> Hounsfield pondered whether it was possible to detect hidden areas in Egyptian pyramids by capturing cosmic rays that passed through unseen voids.
I also wondered about this possibility a few years ago and when I searched online, I found an example of muon tomography of the volcanic dome of La Soufrière on the island of Guadeloupe[1]. Cool non-seismic approach to a difficult imaging problem.
Specifically, I was wondering about neutrino tomography of the entire earth, but the low probability of neutrino collisions would seem to make that infeasible.