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Researchers have uncovered one of the key methods the Egyptians used to build the pyramids.

They have long been baffled by exactly how workers were able to transport large blocks of stone to construction sites.

Now, they say the key was simple - wet sand.

Researchers say the key to building the pyramids was wet sand. The Egyptians placed the heavy objects on a sledge that workers pulled over the sand specially dampened

HOW THEY DID IT

The physicists placed a laboratory version of the Egyptian sledge in a tray of sand (pictured).

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.

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.

'For the construction of the pyramids, the ancient Egyptians had to transport heavy blocks of stone and large statues across the desert,' researchers at the University of Amsterdam said.

The team tried to replicate this - and found wet sand was the key.

The Egyptians therefore placed the heavy objects on a sledge that workers pulled over the sand.

Research from the University of Amsterdam has now revealed 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.

To test the theory, 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.

'In the presence of the correct quantity of water, wet desert sand is about twice as stiff as dry sand, the team said.

A wall painting from the tomb of Djehutihotep, showing a large statue is transported by sledge, while a person standing on the front of the sledge wets the 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 also believe a painting reveals the trick.

'The Egyptians were probably aware of this handy trick,' they said

'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 results could therefore be useful for examining how to optimise the transport and processing of granular material, which at present accounts for about ten percent of the worldwide energy consumption.

The team say sand that was 'just right' was key to the sled's ability to move to the construction sites