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Physicist says Ancient Egyptians used wet sand to move multi-ton pyramid stones

Earlier today, the Huffington Post reported that the hotly-debated subject of how the Egyptians managed to move the several-ton stones used to make the pyramids. While researchers in the past have attempted to recreate the feat, they were always overwhelmed by the substantial friction caused by sand building up in front of the massive stones. The new theory is that the Egyptians used water to reduce both friction and needed manpower.

Could wet sand solve the mystery of how the pyramids were built?
Photo by Jeff J Mitchell/Getty Images

Physicist Daniel Bonn, based out of The University of Amsterdam, developed the theory after observing an ancient Egyptian painting depicting a worker pouring water onto the sand in front of a wooden sledge. Although wetting sand has long been viewed by archaeologists as some kind of religious ritual, Bonn believes this assumption to be false.

Even children playing in the sandbox are able to observe that dry sand doesn't stick together but that wet sand will hold it's shape. Bonn says that pouring the right amount of water onto the sand in front of the sledges used to haul pyramid stones would form a road or “bridge” and the wet sand would stay in place.

Bonn created a study in which he and his team created a miniature version of an Egyptian sledge, placed it in “a tray of sand” and performed several trials on both wet and dry sand using weights ranging from 100 grams to a few kilograms. The results were easy to predict. The sledge pulled on dry sand took “a relatively high force” to reach a steady speed, and the sand piled up in front of it. When pulled on more stable wet sand, the heaps were not as large and “decreased in size until no heap formed in front of the moving sled.” Bonn and his team estimate that wetting the sand would allow the Egyptians to use half as many laborers as previously estimated.

Bonn says that the jar in the painting is the same type of jar archaeologists have established was used to carry water, making it unlikely the liquid portrayed in the jar is any other kind of lubricant. Mark Lehner, director of Ancient Egypt Research Associates, is intrigued by the idea, but believes the Egyptians methods for moving the giant limestone blocks were a bit more complex.

Lehner observed a fine layer of desert clay beneath some blocks which were abandoned on route to the construction site. Lehner hypothesized that the wet sand could have been used for moving the blocks over long stretches of desert, but he is certain that desert clay, called talfa, and gypsum mortar were used for finer movements and final placement of the stones.