https://www.youtube.com/watch?v=YTgxGJfXRQ0 The premise of Jean-Pierre Houdin is that there are undiscovered internal tunnels in the Great Pyramid (and presumptively the other larger pyramids) that were used for the construction. If nothing else, these are interesting computer animations of his theory. It remains unproven. Surprisingly, nothing is said about the neighboring Kahfre pyramid, which is nearly the same size and would have required similar construction. We should know in a few years whether there is merit to his suggestion.
I forget who did it (some well know scientists) did set up some cosmic ray direction sensitive detectors (I think from memory) in the one or more of the known internal chambers, but after many months of data collection and analysis concluded there were no more, yet to be discovered, chambers of significant size. If there were a long tunnel in it probably their tests would probably have shown it but possibly not if it is a long conical construction ramp for dragging blocks up inside.
that was Louis Walter Alvarez, who worked with cosmic rays in the pyramid. http://www.gizapyramid.com/hidden2.htm ; not to be confused with Walter Louis W. who worked with cosmic rays at Berkeley when L.W. Alvarez was still around (not to be confused with Alvarez' son, W.L. Alvarez, who proposed the meteroritic demise of dinosaurs). But later others set up 'microgravimetry' results that seemed to produce a perplexing result of voids in a spiral pattern. They didn't publish it, but later when Houdin was voicing his theory, they contacted him with their results, and the two mesh. Not proof, but quite intriguing.
