Inside the Great Pyramid of Giza, tourists were only one complication for Mehdi Tayoubi, the president of the Heritage Innovation Preservation. The feeling side the pyramid is one of having “a massive amount of stone above you and around you.” The humid, cramped conditions of the pyramid’s tunnels and chambers can be unnerving—a don’t even think about getting a phone signal.
Mehdi was expecting all of those things. What he was not expecting was to find an anomaly in the data provided by their particle-scanning machines.
“We knew at this time we had something big but said we have to take our time,” he says. Now, a few years later, the team has announced the discovery of a previously unknown void inside the 4,000-plus-year-old pyramid. It is the first major inner structure found inside the Great Pyramid since the 19th century.
“It could be comparable to the Grand Gallery,” Tayoubi said, describing a space 30 meters long and 21m above ground level. The space was discovered above the Grand Gallery inside the Pyramid of Khufu. The Grand Gallery is a 8.6m high, 46m long passage connecting some of the key areas of the pyramid.
“We cannot say at this moment if it is a second grand gallery, if it is a big tunnel, if it is a successive chamber, or whether it is horizontal or inclined,” Tayoubi says. “We don’t know what it is.”
To map the void researchers used particle physics detectors, which produce muons.
According to Wired:
One by-product of cosmic rays is muons. “They’re a fundamental particle in the sense they’re one of the indivisible building blocks of matter,” Lee Thompson, a professor of experimental particle physics at the University of Sheffield says. Every minute, he says, a muon will pass through a surface area the size of a person’s thumb. “We’re sort of bathed in them all the time”.
The Nature paper detailing the void describes how muons are absorbed by the pyramid’s stone structure and a lack of detected muons in the area of the void reveals its existence. “If we pointed a detector in a certain direction we would know what we would expect to see,” says Thompson, who wasn’t involved in the research but was involved in the peer review process says. “They looked for differences in what they expect to see and what they do see.”
Away from using muon detectors inside the pyramids, the technique has been widely used to inspect the insides of hard-to-reach objects. Muons have been used to study the structures inside Mount Vesuvius and to inspect the cargo for illicit nuclear material smuggling. “It’s a nice fusion of particle physics and archeology,” Thompson says of the pyramid work. “That’s something you don’t say very often.”