Engineer: Egyptians built pyramids by piling rubble and attaching bricks later • Hacker News Board

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#21

Post by FrankenPC » Sun, Jan 12, 2014, 6:04 PM UTC

MarcusBrutus wrote: post #16

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.

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?

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#22

Post by maxerickson » Sun, Jan 12, 2014, 6:04 PM UTC

MarcusBrutus wrote: post #16

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.

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

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#23

Post by pepijndevos » Sun, Jan 12, 2014, 6:05 PM UTC

My favorite theory is that the blocks where cast in place.

The part where they float the blocks up the side seems dubious to me.

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#24

Post by FrankenPC » Sun, Jan 12, 2014, 6:11 PM UTC

allochthon wrote: post #20

MarcusBrutus wrote: post #16

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.

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?

(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.

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#25

Post by MarcusBrutus » Sun, Jan 12, 2014, 6:15 PM UTC

maxerickson wrote: post #22

MarcusBrutus wrote: post #16

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.

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

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

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#26

Post by yason » Sun, Jan 12, 2014, 6:17 PM UTC

maxerickson wrote: post #22

MarcusBrutus wrote: post #16

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.

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

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.

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#27

Post by maxerickson » Sun, Jan 12, 2014, 6:18 PM UTC

yason wrote: post #26

maxerickson wrote: post #22

Earlier quoted context omitted.

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

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.

Yeah, I got it wrong.

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#28

Post by andyidsinga » Sun, Jan 12, 2014, 6:18 PM UTC

i love this - even if it turns out to be not fully correct in the end. one thing i was wondering was if any evidence had been found about about the balloon floatation devices, and, along similar lines, if they modeled the idea that small barges atop the blocks might have worked instead of balloons.

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#29

Post by mekoka » Sun, Jan 12, 2014, 6:20 PM UTC

maxerickson wrote: post #22

MarcusBrutus wrote: post #16

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.

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

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

Re: Engineer: Egyptians built pyramids by piling rubble and attaching bricks later

#30

Post by FrankenPC » Sun, Jan 12, 2014, 6:31 PM UTC

OK. How about if they also built a large water tower on top of the pyramid? The seasonal rains would be trapped in the basin(s) and used to refill channels and replace water lost due to leakage?