Researchers have discovered a large hidden cavity inside the Great Pyramid of Giza—also known as the Cheops (Khufu) Pyramid—using subatomic particles called muons.
Although the Great Pyramid is one of the oldest and largest monuments ever built, many questions remain about how it was constructed.
Investigating the internal structure of a monument made of roughly 2.3 million stone blocks—each weighing about 2.5 tonnes—is no simple task. For the first time, scientists from Japan, Egypt, and France have applied advanced particle-physics techniques to explore what may lie hidden behind the pyramid’s massive stone walls.
The discovery was made as part of the ScanPyramids project—an international research mission launched in October 2015 under the authority of Egypt’s Ministry of Antiquities. The initiative aims to study Egypt’s largest pyramids non-invasively using multiple scanning technologies.
Deep within the structure—above the so-called King’s Chamber—researchers detected a previously unknown void at least 30 meters long. It is the first major internal structure identified inside the pyramid since the 19th century.
The findings, published in Nature, were made possible using muon imaging. Muons are subatomic particles produced when cosmic rays collide with Earth’s atmosphere. They travel at speeds close to that of light and continuously shower the planet.
Muons are similar to electrons but far more massive, allowing them to penetrate dense materials such as rock. In fact, tens of thousands pass through every human being each minute. They can even be detected kilometers underground in deep mines.
Because muons pass differently through solid stone than through empty space, scientists can track their trajectories to identify hidden cavities within otherwise solid structures—a technique known as muon tomography.
To ensure accuracy, three independent research teams conducted separate experiments using different muon-detection methods. All arrived at the same conclusion: a large void exists above the King’s Chamber, measuring at least 30 meters in length and several meters in width—comparable in scale to the pyramid’s Grand Gallery.
“We know that this big void has the same characteristics as the Grand Gallery. It’s really impressive,”
— Mehdi Tayoubi, HIP Institute, Paris
The purpose of the cavity remains unknown. Researchers worldwide are eager to understand why the space exists and whether it contains artifacts or structural features. It is still unclear whether archaeological exploration or physical entry will be permitted by Egyptian authorities.
Beyond the discovery itself, the study demonstrates how particle physics can be used to investigate and preserve cultural world heritage without damaging ancient structures.
The Great Pyramid—standing about 146 meters (481 feet) tall—was built during the reign of Pharaoh Khufu between 2509 and 2483 BC. It remains the oldest of the Seven Wonders of the Ancient World.
Reference:
Morishima, K., Kuno, M., et al. “Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons.” Nature (2017). doi:10.1038/nature24647