Muons of Khufu...

Virtual-reality representation of the interior of Khufu's Pyramid. The small structure with the peaked roof near the bottom of the pyramid is the Queen's Chamber where the emulsion and hodoscope detectors were installed. The large inclined structure is the Great Gallery, which leads to King's Chamber. The new void is the white region above the Great Gallery. (Courtesy: ScanPyramids)

Topics: History, Modern Physics, Particle Physics

A large void hidden deep within Khufu's Pyramid at Giza in Egypt has been discovered by a team of physicists. The first-ever image of the mysterious structure was taken using muons that shower down on Earth after being created when cosmic rays collide with the atmosphere.

The measurements were done by the ScanPyramids collaboration that includes researchers from Egypt, Japan and France. The team used three different muon-imaging techniques to study the pyramid, which was built in about 2500 BCE and is also known as the Great Pyramid and the Pyramid of Cheops.

Called muography, the technique is similar to radiography using X-rays. Dense materials such as stone tend to absorb muons, which travel relatively unhindered through the air. If more muons than expected reach a detector within the pyramid, it means that they must have passed through an air-filled void on their way.

To verify the existence of the void, scientists from the KEK particle physics lab in Japan installed hodoscopes at a separate location within the Queen's Chamber. These comprise layers of plastic scintillator, which measure muon trajectories. Outside the pyramid, physicists from France's nuclear research agency CEA monitored the muon flux through the pyramid using micromegas detectors. These were arranged in muon "telescopes", which are also able to measure muon trajectories.

Muons reveal hidden void in Egyptian pyramid, Hamish Johnston, Physics World