For centuries, people have theorized how the great pyramids of Egypt were built. The traditional perspective is that they were built through hauling massive stones across the sandy desert using just ropes, rolling logs, and manpower. However, many reject that claim and believe the Egyptians possessed a technology that has been lost through the ages. Now a new study claims they know the answer to the Egyptians’ architectural brilliance – wet sand.
According to the new study, published in the journal Physical Review Letters, ancient Egyptians used a simple trick to make the job of hauling heavy colossi easier – they moistened the sand before thousands of workers pulled the objects on a sledge.
“Liquid bridges start to form between the grains when water is added. Once there is enough water, these bridges act like glue, keeping the grains in place,” wrote the study authors, a multinational group of physicists led by Prof Daniel Bonn from the University of Amsterdam.
To test their hypothesis, the team of researchers placed a lab version of the Egyptian sledge in a tray of sand and measured the level of friction in dry versus wet sand. The results showed that the required pulling force decreased proportional to the stiffness of the sand.
New experiments show it is easier to drag an object over wet sand than dry sand. Credit: FOM
“Adding water made the sand more rigid, and the heaps decreased in size until no heap formed in front of the moving sled and therefore a lower applied force was needed to reach a steady state,” wrote the authors.
In support of the theory, a wall painting found within the tomb of Djehutihotep appears to depict a scene of slaves hauling a colossal statue of the Middle Kingdom ruler and in it, the scientists claim the person at the front of the sled is pouring liquid onto the sand.