berkeman said:
I wonder why there aren't a bunch of Egyptian drawings of the big stones on boats. You would think they would have been proud to document their clever pyramid building techniques...
The rocks could be supported, suspended underwater, under a raft. That is not visible from the surface. By moving the rocks underwater, the boat/raft buoyancy required is significantly reduced, while the vessel changes from being unstable to being unconditionally stable. The fact that there are no pictures of rocks on the top of boats, demonstrates ancient Egyptian intelligence.
Buoyancy is proportional to volume, so the advantage of suspending the rocks underwater is greatest for the lower-density limestones employed in the construction. The more dense granite, with a density of about 2.7, weighs 2.7 tonne per cubic metre, dry, in air on a boat. Underwater, 1m
3 provides one tonne of buoyancy, so only needs 1.7 tonnes of additional buoyancy from the raft or boat to provide support.
Rock drilling produces chips that float in high density bentonite drilling mud. A rock can be moved by dragging it, submerged, through the mud on the bottom of a canal, or floated with neutral buoyancy, along a mud filled canal. That would require canals connecting still backwaters, so the lubricant mud was not flushed away by floods, to be replaced by abrasive sand at times of high river flow. The majority of the clay from such a transport system would not remain today, as the fluid mud would be lost during a 1000 year flood.
Bandersnatch said:
Could ancient humans with their primitive technology move the longest river on Earth like that? And if not, who helped them?
Rivers move naturally in their valley. Rivers meander and move as sediment is eroded from the outside of the bends, being deposited on the inside of the next bend.
There are many straight canals running parallel with the Nile in the valley. They follow the ancient river channels and oxbow lakes. Many have been maintained for transport and irrigation for thousands of years.
