The Aztecs, Mayans and ancient Egyptians were three very different civilizations with one very large similarity: pyramids. However, of these three ancient cultures, the Egyptians set the standard for what most people recognize as classic pyramid design: massive monuments with a square base and four smooth-sided triangular sides, rising to a point. (The Aztecs and Mayans built their pyramids with tiered steps and a flat top.)
The ancient Egyptians probably chose that distinctive form for their pharaohs' tombs because of their solar religion, explains Donald Redford, professor of classics and ancient Mediterranean studies at Penn State. The Egyptian sun god Ra, considered the father of all pharaohs, was said to have sat upon a pyramid-shaped mound of earth which had emerged from the primordial sea. The pyramid's shape is thought to have symbolized the sun's rays.
According to Redford, "The Egyptians began using the pyramid form shortly after 2700 B.C., and the great heyday of constructing them for royalty extended for about a thousand years, until about 1700 B.C." The first pyramid was built by King Djoser during Egypt's Third Dynasty. His architect, Imohtep, created a step pyramid by stacking six mastabas, rectangular buildings of the sort in which earlier kings had been buried. The largest and most well-known pyramids in Egypt are the Pyramids at Giza, including the Great Pyramid of Giza designed for Pharaoh Khufu.
For centuries, people have theorized how the great pyramids were built. Some have suggested that they must have been constructed by extraterrestrials, while others believe the Egyptians possessed a technology that has been lost through the ages.
But the process of building pyramids, while complicated, was not as colossal an undertaking as many of us believe, Redford says. Estimates suggest that between 20,000 and 30,000 laborers were needed to build the Great Pyramid at Giza in less than 23 years. By comparison, Notre Dame Cathedral in Paris took almost two hundred years to complete.
According to Redford, pharaohs traditionally began building their pyramids as soon as they took the throne. The pharaoh would first establish an "engineering department" composed of an overseer of all the king's construction work, a chief engineer, and an architect, as well as, in effect, a "department of manpower." The pyramids were usually placed on the western side of the Nile because the pharaoh's soul was meant to join with the sun disc during its descent before continuing with the sun in its eternal round. The two deciding factors when choosing a building site were its orientation to the western horizon where the sun set and the proximity to Memphis, the central city of ancient Egypt.
The cores of the pyramids were often composed of local limestone, says Redford. Finer quality limestone composed the outer layer of the pyramids, giving them a white sheen that could be seen from miles away. The capstone was usually made of granite, basalt, or another very hard stone and could be plated with gold, silver, or electrum (an alloy of gold and silver) and would also be highly reflective in the bright sun.
The image most people have of slaves being forced to build the pyramids against their will is incorrect, Redford says. "The concept of slavery is a very complicated problem in ancient Egypt," he points out, "because the legal aspects of indentured servitude and slavery were very complicated." The peasants who worked on the pyramids were given tax breaks and were taken to 'pyramid cities' where they were given shelter, food and clothing.
According to Redford, ancient Egyptian quarrying methods—the processes for cutting and removing stone—are still being studied. Scholars have found evidence that copper chisels were used for quarrying sandstone and limestone, for example, but harder stones such as granite and diorite would have required stronger materials. Dolerite, a hard, black igneous rock, was used in the quarries of Aswan to remove granite.
During excavation, massive dolerite "pounders" were used to pulverize the stone around the edge of the granite block that needed to be extracted. According to Redford, 60 to 70 men would pound out the stone. At the bottom, they rammed wooden pegs into slots they had cut, and filled the slots with water. The pegs would expand, splitting the stone, and the block was then slid down onto a waiting boat.
Teams of oxen or manpower were used to drag the stones on a prepared slipway that was lubricated with oil. Redford notes that a scene from a 19th century B.C. tomb in Middle Egypt depicts "an alabaster statue 20 feet high pulled by 173 men on 4 ropes with a man lubricating the slipway as the pulling went on."
Once the stones were at the construction site, ramps were built to get them into place on the pyramid. These ramps were made of mud brick and coated with chips of plaster to harden the surface. They were "wrap-around" style, rather than straight, Redford says, "because in laying the upper layers of a great pyramid, the gradient necessary for a straight ramp would be impossible."
