Skyscrapers are mostly empty space inside. The Great Pyramid of Giza weighs about 6 million tons, so we’d be producing about 7000 of them annually. Maybe we could just plop them all in the ocean? ;)

I'd probably mess up the arithmetic, but I wonder how many skyscrapers or Great Pyramids could be packed in a volume of 1 cubic mile. That's how much oil we use per year.[0] (All sources combined are equivalent to about 3 cubic miles of oil.)

It would be nice to find a way to bump that up a couple orders of magnitude without actually pulling that much oil/equivalent out of the ground, since there literally isn't enough there.

[0] https://en.wikipedia.org/wiki/Cubic_mile_of_oil

Start with a Great Pyramid of Giza, or locally sourced substitute following the traditional recipe [1]:

  * 5.5 million tonnes of limestone
  * 8,000 tonnes of granite
  * 500,000 tonnes of mortar

For a simple approximation, we ignore ingredients that are not limestone.

mass of limestone in great pyramid of giza

  = 5.5 * 1e8 kg of limestone

Volume of limestone in one great pyramid of giza, assuming medium-high density limestone at 2500 kg / m^3 [2]

  = 5.5 * 1e8 kg / (2500 kg / m^3)
  = 2.2 * 1e5 m^3

allegedly there are 4.168e+9 m^3 cubic metres per cubic mile. That gives about 19,000 great pyramids of giza per cubic mile.

[1] https://en.wikipedia.org/wiki/Great_Pyramid_of_Giza#Material... [2] http://www.natural-stone.com/limestone.html

edit: when i try to estimate by geometry from the pyramid dimensions, instead of by density, i end up with about 2,000 great pyramids of giza, but that's without trying to understand what the volume of a pyramid actually is, because i am not clever enough to do that.

Intuitively, isn't the volume of a pyramid going to be 1/3 of that of a prism with the same width/length/height?