Kennislink reported at the beginning of this month about physics research showing that the tensile force halves when sand is wetted. The Ancient Egyptians would have used that trick to make it easier to transport pyramid stones. But according to two professors from KU Leuven, that is nonsense.
How could the Ancient Egyptians make such imposing structures as the pyramids? Scientists have been pondering this question for some time. Research by Professor of Physics Daniel Bonn (University of Amsterdam) recently showed that wet sand makes it much easier to transport heavy statues and stones and that the Ancient Egyptians made use of it. But Egyptologist Harco Willems and physical geographer Gert Verstraeten (both KU Leuven) dispute that conclusion.
Mud
Bonn did an experiment in a lab where he pulled a sled with weights over dry, wet and very wet sand. His conclusion was that sand that is slightly wet has the least resistance. “It must be true that wet, granular sand has less resistance than dry sand,” says Willems, who studies transport routes in Ancient Egypt. “But Bonn should also have examined mud. The current Egyptological hypothesis that heavy loads were pulled over a road surface of wet silt is not disproved by his experiments. Mud is smoother than wet sand. It's not for nothing that you slip even faster.”
When asked, Bonn says that it has indeed tested mud. “Mud gives a resistance that is twice as high as wet sand,” he says. “We made sand very wet.” But that, according to Willems, is not the correct way. “He has to get mud from a river, like the Nile. Because that is most likely the mud that the Ancient Egyptians used, because in a number of cases we found it in ancient road surfaces.”
According to Bonn, it is impossible for a physics research to experiment with this. “All the details are important. What is the exact composition, where does it come from?” Friction is a very difficult problem to investigate, Bonn points out. He did the same test as with the sand on the braking resistance of car tires. “But that turned out to be much more difficult, especially due to different types of rubber. The same is true with mud. How do you know for sure what kind of mud you are researching and whether the Egyptians used it? That mud works better is not based on a physics experiment.”
Mystery
Willems agrees that it is extremely difficult to determine what kind of mud was used. “That is exactly the problem and that is precisely why Bonn should have researched mud from Egypt, otherwise his research says nothing about Ancient Egypt. Only then is it serious archaeological research.” Willems' research shows that the Ancient Egyptians built mud paths themselves. For example on sand or after they first made the ground solid with wooden sleepers or stones.
At the grave of Governor Djehutihotep, the latter was not even necessary. Bonn used a tomb painting as an example for his research on wet sand. On it, Egyptians carry a colossal statue. Someone wets the sand in front of the statue. Willems is well acquainted with the grave and transport, because he does excavations there. "The subsoil there is quite hard, a mixture of sand and marl, among other things. There is no granular sand there, as Bonn describes in his research.
It also doesn't do much if you just wet the surface. Bonn should have taken that into account. In the vicinity of the pyramids and where the stone material came from, there was not much pure sand either. There we found transport routes for sleepers with different material and mud on them."
Bonn does not agree that Willems and Verstraeten tell him how to do his research. He emphasizes that he has done a physics experiment. “I was given the idea by an Egyptologist and so I thought it might be interesting for Egyptologists. But I didn't pretend to do an Egyptology study. I am told several times how I should have done it differently to make it relevant to research on ancient Egypt. But that was not my goal.”
Bonn thinks it is good that this subject is being discussed. “But I'm disappointed with the way it is. Willems and Verstraeten state that I carried out the investigation carelessly. That is not true. I would like to talk to them and invite them to discuss this further.”
Willems emphasizes that the mystery surrounding the transport and construction of pyramids has still not been solved. “Every year there are publications full of theories. But we don't know exactly how they were built. They were probably dragged up, but we're not entirely sure. The exact transport to the construction sites also remains unclear. So the mystery is still there.”