May 2, 2014
Secrets Of The Ancient Egyptians’ Stone Transport System Revealed
Lawrence LeBlond for redOrbit.com - Your Universe Online
Studying the Egyptian pyramids long enough may make one wonder how the massive stones were moved across the arid sands thousands of years ago. According to new research from the University of Amsterdam (UVA) and the FOM Foundation, stones and other objects were transported via sledge using a clever technique: moistening the sand.The study, published in the journal Physical Review Letters, finds that by adding just the right amount of water to sand, liquid bridges begin to form that make it easier to transport heavy objects across otherwise difficult-to-use sand. Similarly, building sandcastles at the beach require just the right amount of water to make the sand stick together – not enough and the sand slumps apart; too much and the sand turns to mud.
The researchers said that by using the right amount of water to transport the heavy stones could reduce the number of workers needed to pull the stones across the desert by as much as half. To pull the stones and statues across the desert, workers placed them on a sledge. By adding the right amount of water to the sand, enough force was created to pull the stones easily.
The researchers said it is likely that one ancient worker would stand at the front of the sledge and moisten the sand as workers pulled it. Evidence of this is seen in a wall painting found in the tomb of Djehutihotep that clearly shows a person standing on the front of sledge pouring water over the sand as workers pulled a massive statue.
For the study, the research team placed a laboratory version of the Egyptian sledge in a tray of sand and used a rheometer to determine how much force was needed to deform a certain volume of sand in order to pull the sledge easily – in essence, they determined both the pulling force and the stiffness of the sand based on the amount of water used. Their experiments revealed that the required pulling force decreased proportional to the stiffness of the sand.
When water is added to sand, capillary bridges begin to form that bind the sand grains together. With the correct amount of water, wet desert sand is about twice as stiff as dry sand. The sledge in the lab experiment glided far more easily over firm desert sand simply because the sand did not pile up in front of the sledge as it does when it is dry.
The experiment not only reveals how the ancient Egyptians likely moved massive structures across the arid desert, but the results have implications for modern-day applications as well. The behavior of granular material like sand is still not fully understood, despite the commonness of such material. Other examples of granular material are asphalt, concrete and coal.
The team, supervised by Daniel Bonn, group leader for the FOM Foundation and director of the UVA Institute of Physics, said the results of their study could be useful for examining how to optimize the transport and processing of granular material, which accounts for about 10 percent of the worldwide energy consumption.
(Left Image): A large statue is being transported by sledge. A person standing on the front of the sledge wets the sand. Source: Al-Ahram Weekly, 5-11 August 2004, issue 702. Credit: Fundamental Research on Matter (FOM)
(Right Image): A large pile of sand accumulates in front of the sledge when this is pulled over dry sand (left). On the wet sand (right) this does not happen. Credit: Fundamental Research on Matter (FOM)