Cairo: Scientists have uncovered one of the key methods Egyptians employed to move huge stones to build the pyramids - using wet sand!
The question of just how ancient Egyptians moved the two-tonne stones that made up their famed pyramids without the help of modern technology has long plagued scientists.
Physicists from the Fundamental Research on Matter (FOM) and the University of Amsterdam have now discovered that the ancient Egyptians moistened the sand over which the sledge moved.
By using the right quantity of water they could halve the number of workers needed, researchers said.
For the construction of the pyramids, the ancient Egyptians had to transport heavy blocks of stone and large statues across the desert.
They therefore placed the heavy objects on a sledge that workers pulled over the sand.
The new study has shown that the Egyptians probably made the desert sand in front of the sledge wet. Experiments have demonstrated that the correct amount of dampness in the sand halves the pulling force required.
The physicists placed a laboratory version of the Egyptian sledge in a tray of sand.
They determined both the required pulling force and the stiffness of the sand as a function of the quantity of water in the sand.
To determine the stiffness they used a rheometer, which shows how much force is needed to deform a certain volume of sand.
Experiments revealed that the required pulling force decreased proportional to the stiffness of the sand. Capillary bridges arise when water is added to the sand. These are small water droplets that bind the sand grains together.
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 probably aware of this handy trick. A wall painting in the tomb of Djehutihotep clearly shows a person standing on the front of the pulled sledge and pouring water over the sand just in front of it.
The research was published in the journal Physical Review Letters.