More than 4,000 years ago, a minority of ancient Egyptians set a majority to work building some of the oldest human-made structures in the world. It seems like we've been debating about how they did it ever since: Water? Animal labour? Magic? A team of researchers thinks they've found the best explanation yet.
In a paper called How they (should have) built the pyramids, three scientists at Indiana State University explain how they came up with a brilliant method for moving huge, heavy stones. You'd never imagine that the cubic blocks of stone, freshly cut from the quarry and weighing in at 2.5 tonnes, would be rollable.
But what if these blocks weren't four-sided? What if, by strapping three long wooden rods to each face, you could turn them into a 12-sided dodecagon, making them much easier to "roll" along the surface?
The team explains:
Rolling a prism of 4 sides is not efficient, but adding wooden rods to the surface can effectively increase the number of sides. The crew can then pull on a rope wrapped around and passing over the top of the block. In this configuration, static friction acts in the direction of the desired motion, rather than opposing the motion.
It's as simple as it is smart, and the team even tested it out on a scale model to prove it.
Now, there's no archaeological evidence to suggest that this method was the one used. But it's definitely just as plausible as any other explanation that's been floating around these past few centuries.
In some ways, it makes even more sense. Back in March, another paper explained how the pyramid-destined stones were moved on sledges across the sand, with help from the capillary bridges created by water put down in front of the cart. But as the Physics ArXiv blog points out today, some pyramids are quite far away from sources of easy water. This rolling method would explain how those sites got their blocks.
Sadly, we'll probably never be able to say, for sure, what built the pyramids. But in some ways, it makes the endless debate over how even more fun. [Physics arXiv Blog]
Lead image: Dudarev Mikhail