440 Royal Cubits (20.632 inches per Cubit) per base side of the Great Pyramid of Giza, 280 for the height, so two base sides, 880, divided by 280, equals Pi, and the base perimeter length of the Great Pyramid is half a nautical mile, so it's a reduction of the dimensions fo the Earth by a factor of 43,200, derived from the rate of precession, 72 years per 1 degree of 360 degrees.
The ancients measured the radius of the Earth, according to the rate of precession, by measuring one side of a hexagon which is circumscribed by the circle of the Earth, and subdivided this length by 7,200 for the base perimeter length of the Great Pyramid, and therefrom, the length of the royal cubit.
The pyramids aren't even that perfect. The first few pyramids built were failures. (the first pharaoh to build large pyramids built three in his lifetime). One was abandoned when the foundations started to shift, the next one had to be changed when the grand-chamber started cracking. This is the pyramid with the change in slope 2/3rds of the way up. They did this to reduce the mass above the chamber. (this was before they figured out how to arch with corbels)
I've seen studies of the use of phi in pyramids that were debunked when new measurements were taken of the pyramids and found out that the original numbers were fudged. A lot of this nonsense math comes from false beginnings.
The best way to debunk this crap is to study ancient Egypt. There is no mystery regarding the pyramids. Before the Old Kingdom, there was an Archaeic period where kings were build under large stone structures. All Egyptians tried to bury themselves under stone, because the sand would shift and expose bodies, and there was the threat of high Nile floods. These large stone structures got bigger and bigger, and the only way to make things really large, and be structurally stable, is with a pyramid. That's why the same shape has been discovered by dozens of different cultures. It has to do with properties of the shape, NOT with anything going on with the cultures. Dump a bucket of sand on the ground slowly to see this for yourself.
The reason the pyramids were only built during the Old Kingdom was because those graves were robbed and decimated during the first intermediate period. Middle Kingdom pharaohs realized that these pyramids were a TAD obvious, and the Valley of the Kings was born. (not that these fared any better during the second intermediary period. Only a few were not found and robbed)
The true story of the pyramids is better than any of the bullshit alien conspiracy theories. Too bad the pseudo-intellectual waste their time on fiction, when reality is far more fascinating.