Discovery of New Spaces in Khufu's Pyramid via Cosmic-Ray Muon Imaging

Exploiting the high penetrating power of cosmic-ray muons, we have been developing "cosmic-ray muon imaging", which visualizes the integrated density distribution inside objects up to several kilometers thick. Since launching the ScanPyramids project in 2015, we have used this technique to probe unknown interior structures of the Great Pyramid of Khufu in Egypt. In 2016 we discovered a passage-like space behind the northern face; in 2017 we found a massive void at the center of the pyramid. Subsequent muon-imaging observations refined the position and shape of the passage-like space, and in 2023 we first succeeded in photographing it with a fiber endoscope — observing its 4,500-year-old interior for the first time. This talk describes the muon-imaging method and how these spaces were discovered, and presents future prospects.