A wall painting from 1880 BC shows a figure standing at the front of a sled
and pouring water onto the sand. Image courtesy of Physical Review Letters.
The great Egyptian pyramids have made visitors scratch their heads for millennia: How did the builders move such huge stones into place?
When Herodotus, the Greek historian, was visiting Egypt in the 5th century BC, he was told that the quarried stones were carried over the river by boat, “and they worked by a hundred thousand men at a time, for each three months continually.” From the river the stones were dragged to the building site.
Some in the 20th century found the building of the pyramids humanly impossible and have suggested aliens did it.
But now physicists from the University of Amsterdam and the Foundation for Fundamental Research on Matter say Herodotus was nearer to the answer. The stones were dragged across the land, according to the study in Physical Review Letters, with just the right amount of water.
If sand is wet, the researchers say, it becomes much easier to drag a sled carrying a heavy stone.