"When a plane full of tourists flies from LA to Cairo so they can visit the Great Pyramid, that one flight uses as much energy as it took to build the Great Pyramid."
Greer was making a point about peak oil. But if his calculation is correct what this suggests to me is that the ultimate energy power is information. The reason we can't use the giga-calories of a jet plane full of fuel to build another Great Pyramid is that we don't have a efficient way to distribute and organize that energy outside of using human slaves on a many decade time scale. We have to burn it rapidly and in bulk in jet turbines.
Maybe with robots we will be able to trickle small calories into efficient machines that will chisel rocks with hammers and drag them uphill.