Virtual Handout for Discussion in Dr. Scott Johnson's Introductory Engineering Class
History of Engineering: Building the Pyramids
One of the greatest feats of ancient engineering was the building of the great pyramids. While the pyramid structure is found in many cultures(Mesopotamia's ziggurats, Mesoamerica's pyramid, North America's pyramid-shaped mounds, China's flat-top pyramid, etc.), the great pyramids of Egypt captivate the imagination more than any other. The great pyramids of Egypt are over 145 meters tall dwarfing the Statue of Liberty in height (just a bit smaller than the Washington Monument which is 169 meters tall. Their base length is over 230 meters and they are estimated to have more than two million blocks of stone with the average weight of one of those stone being approximately 2.3 metric tons.
The pyramid structure seems to have originated from mastabas in Nubia. The stepped mastaba (Arabic for a type of bench) appeared around the Third Dynasty (2650-2575 BCE) in ancient Egypt and look very much like a true pyramid. These "pyramids" were surrounded by a number of other structures associated with the pyramids function. Sometime between the Third and Forth Dynasty a number of attempts were made to convert stepped mastabas into true pyramids. The conversion from a stepped mastaba to a true pyramid did have a number of failures, but the Egyptian engineers would work around the problems or in the case of complete failure note the problems and re-design avoiding the reason for failure. The great pyramids were built in the Forth and Fifth Dynasties using idle laborers1 during the flooding season. These pyramids are testament to the success of their engineering designs. Besides the great pyramids there are approximately 118 pyramids in Egypt and 200 pyramids in the Sudan (Nubia). Likely a team of engineers and specialized workers had to be employed full time working on the pyramid construction during these Dynasties.
In the above figure from the eternal egypt web site you see the bent pyramid which needed to be corrected in the middle of the project.
Building a pyramid required a good grasp of mathematics, geometry, and knowledge of the qualities of the available materials. The design and positioning of the pyramids were very precise. The great pyramids are perfectly situated to have their sides line up to north, south, east, and west. The accuracy is uncanny for the time period. It is likely this was achieved by accurately observing the north star and using a plumb line. Other geometrical techniques were used to assure that the pyramid's edges would align at the apex.
In the above figure from Ancient Egyptian Construction and Architecture we see an architect's diagram using skilled mathematical techniques.
To build a pyramid the land had to be surveyed for a relatively flat area above the flood plain covering an area greater than the size of the proposed pyramid. Taking into consideration the enormous load to be placed on the proposed site, the bedrock had to be surveyed for defects to ensure a stable foundation. This is the type of job a civil engineer would do today.
After a site was designated it would be prepared by leveling off the rock foundation. Building would begin on this prepared site. In Egypt measurements were generally done using body parts. The standard unit of measure was the cubit which was a length from the elbow to the tip of the middle finger. For basic sort of work this measurement was sufficient, but for the great pyramids the royal cubit was used. This measured 52.5 cm and would normally be represented by a rod. The pyramid's base was design to be almost perfectly square using the rod as a measuring tool.
In building any structure to have level surfaces is extremely important. Egyptians developed levels using the force of gravity called a plumb level which is an application of the well-known plumb line. Plumb lines are still used today just as in ancient Egypt.
In the above figure from the eternal egypt web site you see the plumb level of Sennedjem. This tool was used to ensure a level vertical surface.
Most of the large stone blocks of the great pyramids where of low quality limestone, however the internal chambers and hallways used granite, and the pyramid was encased in a fine limestone. This encasement was polished to give the great pyramids a spectacular white appearance. The majority of the blocks to build the pyramid where quarried right next to the pyramids. Giza was chosen partly because of the good building materials in the area.
In the above figure from Ancient Egyptian Construction and Architecture we see the clear evidence of blocks being removed from near the pyramids.
Blocks were moved using sleds with water (or possibly oil) poured underneath. The blocks were taken up the pyramid using ramps of mud brick and rubble. While ancient Egyptians used ropes and levers there is no evidence of the use of pulleys. Even if they had knowledge of pulleys it is unclear if a block and tackle of sufficient strength could be made to move such large blocks. Ropes and levers were used to position in certain instances as well.
In the above figure from Ancient Egyptian Construction and Architecture we see a heavy object (in this case a statute) being moved by sled with a working pouring water in the front of the sled.
Mortar was used for settling the stones but not for cement as might be used today. The mortar, made of gypsum (plaster and sand), was very soft like butter. The advantages of gypsum mortar is that it is slow-setting and, while it is setting, it can act as a sort of lubricant to lessen the friction between large blocks. Gypsum mortar is still used for certain construction (in dry environments or internal structures) in modern times. Rockers were used for placement of the blocks while the gypsum mortar sets when careful placement was necessary.
As the building of the pyramid progressed ramps would be placed along side the edges of the pyramid to allow the workers using sleds to drag the large blocks up the ramps. New evidence suggests ramps might have been inside the pyramid as it was built as well. The outside ramps would be removed after their usefulness was at an end. After completion a limestone covering was placed on the pyramid as stated above. These coverings have all but dissolved today.
The building of the great pyramids of Egypt took an accumulation of knowledge, testing, and creative engineering. The Great Pyramid of Giza is one of the largest pyramids in the world and was the tallest structure in the world until the beginning of the renaissance in Europe many thousands of years after their construction. It along with the great pyramids of Mesoamerica are a testament to the ability of engineers to create grand structures and stretch our horizons. In modern times the Egyptian pyramids captivate the imagination of engineers and spur them to reach new heights as far as the moon and beyond.
The Giza pyramids from a Department of Defense photo
Aerial photograph from 1904 of the pyramids of Giza taken on a balloon by Eduard Spelterini
The Giza pyramids from a Department of Defense photo at a different angle.
In the above figure from Wikipedia: Author: MesserWoland we see the full extent of the cemetery of the great pyramids.
To further investigations, I suggest the following books and websites:
When the Pyramids were Built: Egyptian Art of the Old Kingdom, Dorothea Arnold, The Metropolitan Museum of Art, New York (1999)
Egyptology: An Introduction to the History, Culture and Art of Ancient Egypt, James Putnam, Crescent Books, New York (1990)
Ancient Egyptian Construction and Architecture, Somers Clarke and R. Engelback, Dover Publications, Inc., New York (1990)
Eternal Egypt, Egyptian Center for Documentation of Cultural and Natural Heritage and IBM, http://www.externalegypt.org
Dr. Zahi Hawass, One of the most famous modern Egyptologists,http://www.drhawass.com
Dr. Kara Cooney, Young new Egyptologist who is very media savvy,http://www.karacooney.squarespace.com/
1Slaves were not used in building in Egypt. The story of slavery in Egypt might have originated from ancient Greece writings that were inaccurate. Herodotus certainly claimed this, but he said he was told this and it was many many years after the construction of the pyramids.