How the ancient Egyptians managed to move multi-ton stones to build the pyramids without modern technology has long baffled scientists, but now researchers think they’ve learned the secret.
According to the American Physical Society, a team from the University of Amsterdam showedthat adding water — but not too much — to sand would reduce friction enough to make sliding an object on it easier.
In this Egyptian painting, the researchers pointed out that it shows a sled with water being poured in front of it. (Image source: University of Amsterdam/Fundamental Research on Matter)
The physicists conducted an experiment that showed how “capillary water bridges” formed with the addition of water, aiding in sliding. Too much water, however, would actually increase sliding friction.
“Our results, therefore, show that the friction coefficient is directly related to the shear modulus; this has important repercussions for the transport of granular materials. In addition, the polydispersity of the sand is shown to also have a large effect on the friction coefficient,” the authors wrote of the technical details in the abstract for the study published in Physical Review Letters.