A hidden internal structure in Khufu’s Pyramid, the largest pyramid in Giza, Egypt, is uncovered in research published in Nature this week. The discovery was made using cosmic-ray based imaging, demonstrating how modern particle physics can reveal new information about ancient structures.

The Great Pyramid, or Khufu’s Pyramid, was built during the reign of Pharaoh Khufu (Cheops), who reigned from 2509 to 2483 BC. There is no consensus on how the monument was constructed. To learn more about the internal structure, Mehdi Tayoubi, Kunihiro Morishima and colleagues imaged the pyramid using muons - by-products of cosmic rays that can penetrate stone. Muons have distinct trajectories when moving through stone or air, making it possible to distinguish cavities from solid formations.

The authors report the visualization of a large void using three different muon detection techniques. They estimate that the void is at least 30 metres long, and has a cross section similar to that of the Grand Gallery, which lies beneath the newly discovered void. The precise structure and role of this void remain unknown, but the findings may pave the way for further studies that could help researchers to understand the pyramid and its construction process.