Cosmic-Ray Muons Reveal Hidden Void in the Great Pyramid

A void as tall as the Statue of Liberty has been detected in Khufu’s pyramid, otherwise known as the Great Pyramid, using a technique of modern particle physics.

While it is presently unclear what function the large void played back in Ancient Egyptian times, experts are hoping that this gaping hole in Giza’s most imposing pyramid could help answer some persistent questions archaeologists and historians have about its construction. There is still no consensus as to how the Great Pyramid was built.

An aerial view of Khufu’s pyramid

“We have been very surprised to discover something so big—a big anomaly,” said Mehdi Tayoubi, one of the authors of the paper, during a press conference Wednesday. The team published its findings in the journal Nature today.

Tayoubi, Kunihiro Morishima, and their colleagues imaged the pyramid using muons, which are by-products of cosmic rays that form in the Earth’s upper atmosphere and can penetrate stone. Muons have distinct trajectories when moving through air as opposed to stone; an area with lower-than-expected density will see a higher-than-expected flux of muons.

In this way, scientists can use muon detection technologies to differentiate cavities from solid structures.

Tayoubi pointed out that, if the team can deploy the muon detector for a longer period of time, “we can get a more precise, penetrating image of the pyramid.” Muon detector technologies have already been used in particle accelerators, for volcanic research, in Fukushima’s nuclear reactor, and for homeland security.

The engineers involved in the research, called the Scan Pyramids project, are most interested in the fact that the void has a cross-section similar to the well-known Grand Gallery, which is lies below it. They also suspect that this new discovery could lead to clues about the pyramid’s construction. “A new void will help [our] understanding of the sequence of the construction of the pyramids,” said another of the paper’s co-authors, Haney Helal. “However, having said that, we should be very cautious at this time of going too far beyond the observation of the void.”

In the future, the team is thinking about acquiring artificial intelligence to send a malleable robot through small holes to explore the insides of these structures. “This mission is understanding the pyramids,” Tayoubi said. “But above all, it’s about innovation.”

Explore Ancient Egypt’s pyramids in 360˚ detail in our interactive feature.