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Still Waters

Why Egypt Stopped Building Pyramids

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When structural engineer Peter James arrived at the Bent Pyramid, 25 miles south* of Cairo, his task was to secure the structure's remaining "cladding" -- its smooth exterior envelope. But why was it crumbling in the first place?

The foundation seemed completely stable. The prevailing theory -- that "the missing cladding was removed by local opportunist thieves" -- didn't inspire confidence: That could explain the destruction at the lower levels, but the damage extended far up the pyramid and "in an apparently random manner, with no signs of indentations from temporary scaffolding or of any symmetrical cutting of the blocks to aid removal,"

http://www.theatlant...yramids/275738/

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cute theory if we ignore that half the old town of Cairo is built out of Pyramid cladding. The reason for the lower levels of the cladding still being there is because most were ignorant of its existence until they started digging around the pyramids.

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I assumed they stopped due to financial issues - maybe they elected progressives once too often :w00t: :tu:

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According to Geordie folk tales,they stopped because they ran out of straw,and without straw they couldn't make bricks,so Joshua (he was the Foreman and always wore Wellies)went to see the Pharie to explain,but the Pharie wasn't amused and decided to hoy them oot of Egypt.......and the tale goes on and on.

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Aye ... a pint of your darkest ale for spud the macken .... a barrel if your back is up to it ... we'll send the bill to the Pharie ...

:tu:

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I always thought they stop building them because of economic conditions.

Spud is such a party animal.

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Posted (edited)

i sort of guessed it might have been mainly due to a change in beliefs ¿ His "thermal fluctuation" idea causing movement of the blocks was interesting . I always wondered about earth tremors causing some of the damage.. but, alas , apparently there are no geologic faults in that area?

* No more beer for Spud, for awhile, He'll be telling us they were built by the wee folk.. until they ran out of beer.

Edited by lightly
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The idea that the stones were moved by thermal expansion and contraction is actually a good idea, but I wonder then why so much of the cladding remains? Was part of the Bent Pyramid in the shade? Did the base and corners get more sun then the flat sides? Probably this is Part of the answer, but even Mr James has to rely on the locals coming by and dragging off the stones that fell off. Deconstructing the Pyramid cladding still seems very likely to me.

Does the amount of cladding on each of the pyramids correlate with how far it is from an ancient town/city? Seems like it does to an extent.

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one would think the aliens would have taught them better. after traveling gazillions of light years to get here and showing the primitive ape beings how to make timeless monuments for them and then have this happen. It is no wonder they haven't tried to contact us since they are either mad or ashamed.

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The answer is simply that the labourers went off to the promised land,so they couldnt continue without a work force,and they were too bloody lazy to carry on themselves.

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The idea that the stones were moved by thermal expansion and contraction is actually a good idea, but I wonder then why so much of the cladding remains? Was part of the Bent Pyramid in the shade? Did the base and corners get more sun then the flat sides?

The original article in Structure explains why the thermal expansion would have made more destruction on the angles and at the basis: "The distress at all of the perimeter edges suggests that the outer casing has expanded from the center outwards, and movement has taken place on all of the extremities.
"

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The original article in Structure explains why the thermal expansion would have made more destruction on the angles and at the basis: "The distress at all of the perimeter edges suggests that the outer casing has expanded from the center outwards, and movement has taken place on all of the extremities.
"

The problem there is that this would not have been unique to the casing but applicable to all stone structures in the area. Except for the casing it all seems to be there (or at least what centuries of mining stone for Cairo from the pyramids has left).

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The problem there is that this would not have been unique to the casing but applicable to all stone structures in the area.

Maybe it's more relevant for the casing than for the rest 1° because the casing was so precisely set, so that there is no place for any expansion between the blocks; and 2° because the other structures rarely have limestone walls 230 meters long :)

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Maybe it's more relevant for the casing than for the rest 1° because the casing was so precisely set, so that there is no place for any expansion between the blocks; and 2° because the other structures rarely have limestone walls 230 meters long :)

with 8m/K, given a maximum temperature variation of maximum 10 Celsius (Giza average) it seems to me that this is surely a case of "back to the drawing board", especially given that once the stones moves its maximum distance it will shrink again leaving a gap causing no future work until the maximum is surpassed again.

Nice try, but no dice. BTW, there are many stone buildings in the world where there are greater temperature variations and are longer without having crumbled due to temperature differences over the last 2000 years (just look at the Roman aqueducts).

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with 8m/K, given a maximum temperature variation of maximum 10 Celsius (Giza average)

But you can't take an average temperature maximum and minimum, you have to look at the difference between the daily maximum and minimum on the casing stones, the diurnal temperature range. I don't know what it is in Giza, but it can easily be more than 30°C in the desert, moreover near the surface. According to the original article:

During the day, the temperature rises to 40°C (104°F) across the face of the outer casing, then at night cools to 3⁰C (37⁰F) because of the lack of cover and exposure to the prevailing winds. This gives an average daily temperature fluctuation of 37°C (67°F).

It's probably a little overestimated, but I think that your "maximum 10 Celsius" is underestimated :)

it seems to me that this is surely a case of "back to the drawing board", especially given that once the stones moves its maximum distance it will shrink again leaving a gap causing no future work until the maximum is surpassed again.

