Within the walls of Khufu’s Great Pyramid in Egypt, there is a secret corridor. Scientists confirmed its existence Thursday with research published in the Nature journal.
Though the pyramid has stood for more than 4,500 years, it “still holds many mysteries,” according to the article.
How were scientists able to find the hidden passageway?
The story goes back to 2016, when the ScanPyramids team of the Heritage Innovation Preservation non-profit began studying the pyramid. A technique called cosmic-ray muon radiography was used for the project pyramid. This technique is non-destructive, according to the research authors.
“We have investigated the internal structure of Khufu’s Pyramid using a technique based on the observation of cosmic-ray muons,” they explained. “Matter naturally absorbs a fraction of these muons coming from the atmosphere, this fraction is determined by the thickness and by density of the probed object. The measurement of the muon flux in a given direction then provides a direct estimate of the mean density in that direction.”
According to Egypt’s Ministry of Tourism and Antiquities, the Great Pyramid – a tomb built for King Khufu out of limestone – was the tallest structure in the world for 3,800 years. It is the last surviving member of the Seven Wonders of the Ancient World and it took at least a decade to build.
“To this day, it is not entirely certain how this was done,” the ministry said.
Inside the pyramid, there are three chambers “one cut into the bedrock underneath, and two high up within the masonry itself, a feature that no other pyramid possesses,” according to the ministry. “The sarcophagus in which Khufu was once laid to rest can still be seen in the upper of these two rooms, the King’s Chamber. This room is accessed through the Grand Gallery, a majestic corbelled ascending passage, and a masterpiece of ancient engineering and architecture.”
An architectural feature called a Chevron, which researchers describe as “a stone slab with a gabled structure” can be found inside the pyramid as well. Chevron has been found in the King’s Chamber, Queen’s Chamber and the North Face of the pyramid.
“This structure is slightly excavated from the surface of the pyramid and is thought to have been originally hidden inside the surface of the pyramid,” researchers said. Additionally, scientists believe Khufu’s Pyramid is the first pyramid to use the Chevron technique to cover internal structures.
Using measurements determined by the cosmic-ray muon radiography process, scientists are able to create maps of the “inner structure of an object,” such as the Great Pyramid. When the ScanPyramids team analyzed the pyramid, they discovered a “void” behind the North Face Chevron and named it the ScanPyramids North Face Corridor (NFC).
Part of the measurement process included use of nuclear emulsion film, “a photographic film-type particle detector that can record the trajectory of a charged particle without electric power supply,” made at Nagoya University in Japan. These nuclear emulsion films were installed from over a period of years beginning in 2016.
They were developed in a darkroom at the Grand Egyptian Museum Conservation Center at Cairo and transported to the university for analysis with an automated nuclear emulsion scanning system called Hyper Track Selector. Telescopes designed and operated by CEA and made of micro-pattern gaseous detectors called multiplexed Micromegas were also part of the process.
A detailed description of the research process is included in the Nature article. Ultimately, researchers observed “a corridor-shaped structure” around 30 feet long, 6 feet wide and 6 feet tall behind the Chevron zone on the North Face using the cosmic-ray muon radiography technique.
“The construction process of the oldest of the seven wonders of the ancient world is one of the most important archaeological mysteries,” said the research article. “Any discovery of previously unknown internal structures could contribute to the knowledge on the construction of this Pyramid.”
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