The Great Pyramid of Giza is arguably the most iconic structure ever built by humans. Ancient civilizations created archaeological icons testifying to their greatness and resilience. But in some respects the Great Pyramid stands apart. Of the seven wonders of the ancient world, only the Great Pyramid has remained relatively intact.
A team of scientists will use advances in high energy physics (HIP) to scan the Great Pyramid of Khufu at Giza using cosmic ray muons. They want to look deeper into the Great Pyramid than ever before and map out its internal structure. The effort is called the Explore the Great Pyramid (EGP) mission.
The Great Pyramid of Giza has been standing since the 26th century BC. This is the tomb of Pharaoh Khufu, also known as Cheops. The construction took about 27 years and it was built from approximately 2.3 million blocks of stone – a combination of limestone and granite – with a total weight of about 6 million tons. For over 3,800 years, it was the tallest man-made structure in the world. Now we see only the basic structure of the core of the Great Pyramid. The smooth white limestone shell has been removed over time.
The Great Pyramid has been well studied, and archaeologists have been mapping the internal structure over the years. The pyramid and the ground below it contain different chambers and passageways. The room of Khufu (Cheops) is located approximately in the center of the pyramid.
Recently, some high-tech methods have been used by archaeological teams to more closely examine the insides of the pyramids. In the late 1960s, American physicist Luis Alvarez and his team used muon tomography to scan the inside of the pyramid. Alvarez reported in 1969 that they had explored 19% of the pyramid and found no new chambers.
In 2016-2017, the ScanPyramids team used non-invasive methods to study the Great Pyramid. Like Alvarez before them, they used muon tomography as well as infrared thermography and other instruments. Their most significant discovery is the “Great Void”, a massive void above the Grand Gallery. The discovery was published in the journal Nature and is considered one of the most significant scientific discoveries of that year.
Muons are elementary particles similar to electrons, but more massive. They are used in tomography because they penetrate deeply into structures. Deeper than even X-rays can.
Cosmic ray muons are created when high-energy particles known as cosmic rays crash into Earth’s atmosphere. Cosmic rays are fragments of atoms – high-energy protons and atomic nuclei – that are constantly rushing to Earth from the Sun, outside the solar system and outside the galaxy. When these particles collide with the Earth’s atmosphere, the collision produces streams of secondary particles. Some of these particles are muons.
Muons are unstable and decay in just a couple of microseconds or millionths of a second. But they are moving at close to the speed of light, and at such a high speed they can penetrate deep before they disintegrate. There is an endless source of muons from cosmic rays that constantly bombard the Earth. The task of muon tomography is to efficiently measure muons.
Muon tomography is used in a variety of applications, such as checking shipping containers for contraband. Recent technological innovations in muon tomography increase its power and lead to new applications. For example, scientists in Italy will use muon tomography to image the inside of Mount Vesuvius, hoping to understand when it might erupt again.
The Explore the Great Pyramid (EGP) mission is using muon tomography to take the next step in imaging the Great Pyramid. Like the ScanPyramids before them, EGP will use muon tomography to image the interior of the structure. But EGP says their muon telescope system will be 100 times more powerful than previous muon imaging. “We plan to install a telescope system with a sensitivity 100 times greater than the equipment recently used in the Great Pyramid that will image muons from virtually all angles and for the first time provide a true tomographic image of such a large structure,” they write in a paper explaining mission.
EGP will use very large telescope sensors moved to different locations outside the Great Pyramid. The detectors will be assembled in temperature controlled shipping containers for easy transport. Each unit will be 12 meters long, 2.4 meters wide and 2.9 meters high (40 feet long, 8 feet wide and 9.5 feet high). Their simulations used two muon telescopes, and each telescope consists of four containers.
There are five critical points in the EGP mission:
- Make a detailed analysis of the entire internal structure, which not only distinguishes between stone and air, but can also measure changes in density.
- Answer questions about construction methods by being able to see relatively small structural gaps.
- The large size of the telescope system not only results in increased resolution, but also allows for rapid acquisition of data, minimizing the required viewing time in situ. The EGP team expects two years of review.
- The telescope is highly modular in nature. This makes it easy to reconfigure and deploy to another site for future research.
- From a technical standpoint, the proposed system uses technology that has been largely designed and tested and is a low risk approach.
The EGP is still building prototype telescopes and determining which data processing methods they will use. Along the way, they do modeling and other work to prepare for the mission. One of the important points is how they combine all these muons into a tomographic image.
But the team is confident in the work done and happy with their new approach. EGP says that their efforts will allow for the first time to create an actual tomographic image of the Great Pyramid, rather than a two-dimensional image.
“The Great Pyramid Exploration mission takes a different approach to visualizing large structures using cosmic ray muons. The use of very large muon telescopes placed outside the structure, in our case the Great Pyramid of Khufu on the Giza Plateau, allows much higher resolution imaging due to the large number of muons detected. In addition, by moving telescopes around the base of the pyramid, for the first time, a true tomographic image reconstruction can be performed.”
Much of EGP’s work so far has been in data modeling. But they won’t start from scratch when they build the telescope. “The detector technology used in the telescopes is well established, and prototyping of specific components has already begun,” they write.
When ScanPyramids discovered the Big Void in 2017, it was big news. This also caused controversy. Egyptologist Zahi Hawass criticized the results. He told the New York Times that “they didn’t find anything… This article offers nothing to Egyptology. Zero.”
But most other Egyptologists accepted the discovery and its scientific nature. Physicists also supported the discovery. Particle physicist Lee Thompson told Science that: “The scientists ‘saw’ the void using three different muon detectors in three independent experiments, making their conclusion very robust.”
When scientists use state-of-the-art high-energy physics to explore one of humanity’s most ancient archaeological treasures, some drama is bound to happen. Some Egyptologists seem possessive and may view physicists as violators of their field. They may not like that physicists are using mysterious particles from space to lift the veil on our ancient past.
Looks like they’ll have to get used to it.
Originally published on Universe Today.
Reference: “Tomographic Muon Imaging of the Great Pyramid of Giza” by Alan D. Bross, EC Dukes, Ralph Ehrlich, Eric Fernandez, Sophie Dukes, Mohamed Ghobashi, Ishbel Jamieson, Patrick J. La Riviera, Mira Liu, Gregory Maruara, Nadine. Moeller, Anna Pla-Dalmau, Paul Rubinov, Omar Shohud, Philippe Vargas and Tabitha Welch February 16, 2022 Physics > Instruments and detectors.