For the creation of the pyramids, prehistoric Egyptians had to move heavy masses of stone and large statues through the desert. They put the heavy objects on a sled that workers dragged over the sand. A worldwide group of physicists directed by Prof Daniel Bonn from the University of Amsterdam has theorized that Egyptians possibly made the desert sand ahead of the sledge wet. To check their hypothesis, fellows of the team placed a lab form of the Egyptian sledge in a tray of sand. They determined both the essential pulling force and the stiffness of the sand as a function of the amount of water in the sand. To conclude the stiffness they used a rheometer, which displays how much force is required to warp a certain volume of sand.
Sketch of a wall painting from the tomb of Djehutihotep, a semi-feudal leader of an Ancient Egyptian region, 1880 BC. A person standing at the front of the sledge is pouring water onto the sand.
The outcomes show that the necessary pulling force reduced proportional to the stiffness of the sand. Capillary bridges rise when water is added to the sand. These are minor water droplets that bind the sand grains together.
The researchers said “In the presence of the correct quantity of water, wet desert sand is about twice as stiff as dry sand. A sledge glides far more easily over firm desert sand simply because the sand does not pile up in front of the sledge as it does in the case of dry sand,” The Egyptians were possibly aware of this handy trick. A wall picture in the tomb of Djehutihotep noticeably displays a person standing on the front of the dragged sledge and pouring water over the sand right in front of it. “Besides revealing something about the ancient Egyptians, the results are also interesting for modern-day applications. We still do not fully understand the behavior of granular material like sand. Granular materials are, however, very common. Other examples are asphalt, concrete and coal.”
“The research results could therefore be useful for examining how to optimize the transport and processing of granular material, which at present accounts for about ten percent of the worldwide energy consumption.”
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