Again according the original article:

All movement from the thermal expansion of the casing would be taken up initially in the joints, but would also cause dust and stone particles to detach from the stones, filling the voids and gaps between them. This would reduce the amount of contraction possible at night, along with the stones’ natural propensity not to return to their original dimensions and position
Nice try, but no dice. BTW, there are many stone buildings in the world where there are greater temperature variations and are longer without having crumbled due to temperature differences over the last 2000 years (just look at the Roman aqueducts).

There is a difference between "crumbling" an entire construction, and dislodging a few blocks at the angle of the same construction. The phenomenon of thermal expansion dislodging blocks in a natural wall has been documented by the geomorphologists, for instance here.

Please note that I do not think that all the casing stones fell from thermal expansion. But this mechanism, in my opinion, fits quite well particularly with the Bent Pyramid, where it would at least partly explain why the casing has disappeared on the angles and not in the center of the faces.

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But you can't take an average temperature maximum and minimum, you have to look at the difference between the daily maximum and minimum on the casing stones, the diurnal temperature range. I don't know what it is in Giza, but it can easily be more than 30°C in the desert, moreover near the surface. According to the original article:

It's probably a little overestimated, but I think that your "maximum 10 Celsius" is underestimated :)

Again according the original article:

There is a difference between "crumbling" an entire construction, and dislodging a few blocks at the angle of the same construction. The phenomenon of thermal expansion dislodging blocks in a natural wall has been documented by the geomorphologists, for instance here.

Please note that I do not think that all the casing stones fell from thermal expansion. But this mechanism, in my opinion, fits quite well particularly with the Bent Pyramid, where it would at least partly explain why the casing has disappeared on the angles and not in the center of the faces.

The maximum/minimum average in Giza never surpasses the 10 degree mark (according to the Egyptian meteorological office), that is the point ignored here and with those 10 degrees the maximum expansion of a whole row of casing stones could not have been more than a few tenths of a millimeter, that and given the fact that the casing stones did not rest on each other but on the block ledges being held with mortar against the rough side of the construction already makes the whole theory have a gap a whole herd of elephants can run through.

The other hole is, as I mentioned, as soon as they have the gap (again, of a few micrometers) they stop working against each other, which is the other part ignored in that theory.

And yes, Giza surpasses 30 degrees, but those conditions also existed when the pyramids were built so the likelihood is that the expansion gaps were already there before the construction was ever finished. If the casing stones would have been as long as the pyramid itself I could see the merit to this, but given that they were relatively small and set in a gypsum bed (which means that they would have had gaps already very early on because the gypsum would be the first to go under the expansion pressure) plus that the casing was angled inwards (as we can easily measure from the still existing) of the face and not straight, this whole scenario is less likely.

Last not least, we have historical reports of people "mining the pyramids" for building materials in the last 7-8 centuries.

The only possibility I see is that temperatures suddenly tripled or quadrupled from the previous night temperature. But from the records we have that is very little likely. And it would mean that on some given day there would have been a maximum temperature of over 80 C (Celsius, in Fahrenheit that would be around 180) that lasted long enough to heat up the blocks to the same temperature. If that happened we would surely know about it because it would be recorded as the day all inhabitants on Cairo died.

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Again according the original article:

All movement from the thermal expansion of the casing would be taken up initialy in the joints, but would also cause dust and stone particles to detach from the stones, filling the voids and gaps between them. This would reduce the amount of contraction possible at night, along with the stones’ natural propensity not to return to their original dimensions and position

I would seem to me then that to topple a stone such as the cladding on the Great Pyramid, that a tremendous amount of sand would be needed. The cladding stones are like 10 tons, so figure probably 2 or more tons of sand would need to get behind each block to push it out far enough to topple.

I'm not sure how big the cladding stones on the Bent Pyramid are, but still it would seem if this (thermal expansion) was a major factor that most, if not all, of the cladding stones would have significant amounts of sand behind them. And, I don't believe that to currently be true. The thermal expansion should affect all the stones, and the dust and sand should be equally available across the pyramid, IMHO.

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Posted (edited)

Just to clarify why I think, without endorsing the author's ideas about the end of the pyramids building, that his idea of thermal expansion is interesting in the case of the Bent Pyramid:

BentPyramid.jpg

While there is no problem with the idea of people mining the pyramid along the basis, and going up along the angles where the blocks were surely easier to dislodge, I find rather strange the place within the red circle: why would scavengers take the blocks off going up along the angle, then stop, go to the top of the pyramid, and then take off the blocks going down along the same angle from the top? There could be a practical explanation that I don't see presently; but the thermal expansion idea has the advantage of explaining the highest degree of destruction along the angles during the thousands of years of weathering.

Edited by Irna
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with 8m/K, given a maximum temperature variation of maximum 10 Celsius (Giza average) it seems to me that this is surely a case of "back to the drawing board", especially given that once the stones moves its maximum distance it will shrink again leaving a gap causing no future work until the maximum is surpassed again.

Nice try, but no dice. BTW, there are many stone buildings in the world where there are greater temperature variations and are longer without having crumbled due to temperature differences over the last 2000 years (just look at the Roman aqueducts).

Consider also the temperature of the stone when it was fitted in place.

If it was winter, there might be a problem. If summer, then no troubles.

Harte

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