Muon Scanning Finds Hidden Chamber in Great Pyramid of Giza

Gif showing a cross-section rendering of Khufu’s Pyramid in Giza, Egypt showing a "void" that scientists have discovered. The image is labelled to include the Grand Gallery and shows two potential positions of the "void".
Images: Scan Pyramids
This rendering of the Great Pyramid of Giza shows two potential positions of a "void" or chamber that scientists have discovered.

Egypt’s pyramids endured centuries of grave robbing after their construction. More recently, they’ve been poured over and poked at by archaeologists. After thousands of years, it’s hard to imagine they have anything left to hide.

Yet a team of researchers recently uncovered a previously unknown chamber in the Great Pyramid of Giza. What’s more, they did it with a little help from outer space.

Strangely, the chamber isn’t connected with the rest of the Great Pyramid’s internal rooms. Despite there being no way to access it, “we are very confident of its existence,” says Mehdi Tayoubi, co-founder of the Heritage Innovation Preservation (HIP) Institute, which is partly behind the scanning effort.

Not much is known conclusively about the construction of the Great Pyramid of Giza. Built for the Pharaoh Khufu in the 4th Dynasty, very few records exist from the time of the Great Pyramid’s construction roughly 4,500 years ago. Those that do exist don’t describe the construction itself. The first complete description of the pyramid’s construction comes from more than 2,000 years later—not exactly the most reliable source.

So a team of researchers began the ScanPyramids Project, coordinated by Cairo University and the HIP Institute in Paris, and turned to a more consistent source of information: high-energy cosmic rays from beyond our solar system.

It’s still not clear where cosmic rays originate—some come from our own Sun, while the popular theory is that the most energetic rays come from distant supernovae. What is known is that when one hits Earth’s atmosphere, it cascades into a shower of subatomic particles.

One of those particles is the muon. The little particles rarely interact with other matter. Enough of them do, however, that whizzing through solid rock stops more of them than whizzing through the atmosphere.

Which is why the team used muons to scan the interior of the Great Pyramid. By placing detectors on the floor of the Queen’s chamber, which is the lowest chamber inside the pyramid, as well as outside, the team could detect muons coming through the pyramid. The idea was, if there are more muons hitting the detector from a direction than would be expected, they’re likely passing through a previously unknown empty space.

They found one such space, higher up in the pyramid. They detailed their findings in a paper published today in Nature.

If the empty space is actually a chamber, it would be the first major chamber discovered since the 19th century. To date, archaeologists only know about three major chambers inside the pyramid. Besides the Queen’s chamber, there is the King’s chamber, located higher up, and the Grand Gallery that connects the King’s chamber to the entrance tunnel.

Probing pyramids with muons isn’t a new idea. In the late 1960s, a team led by Nobel-winning physicist Luis Alvarez used muon detectors [pdf] to scan for undiscovered rooms in the Pyramid of Khafre, the Great Pyramid’s slightly smaller neighbor. They found nothing but solid rock surrounding previously known rooms.

ScanPyramid’s efforts on the larger pyramid appear more fruitful. They used three distinct muon scanning techniques. Two were in the Queen’s chamber to watch for muons from above, and the third, a larger detector, was placed along one side of the pyramid, to catch muons after they’d passed through the structure at an angle. The results of all three agreed: There’s a large space directly above the Grand Gallery, something the researchers now call the Big Void.

Not everyone agrees with the ScanPyramids team’s interpretation. Zahi Hawass is the former Minister of Antiquities for the Egyptian government and chaired a committee that reviewed the results. “I do believe we have to be careful about the word ‘void,’” he says.

He says the researchers arrived at the wrong conclusion because they don’t understand the construction of the pyramid. According to Hawass, the Great Pyramid is full of smaller voids between the large stones, to reduce the overall weight and stress of the structure. What the ScanPyramids team interpreted as a single undiscovered chamber, he says, is actually nothing more than the regular interior structure of the Great Pyramid.

Hawass, who has been the public face of Egyptian archaeology for years and has had a tumultuous history with non-Egyptian researchers, says the research team cannot even definitively state the size, shape, or position of the chamber. He accuses them being in it for the publicity. “The search should be scientific,” he says, “not a search for attention.”

The ScanPyramids team acknowledges the imprecision in their results, admitting that the chamber’s apparent location directly above the Grand Gallery made it difficult to determine its dimensions. “It is there. What is it? We do not know,” says Tayoubi of the HIP Institute. At this point, the team won’t hazard an interpretation, but remains confident in their data.

Others agree with their conclusion. “I am very confident that they did a good job, that it’s a reliable result,” says Konstantin Borozdin, vice president of physics and analytics at Decision Sciences. Decision Sciences has helped develop a system for muon scanning, though with a different technique, at the Fukushima Daiichi nuclear power plant in the years following the 2011 disaster.

Borozdin says the main strength of the data is the fact that all three methods independently turned up a similar signal. That means it’s much more likely that the ScanPyramids team actually detected something instead of just noise.

While he believes the results are valid, he also cautions patience. He thinks the data is clear enough to distinguish between the Big Void and gaps in the structure, but says the ScanPyramids team should continue scanning from as many angles as possible to build a more complete three-dimensional image.

For their part, the ScanPyramids team is content to continue scanning. At the moment, attempting to access the chamber is off the table. Hawass says he intends to refute their conclusions in his own paper, while the team plans to continue non-destructive measures of scanning the pyramid. The ScanPyramids team says they’ll only consider finding a way to enter the chamber when all scientists agree on their results.

Editor’s note: This story was updated on 3 November to clarify the role of Decision Sciences in muon scanning at the Fukushima Daiichi nuclear power plant.

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