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this post was submitted on 18 May 2024
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I swear that I'm not trying to be obtuse, but I have a lot of doubts.
What kind of ropes and wooden sleds, manufactured in 4000 BC, can move 80 ton stones? There are tensile limits...
So, each rope only needs to be too strong for the individual worker to snap. Obviously, that's pretty easy, even with the worst natural fiber cordage - fibers are strong. Then they meet in some way, and ultimately attach to the wooden sled. The exact math for that is not straightforward, and we don't really know how they tied it off, but it's not an unusual amount of load for a large wooden structure. Assuming the sled measured 100 meters^2^ (80 tons was a special block worthy of an oversize sled), that works out to less than a ton per square meter, and a tree with 1m^2^ cross section at the trunk can weigh several tons without even considering the wind load on the foliage, which will be larger yet for most species.
80 tons is a lot, but it's not a lot a lot. Thousands of tons are pretty common if you're talking about ships, for example. Even the wooden ones; honestly wood is an underrated material.
I don't know any specifics, but a bunch of ropes divides the force on each one. A bunch of ropes, plus people pushing from behind, would probably be enough force to overcome static friction without exceeding tensile limits on any one rope.
Yeah people really forget how recent an invention good rope is, It's not like they could just order a few hundred meters on ebay. Making all that rope would probably be more effort and expense than a lot of the stuff that people write of as too complex for them to have considered, like temporary canals or raise and drop sledding.
Rope braiding is pretty fast. Especially if you're an ancient Egyptian woman who's done it full time for decades. They had hemp, which is the same stuff that rigged up the giant sailing ships of later on in history.