"If they consistently raised the ramp course by course as the teams dragged their blocks up, they could have gotten them into place fairly easily," Redford explains, adding that at least one such ramp still exists today.
When answering to skepticism about how such heavy stones could have been moved without machinery, Redford says, "I usually show the skeptic a picture of 20 of my workers at an archaeological dig site pulling up a two-and-a-half ton granite block. I know it's possible because I was on the ropes, too."
Donald B. Redford, Ph.D., is professor in the Department of Classics and Mediterranean Studies, and can be reached at firstname.lastname@example.org.
Editor's Note: This story has been updated since its original publication in 2008.
Since 2015, Dr. Tayoubi and his colleagues, now consisting of three separate teams of physicists and engineers, have investigated the pyramid using a particle physics technique known as muon tomography to see through to its core.
“We tried to do for the pyramid what a doctor can do with X-rays,” Dr. Tayoubi said.
Instead of X-rays, the team used muons, the heavy cousins of electrons that form when cosmic rays from outer space collide with particles in Earth’s atmosphere. The fallout from the collisions creates a constant bombardment of harmless particles that can penetrate deep into the planet. As the muons pass through matter they lose energy and decay, so if the team detected a small number of muons, that means they were passing through matter. But if they detected more muons, it suggests the particles were passing through empty space or less dense material.
The technology was previously used by Luis Alvarez, a Nobel Prize-winning physicist, to investigate whether there were hidden chambers in the Pyramid of Khafre in the 1960s. As muon detector resolution has greatly improved over the decades, it has since been used to see the inner structures of volcanoes as well as the irradiated Fukushima nuclear reactor.
In 2016, Dr. Tayoubi’s colleagues stood in the Queen’s chamber and used muon detectors capable of making improved measurements to study particles as they passed through the pyramid. When they analyzed their data from a region above the Grand Gallery, a long inclined passageway that leads to the King’s Chamber, they found something strange: an unexpected excess of muons.
They found a void.
The first measurements were made by researchers from Nagoya University in Japan who were a part of the project. Then two more teams associated with ScanPyramids, one from France and another from Japan, also confirmed the anomaly with muon tomography, even from outside the pyramid. The discovery comes on the footsteps of the team’s previous work, which detected a small void behind the north face of the pyramid in 2016.
Christopher Morris, a physicist who conducts research using muon tomography at Los Alamos National Laboratory and was not involved in the study, called the findings “pretty amazing,” adding that all the team needed to do was set up their muon detectors and reap the rewards.
“All the other physicists who could have done it, and didn’t, are jealous,” he said.
Arturo Menchaca-Rocha, a physicist from the National Autonomous University of Mexico who has used muon detection to investigate the Pyramid of the Sun in Mexico, echoed Dr. Morris’s sentiments and said the project’s physics supported its claims.
But archaeologists were more critical of the work.
Mark Lehner, an Egyptologist from Ancient Egypt Research Associates, said that previous work had shown that the ancient Egyptians most likely constructed gaps in their pyramids and that the voids the team found are nothing special, or new.
“The great pyramid of Khufu is more Swiss cheese than cheddar,” he said. He added that the steep incline of the void also casts doubts on whether it was some sort of room. “At that angle, it doesn’t make much sense for it to be a chamber that would contain artifacts, burials and objects and that sort of thing.”
Zahi Hawass, an Egyptologist, former Egyptian government minister and head of the scientific committee appointed by the Egyptian Ministry of Antiquities to review the work, was more critical of the finding.
“They found nothing,” said Dr. Hawass, noting that such construction gaps had been known of for at least two decades. “This paper offers nothing to Egyptology. Zero.”
Both Dr. Lehner and Dr. Hawass agreed that the scanning work should continue in hopes that the teams can retrieve higher resolution data about the inner workings of the pyramid, specifically the shape and size of the anomaly.
Hany Helal, who is also a co-director of the ScanPyramids project, responded to the criticism, saying that from an engineering perspective, it would not make sense to have such a big void above the Gallery if its purpose was to relieve pressure.
He said the next steps are to have an international discussion with archaeologists to figure out the structure’s purpose. In the future, he added that scientists may use drones to explore the void once they have more information about it.
“We are sure there is a void,” he said. “Now let us continue our research.”Continue reading the main story