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By Aisling Irwin - Science Correspondent
Source: The Daily Telegraph newspaper, UK
Date: Friday 21st March 1997
One of the mysteries of the Egyptian Pyramids may have been solved by a Cambridge engineer, who claims that he knows how the builders managed to carry millions of heavy stones into position.
Egyptologists have always been impressed by the strength and diligence of the pyramid builders. The Great Pyramid at Giza, for example, required the quarrying and transporting of 2.3 million stones, each weighing about 2.5 tons.
Historians and engineers have suggested that the builders used sleds, ropes, levers, pulleys, cradle-like rockers and ramps. Evidence of all these survive, either physically or in pictures.
But Dr Dick Parry, a soil mechanics expert in the engineering department of Cambridge University, believes that none of the suggested methods could have worked. He calculated that the chosen method must have been efficient enough to put in place one block every few minutes if the Great Pyramid was built in 20 years, as he said was generally accepted.
He had rejected the principal suggestion that the Egyptians pulled the boulders on sleds up ramps that wound round the sides of the pyramid. This would have required between 60 and 80 men per sled - too many for the ramps to sustain, he argued.
"The ramp slopes would have had to be no flatter than one in four," he said. "It is recognised even by sled supports that you cannot pull a sled up a one in four slope."
Dr Parry also rejected the popular theory that the ancient Egyptians eased the blocks onto cradles which they rocked along. The method was too hazardous and could not cope with narrow pyramid steps, he added.
However, small models of these cradles have been discovered by archaeologists alongside model tools. Dr Parry told a Cambridge audience last night that he believed the cradles were used in a completely different way.
Four of them could be arranged to form a circular sheath around a block, transforming it from a cuboid into a cylinder. This would move easily on the level. To drag it uphill, the Egyptians could have coiled a long rope around the cylinder. As they pulled the block up the ramp the rope would gradually have uncoiled and the boulder would have rolled upwards, minimising the amount of human strength needed. Dr Parry was invited by Japanese engineering contractors to test his theory in Tokyo, using 2.5 ton blocks. He was delighted to find that the method worked, after some teething problems such as how to steer the system.
It took three men to push the block on the level - sled transport would have required 20 to 30 men. It took 16 to 20 men to pull it up a ramp with a one-in-four gradient. With a sled it would have taken 60 to 80 men - too many for the ramp structure.
The crucial test was whether about 20 men could pull it up a slope 49ft long in no more than five minutes - the constraints he believes the Egyptians must have worked under. They did it in one minute.
"I was pleased," he said. "I was pretty confident but you can never be 100 per cent sure about these things. This explains how they managed to place these blocks so rapidly."
Dr Ian Shaw, a specialist in ancient Egyptian technology at the Institute of Archaeology at University College London, said: "It is a very good idea for someone to have a stab at these nitty-gritty questions."
But he questioned how certain Dr Parry could be about some of the historical questions.
If the Great Pyramid took much longer than 20 years then other methods might have been possible," he said.
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