Thread by @Andercot

Extraordinary Claims Require Extraordinary Evidence.

A news story broke there's massive structures beneath the Pyramid of Khafre, something far beyond the tech level assumed of ancient Egyptians.

What can back these claims? Extraordinary technology: Synthetic Aperture Radar🧵

First lets start with optics - in general a larger lens lets your resolve finer and finer details.

Roughly, the angular resolution goes like wavelength/diameter.

This makes sense if you think about how waves are diffracted - smaller waves or larger opening, less diffraction

But optics just uses a range of radio frequency spectrum we call visible light. The exact same physics applies for radar systems.

But radar uses far far larger wavelengths, on the scale of meters versus nanometers for visible light. What can we do?

Make the aperture massive

Synthetic Aperture Radar does exactly this by forming an 'imaginary' lens by sweeping the radar system across the sky, taking a succession of radar snapshots that are then reconstructed into a single image.

The mathematical framework for this was developed first in the 1950s and applied to airplanes through the 1950s - 1960s. At the time these tested the limits of both radar power and computational image processing.

These days the SAR market is exploding - thanks to decreasing launch costs, higher performance computing, solid-state RF amplifiers, the resolution for SAR systems in orbit.

Now enter @capellaspace and the Pyramids of Giza

These systems provide the best commercial SAR resolution in the world, well actually, in space. @capellaspace latest platform upgrades bring the azimuthal resolution down to 5cm

But, radar can't penetrate pyramids. How do you image the inside to find hidden structures?

This is where it gets insanely cool. SAR doesn't just give pixel-by-pixel angular resolution, but by looking at each component of frequency they can also find the doppler shift from each pixel.

Doppler shift comes from the movement of the imaging surface relative to the wave

The exterior surface of the Pyramid is slightly vibrating from seismic tremors in the Earth and atmosphere, and exactly how it shakes reveals information about its interior structure.

There is a lot of math I'm skipping here but - you can reconstruct interior features

The feature reconstruction is extremely impressive - you can make out individual roof segments in the King's chamber

By performing this process all over the exterior sides you can start reconstructing interior passageways, vaults, hidden chambers, things completely buried and otherwise unobservable

In the original publication the authors reach a fairly profound conclusion - that the Pyramid of Khafre acted as a giant hydro-acoustic device designed to produce very specific and concentrated fields of acoustic resonance in the Kings and Queens chamber

This more recent press release is from subsequent work by the same team - finding now that there are massive cylindrical wells beneath the pyramid claimed to extend 600 meters below the surface.

This is totally beyond anything conceived of as 'engineering ability' at the time

Any indication of this from other sources? Incredibly, yes.

Herodotus claimed that in the construction of the Pyramids, 10 years were spent on the passageways and caverns beneath the Giza plateau, while 20 years spent on the Pyramid itself.

The SAR team also claims, like Herodotus, that there are passageways underground extending across 2km of distance underneath the Giza Plateau.

This is all utterly insane and cool so I'll just say this:

Civilizations is likely way older than we think