The cosmic rays may have just revealed a hidden chamber inside the most famous Egyptian pyramid.

An international team led by Kunihiro Morishima at Nagoya University in Japan used muons (muon), a high-energy particle created by collisions of cosmic rays with our atmosphere, to explore the interior of the Egyptian Great Pyramid without would move a single stone.

Mions can penetrate deep into the stone and are absorbed to varying degrees, depending on the density of the stone they meet. By placing the Mion detectors inside and around the pyramid, the team could see how much material the rays penetrated.

"When there is more matter, fewer muons penetrate the detectors," said Christopher Morris of the Los Alamo National Laboratory, who uses similar techniques to image the internal structure of nuclear reactors. "When there is less matter, more muons will penetrate the detectors."

By observing the values ​​of the muons that have arrived at various places in the pyramid and the angle at which they travel, Morishima and his team can map the cavities inside the ancient structure.

This method of exploration - muon radiography - is perfect for sensitive historical sites because it uses naturally occurring radiation and does not cause any damage to buildings.

The Mysterious Cave

The team mapped 3 known chambers in the pyramid - Underground, Queen and King - along with connecting corridors. He noticed a new large "empty space" above the Great Gallery, which connects the Queen and the King's Chamber. This new "empty space" is about the same volume as the Great Gallery. The team believes that it is another "oversized" tunnel similar in size to the Great Gallery, which is at least 30 meters long.

The team used 3 different muon detectors, starting with the nuclear emulsion foil in the Queen's Chamber. Just as the film in the camera is exposed to light to create a photograph, so this emulsion film reacts with the muons and records their trajectory.

Once their initial survey indicated a possible cavity, they confirmed it by placing a tool that emitted light flashes when in contact with the mions inside the pyramid. Outside of the pyramid, they also used detectors to record mions indirectly - by ionizing gas inside the device with high energy particles. Within a few months of mine tracking, all 3 methods confirmed the cavity in the same position.

"It's wonderful," said Morris, a long exposure time increases the robustness of the results. "What they saw was almost definitive," he said, though it would require drilling and cameras to determine whether the cavity is deliberately built by a chamber or just an empty cavity created by a long forgotten collapse.

The team led by Luis Alvarez tried to use Mion radiography to map the pyramid already in 1970 (article here), but it was not able to record new "blanks" at that time. If the discovery is confirmed, it will be the first newly discovered chamber in the Great Pyramid for over a hundred years.

"I'd like to be there the first time he pushes the camera stick through a drilled hole," Morris admitted. "Not every day we discover a new chamber in the pyramid."