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Workers pulling sled & pouring a liquid |
The Victorian Era discovery dates back to 1900 B.C., and shows 172 able-bodied men lugging a huge stone statue of the Middle Kingdom Pharaoh on a sledge with ropes attached to it. A person can be seen at the front of the contraption showering the sand with water. Egyptologists had thought that the reason ancient Egyptians had done this was for ceremonial reasons, but had never scientifically explained it. There has been great analysis and dialogue over exactly what the person is doing with the water and why. Now, however, the mystery may be solved of how ancient Egypt built the pyramids.
Researchers designed small-sized sledges and tried different ways of pulling them through sand. They found that when they pulled the sleds over the dry sand, the dirt piled up in front of the devices, creating berms in the sand and needing more effort to drag them. However, when they added water to it, the liquid made the surface stiffer, allowing the scientists to move the sledges easier. This is the key to the mystery of ancient Egypt built the Pyramids may be solved.
The droplets of water create bridge-like structures between the sand grains, allowing them to better fuse together. This is the very reason why building a sand castle with wet sand is better and easier. Keeping a perfect balance is key though; too much and the static friction gets weaker and weaker as more water is added to the equation, and to little creates berms in the sand that build up in front of the sled. The optimum amount depends on the sand, but is usually between 2 and five percent of the volume of material.
Apparently Egyptian sand is very good at reducing friction when it is wet. This makes it optimal for not needing a heavy workforce in order to move large materials a long way. The amount of force that is required to move extremely large objects could be cut in half and the threat of sand berms would virtually disappear. Experiments with the Egyptian sand showed that the needed force shrank in proportion to the sands rigidity, making it twice as firm as dry sand.
Researchers explain that this experiment not only solved the mystery of how ancient Egypt built the Pyramids, but also that sand stiffness is precisely linked to the friction force. The study may also have modern uses, such as understanding the ways of other granules. Knowing this may make the transport of other different types of granular materials like coal, concrete or asphalt more efficient.
Sources:Discovery NewsCBSNEWSThe Washington PostGIZMODO