[MarcusBrutus]

I am not convinced that the Egyptians could build watertight channels at this scale, especially those shown climbing up the slope of the pyramid which would have to be watertight at the top too, and under great pressure. Also one or two packages could easily get stuck in the "pipe" jamming the whole thing. Finally, the video likely downplays the number of floaters necessary to lift a block of stone.

[FrankenPC]

Yes. I thought the same exact thing. Also, I was wondering exactly how the water was magically moved around a the top of the pyramid? I can see evacuating sections, but then you would have to wait for the next rains to refill them. That would take an incredibly long time. Imagine how much work would be required to bring more water to the top of that pyramid to refill the sections AND the leaking flotation columns. Heck, imagine the PSI of water at the bottom of the pyramid columns when they were reaching a hundred feet high?

[schiffern]

>That would take an incredibly long time.

Note that Egypt was a lot wetter when the pyramids were built (circa 2500 BCE). http://www.pbs.org/wgbh/nova/next/ancient/climate-change-may...

>Heck, imagine the PSI of water at the bottom of the pyramid columns when they were reaching a hundred feet high?

A column of water 100 feet high exerts 43 psi at its base.

[FrankenPC]

OK. So, the great pyramids were nearly 500ft tall. At the top, the pressure below would have been around 200psi. Even the most stalwart modern plumbing fixtures have trouble past 72psi. 100psi is the upper limit before things start to fail. I don't think that there would be a mechanical problem with stone holding back that pressure, it's the leakage that would be the killer.

[maxerickson]

Modern plumbing stuff is designed to be economical. (Which just limits the usefulness of extrapolating from there)

If the mechanics of using the stonework to hold the water were well worked out I would think clay would work well to seal small cracks (and for the scale we are talking about, the 'plumber' could just crawl on in). Or pitch or other sticky stuff.

[mekoka]

The theory mentions multiple shafts, not a single contiguous one.

[allochthon]

How feasible is it to even float massive stone blocks by attaching animal skin balloons to them as is done in the video? I would have figured that you would need many more than are shown. Also, how would you protect the balloons from pushing out of their restraints as they rub against the upper diagonal wall of the near-vertical channels?

[FrankenPC]

(I have no idea what I'm doing...) how much does 1 cu-foot of water weigh compared to 1 cu-foot of limestone? water is about 63Lbs / cu-foot. limestone is 163 Lb / cu-foot. So, 1cuf stone in water is 163-63=100Lb (it's already partially buoyant because it's IN water). Then you need to evacuate water using air bags that are ABOUT 1.5 times the blocks size. So, the whole payload would be 1 unit block with 1.5 units of air. or 2.5 units total. Much bigger than the video suggested. But not unreasonable.

[bradleyland]

It's much easier if you work in metric units (as usual).

The density of water is 1,000 kg/m³.

The density limestone is around 2,500 kg/m³ (it can actually go down to around 2,100 kb/m³).

This means that you'd need to displace more than 2 to 2.5 times the volume of water in order to float a limestone block. Keep in mind that volume goes up (roughly) as a cube of the increase in linear dimension, so the difference won't be quite as dramatic as it first seems, but that's still a lot of flotation required. Certainly much larger than the floats shown in the video.

The animal-skin bladder theory is particularly problematic, because the volumetric efficiency of spheroid animal-skin bladder floats isn't particularly good. Water would fill in the space between bladders, requiring much larger float assemblies than if they were able to construct larger, single-chamber bladders. The video depicts float assemblies that aren't even as large as the blocks they were transporting. I found that rather disappointing for an engineering-driven theory.

[FrankenPC]

Yeah. So, the "hats" of bladders on the block can't be too high because the depth of water would be impossible to maintain. Therefore, they would have to be wide. That would limit the number of floating blocks you could have at any given time. It would also present a problem with the gravity conveyor to the top of the pyramid.

[mekoka]

As it certainly doesn't need to be proven further, Egyptians were quite an ingenious people. All of the things you're suggesting as obstacles would probably be trivial to deal with for them at their advancement level. A commenter (seferphier) posted this link that may provide a glimpse into additional possible cues, I suggest to have a look http://www.youtube.com/watch?v=C1y8N0ePuF8&feature=youtu.be&.... I particularly liked the part where it is suggested that it would be relatively easy for them to move 600 litres of water in a single minute. With virtually unlimited water and such a capacity to move it, I think the theory might be plausible and merits further investigation.

[maxerickson]

Density of limestone is about 2.5, so the volume of floats would be about 2.5 times the blocks.

[yason]

I'm tired but isn't that just 1.5 times?

Tied together, a 1m³ block of limestone and a volume of 1.5m³ of floats displace 2.5m³ of water. Assuming the mass of the floats themselves isn't much then already that would lift 2.5 tons off from the bottom of the water pool.

[maxerickson]

Yeah, I got it wrong.

[MarcusBrutus]

Shouldn't that be 1.5X instead? Unless you are factoring in that limestone's permeable.

[mekoka]

Are you taking into account the surrounding water (density=1) in your calculations?