The Great Pyramid of Giza is one of the world’s most iconic and cherished monuments. But though this ancient structure is instantly recognizable from the outside, its interior is still filled with mysteries, including newly-discovered hidden chambers that have likely remained unexplored since they were built 4,500 years ago.
Now, scientists involved with the Exploring the Great Pyramid (EGP) Mission plan to use particles forged in outer space collisions, known as cosmic ray muons, to peer inside this monument and resolve its inner structure with unprecedented detail, potentially even detecting artifacts in its secret rooms.
The mission follows in the footsteps of the ScanPyramids project, another muon-based study that recently discovered large voids inside the Great Pyramid, marking the first time that a major feature of the monument had been revealed in over a century. However, the EGP’s next-generation muon telescope would deliver “upwards of 100 times the sensitivity” of the ScanPyramids project and “will, for the first time, produce a true tomographic image of such a large structure,” according to a study that was recently published in the Journal of Advanced Instrumentation in Science.
“The pyramids of the Giza plateau have fascinated visitors since ancient times and are the last of the Seven Wonders of the ancient world still standing,” said a team led by Alan Bross, a staff scientist at Fermi National Accelerator Laboratory in Illinois, in the study. “The Exploring the Great Pyramid (EGP) Mission presents the potential to obtain entirely new results on the internal structure of the Great Pyramid by having the precision to measure differences in density.”
Bross and his colleagues have obtained permission to set up their equipment by the Egyptian Ministry of Tourism and Antiquities, though it will take a lot more time and funding to develop the huge detectors. However, the effort and patience demanded by the mission will pay off if it is able to map out the Great Pyramid, as the advanced detectors could potentially capture information about small artifacts in the hidden chambers, if they exist.
“It would depend on the amount of ‘artifact,’” noted Bross in an email to Motherboard. “This is not a study we have done yet (although we have now been asked this a number of times and will add it to our simulation menu), but if the quantity of material is large enough, we should be able to say that something is there and it is not an empty void. However, I do not think we will be able to say much about what the material is unless there is a large amount of heavy metal.”
In addition to probing the potential contents of the mysterious chambers, Bross and his team hope to discover new insights about the construction techniques used to make this impressive monument, which “are still relatively unknown with many untested concepts having been hypothesized,” according to the new study.
“One of the fundamental questions is how the upper part of the pyramid was constructed—is it all solid cut stone or fill?” Bross said. “A high-resolution tomographic image will be able to detect differences in density which can indicate areas in the upper part of the pyramid where fill-in material such a broken rock [or] sand may have been used instead of cut stone. Also, architectural features such as construction staging areas may be visible in the image which would be indicated by changes in density.”
These big potential revelations could be exposed with the help of very small muons, which are negatively-charged particles that rain down from the skies in such abundant numbers that a few dozen pass through your body every second. Cosmic ray muons are created by the intense collisions between cosmic rays, which are high-speed bits of atoms that originate outside of our solar system, and elements inside Earth’s atmosphere.
Because they are so ubiquitous and can travel through more robust structures than X-rays, muons are able to offer glimpses into environments that are usually impenetrable. Scientists have used them to probe these inaccessible spaces for decades; the Great Pyramid was itself first explored with this technique by the Nobel-Prize-winning physicist Luis Alvarez in the 1960s.
As this field of muon tomography has matured, the pace of discoveries has accelerated, culminating in the amazing detection of the so-called “ScanPyramids’ Big Void” in 2017. This previously unknown chamber is located above a corridor called the Grand Gallery, and is at least 100 feet wide and 20 feet high. ScanPyramids also detected a smaller corridor-like cavity under the north side of the pyramid.
The pioneering project proved that there is much left to be discovered at the Great Pyramid, and the EGP mission has taken up the mantle with a plan to deploy far more sensitive detectors around the monument. Where ScanPyramids set up small handheld devices to capture muons in an accessible chamber inside the pyramid, the modular detectors envisioned by the EGP mission will be housed in giant shipping containers that will capture trillions of muons as they move around the outside perimeter of the pyramid.
“The Exploring the Great Pyramid Mission takes a different approach to imaging large structures with cosmic-ray muons,” the team said in the study. “The use of very large muon telescopes placed outside the structure, in our case the Great Pyramid of Khufu on the Giza plateau, can produce much higher resolution images due to the large number of detected muons.”
“In addition, by moving the telescopes around the base of the pyramid, true tomographic image reconstruction can be performed for the first time,” the researchers noted. “The detector technology employed in the telescopes is well established and prototyping of specific components has already begun.”
Though the recent discoveries by ScanPyramids galvanized the EGP mission team, the origins of their concept dates back over a decade, many years before the hidden chambers were detected in the pyramid.
“I started talking with [archaeologist] Mark Lehner back in 2010 about the idea of a large muon telescope to image the Great Pyramid after I returned from a conference in Egypt,” Bross said. “The basic ideas were described in a draft paper in 2012, but we never finished that paper due to lack of resources to fully carry out the simulation work.”
Lehner raised the prospect of an advanced muon telescope again in 2017, and Bross got the green light to pursue the EGP simulation work from Fermilab’s director Nigel Lockyer. The team was able to raise seed funding from both Fermilab and the University of Chicago’s Big Ideas Generator to complete the new study, which proves that the concept would work.
Bross estimates that it would take about two to three years to build the telescope and three years to image the pyramid in full resolution, a task that involves capturing about 100 trillion muons.
Since there are no plans to invasively burrow further into the pyramid, these muon scans are the best way to open a window into the newly discovered rooms of this incredible ancient monument—and into other tantalizing spaces.
“After the Great Pyramid, performing a scan on the second Giza Pyramid of Khafre would be high on the list,” Bross noted. “Scanning older pyramids, such as the Red Pyramid at Dahshur would yield interesting information on how the construction techniques evolved over the centuries. We have also discussed moving to the Valley of the Kings to look for undiscovered tombs.”
Time will tell if the voids within the Great Pyramid were utilitarian storage spaces or if they hold something more scintillating, such as the tomb of a bygone pharaoh. But the fact that these mysteries are being unraveled with the help of cosmic rays from exploding stars and distant galaxies may have seemed fitting to the culture that made these monuments, as ancient Egyptians believed the night sky was filled with profound insights and lost ancestors.
Update: This article has been updated with comments from study lead author Alan Bross, a staff scientist at Fermilab.