Hidden void found inside the Great Pyramid using cosmic rays

Pyramid image
Image: Getty Images

Subatomic particles have been used to detect a hidden void in the middle of the Great Pyramid of Giza, potentially giving us new insight into how these incredible structures were built.

A paper published in Nature this month details the discovery of the 30-meter long space found in the largest and oldest of the pyramids. Also known as Khufu’s Pyramid, it has several other previously explored chambers, but this is the first new internal structure to be found since the 19th century.

A team of particle physicists from Nagoya University found the void as part of a collaborative study with ScanPyramids, an organization seeking to uncover the mysteries surrounding these ancient structures. The method they used to discover the void was muon radiography.

Muons are small, elementary particles that are about the size of an electron, but much heavier. They are formed when high-energy cosmic rays from outside of our Solar System collide with the atoms in our upper atmosphere, breaking apart the atoms into subatomic particles like the muon.

This process occurs so often that if you hold out your hand every second that ticks by another muon passes through it. If you didn’t see it passing through that is not only due to the fact that they are unimaginably small, but also because they are traveling at near the speed of light.

Most subatomic particles that result from these collisions decay well before they reach the Earth. Muons, however, due to their relative mass and incredible speed not only reach Earth but can also penetrate beneath it. It is this feature of muons that make muon radiography possible.

Muon radiography is similar in many ways to the X-ray one might receive at the doctor’s office. With a standard X-ray, energetic radiation is passed through a patient onto a photographic film. The denser parts of the patient (i.e. bones) absorb or deflect much of the radiation, and therefore the film shows an outline of the internal structure. Similarly, muon radiography utilizes the constant shower of muons from our atmosphere to determine the density of various objects.

In this study, the researchers placed nuclear emulsion films, film that is much more sensitive than photographic film, within some of the known chambers of Khufu’s Pyramid. As muons passed through the pyramid areas that were dense with stone absorbed or deflected more of the high-energy particles than areas that were more open. The resulting film revealed the large void hidden within the pyramid.

While it is exciting to think that the space could contain hidden treasures, Egyptologists feel certain that is not the case. They are, however, excited to see what insights this discovery will have about how the pyramids were constructed.

In the wake of this discovery, there are a number of theories floating around as to the purpose of the void (some involving aliens I would imagine). Many suggest that it is to relieve stress in order to maintain the structural integrity of the other chambers in the pyramid. Others think it may have served as a ramp to allow the movement of stones used during its construction. Unfortunately, it is unlikely we will get an answer anytime soon.

The mysteries of the Great Pyramid of Giza have eluded researchers for over 4500 years, with this most recent discovery adding to a long list of unanswered questions. For now, it is enough to appreciate that one of the world’s oldest and most well-studied monument continues to surprise us, this time with the help of particle physicists and the cosmos.

Author: Skylar Knight

Skylar is currently in the MSc Science Communication program at Imperial College London. He has years of experience working in science museums, academic publishing, writing, filmmaking, and science education.