s Chamber and King’s Chamber are higher up within the pyramid structure.

The main part of the Giza complex is a set of buildings that included two mortuary temples in honour of Khufu (one close to the pyramid and one near the Nile), three smaller pyramids for Khufu’s wives, an even smaller “satellite” pyramid, a raised causeway connecting the two temples, and small mastaba tombs surrounding the pyramid for nobles.

History

Egyptologists believe the pyramid was built as a tomb for the Fourth Dynasty Egyptian pharaoh Khufu (often Hellenized as “Cheops”) and was constructed over a 20-year period.

Khufu’s vizier, Hemiunu is believed by some to be the architect of the Great Pyramid. It is thought that, at construction, the Great Pyramid was originally 280 Egyptian Royal cubits tall (146.5 meters (480.6 ft)), but with erosion and absence of its pyramidion, its present height is 138.8 metres (455.4 ft). Each base side was 440 cubits, 230.4 metres (755.9 ft) long.

The mass of the pyramid is estimated at 5.9 million tonnes. The volume, including an internal hillock, is roughly 2,500,000 cubic meters (88,000,000 cu ft).

Based on these estimates, building the pyramid in 20 years would involve installing approximately 800 tonnes of stone every day.

Additionally, since it consists of an estimated 2.3 million blocks, completing the building in 20 years would involve moving an average of more than 12 of the blocks into place each hour, day and night.

The first precision measurements of the pyramid were made by Egyptologist Sir Flinders Petrie in 1880–82 and published as The Pyramids and Temples of Gizeh. Almost all reports are based on his measurements. Many of the casing-stones and inner chamber blocks of the Great Pyramid fit together with extremely high precision.

Based on measurements taken on the north-eastern casing stones, the mean opening of the joints is only 0.5 millimeters (0.020 in) wide.

The pyramid remained the tallest man-made structure in the world for over 3,800 years, unsurpassed until the 160-meter-tall (520 ft) spire of Lincoln Cathedral was completed c. 1300.

The accuracy of the pyramid’s workmanship is such that the four sides of the base have an average error of only 58 millimeters in length. The base is horizontal and flat to within ±15 mm (0.6 in).

The sides of the square base are closely aligned to the four cardinal compass points (within four minutes of arc) based on true north, not magnetic north, and the finished base was squared to a mean corner error of only 12 seconds of arc.

The completed design dimensions, as suggested by Petrie’s survey and subsequent studies, are estimated to have originally been 280 Egyptian Royal cubits high by 440 cubits long at each of the four sides of its base.

The ratio of the perimeter to a height of 1760/280 Egyptian Royal cubits equates to 2π to an accuracy of better than 0.05 percent (corresponding to the well-known approximation of π as 22/7).

Some Egyptologists consider this to have been the result of deliberate design proportion. Verner wrote, “We can conclude that although the ancient Egyptians could not precisely define the value of π, in practice they used it”.

Petrie concluded:

“but these relations of areas and of circular ratio are so systematic that we should grant that they were in the builder’s design”.

Others have argued that the ancient Egyptians had no concept of pi and would not have thought to encode it in their monuments. They believe that the observed pyramid slope may be based on a simple seked slope choice alone, with no regard to the overall size and proportions of the finished building.

In 2013, rolls of papyrus called the Diary of Merer were discovered written by some of those who delivered limestone and other construction materials from Tora to Giza.

Construction theories

Many alternatives, often contradictory, theories have been proposed regarding the pyramid’s construction techniques.

Many disagree on whether the blocks were dragged, lifted, or even rolled into place. The Greeks believed that slave labor was used, but modern discoveries made at nearby workers’ camps associated with construction at Giza suggest that it was built instead by tens of thousands of skilled workers.

Verner posited that the labor was organized into a hierarchy, consisting of two gangs of 100,000 men, divided into five zaa or phyle of 20,000 men each, which may have been further divided according to the skills of the workers.

One mystery of the pyramid’s construction is its planning. John Romer suggests that they used the same method that had been used for earlier and later constructions, laying out parts of the plan on the ground at a 1-to-1 scale.

He writes that “such a working diagram would also serve to generate the architecture of the pyramid with precision unmatched by any other means”.

He also argues for a 14-year time-span for its construction. A modern construction management study, in association with Mark Lehner and other Egyptologists, estimated that the total project required an average workforce of about 14,500 people and a peak workforce of roughly 40,000.

Without the use of pulleys, wheels, or iron tools, they used critical path analysis methods, which suggest that the Great Pyramid was completed from start to finish in approximately 10 years.

The Big Void

In 2017, scientists from the ScanPyramids project discovered a large cavity above the Grand Gallery using muon radiography, which they called the “ScanPyramids Big Void“.

Its length is at least 30 meters (98 ft) and its cross-section is similar to that of the Grand Gallery. Its existence was confirmed by independent detection with three different technologies: nuclear emulsion films, scintillator hodoscopes, and gas detectors.

The purpose of the cavity is not known and it is not accessible but according to Zahi Hawass, it may have been a gap used in the construction of the Grand Gallery.

The Japanese research team disputes this, however, saying that the huge void is completely different from the construction spaces previously identified.

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*This article was originally published at en.wikipedia.org.