A groundbreaking advancement at Tel Aviv University has introduced a revolutionary method for archaeological exploration, harnessing the power of cosmic radiation detectors to identify hidden underground spaces. This pioneering approach capitalizes on the detection of muons, subatomic particles generated when cosmic rays interact with Earth’s atmosphere. Muons possess the extraordinary ability to penetrate deep beneath the surface, gradually losing energy and coming to rest after traversing various materials. By analyzing muon flux variations, archaeologists can effectively map subterranean voids such as ancient tunnels, cavities, and water channels, marking a significant leap forward in archaeological surveying techniques.
The core principle behind this technology lies in the unique properties of muons, which are elementary particles similar to electrons but approximately 207 times heavier. They originate in the upper atmosphere when high-energy cosmic protons collide with molecular nuclei, producing pions that decay rapidly into muons. Despite their fleeting intrinsic lifetime of just 2.2 microseconds, muons travel at velocities nearing the speed of light, enabling many to reach and penetrate the Earth’s surface. This phenomenon is further explained by Einstein’s theory of special relativity, where time dilation allows muons to survive long enough to be detected underground.
Unlike electrons, muons feature a remarkable capacity to traverse dense materials. While electrons are typically impeded and halted after penetrating only a few centimeters of soil or rock, muons gradually lose energy and can pass through several meters, even reaching depths of up to 100 meters depending on their initial energy levels. This slow attenuation is crucial for archaeological applications, as variations in muon flux correspond directly to differences in the density and composition of subsurface structures. Areas containing voids or less dense materials cause less muon absorption, resulting in a higher measured flux that points to the presence of underground cavities.
The analogy often employed to explain this process is reminiscent of medical X-ray imaging, where dense bone tissue blocks X-rays, casting shadows on the image, while softer tissues allow passage of the rays. Similarly, in muon tomography, the muons serve as a natural, cosmic X-ray beam, the detector functions as the capturing camera, and the underground geological formations act as the absorptive tissues. This framework enables comprehensive three-dimensional imaging of hidden features below the surface, without disturbing or excavating the site.
In an impressive demonstration of the technology’s potential, the research team conducted their experiments at the City of David archaeological site in Jerusalem, utilizing a rock-hewn chamber known as Jeremiah’s Cistern. By integrating high-resolution LiDAR scanning data of the cistern’s interior with sophisticated computer simulations of muon flux attenuation, the scientists successfully mapped structural anomalies indicative of hidden subsurface features. This interdisciplinary methodology validates the feasibility of muon tomography for archaeological imaging and presents a new avenue for non-invasive exploration.
The study was spearheaded by Professor Erez Etzion from Tel Aviv University’s Raymond and Beverly Sackler School of Physics and Astronomy and Professor Oded Lipschits from the university’s Jacob M. Alkow Department of Archaeology and Ancient Near Eastern Cultures. The diverse team also included experts from Israel’s Rafael Advanced Defense Systems and the Israel Antiquities Authority, reflecting the highly collaborative nature of this research. Their findings were published in the prestigious Journal of Applied Physics, marking a milestone in applied archaeological science.
One critical challenge addressed by the research was the adaptation of muon detectors for fieldwork in archaeological contexts. Unlike controlled laboratory environments, excavation sites present logistical difficulties including limited power supply, variable temperature and humidity conditions, and cumbersome terrain. To overcome these hurdles, the team engineered compact, mobile, and power-efficient muon detectors capable of operating robustly in situ. These advances enable prolonged monitoring and data collection essential for creating detailed subsurface maps.
The muon detection technique holds promise especially in regions like the Judean Foothills, where archaeological sites are layered with hard limestone overlying softer chalk. Historically, ancient inhabitants exploited this geology by carving out extensive networks of reservoirs and other subterranean structures, which remain largely invisible to conventional survey methods. Now, the ability to identify these “hidden cavities” could revolutionize the manner in which archaeological excavation and preservation are planned, prioritizing sites with known subsurface features.
Looking ahead, the research team envisions integrating artificial intelligence and machine learning algorithms to interpret the vast quantities of muon detection data collected across multiple detectors. This computational approach aims to reconstruct intricate three-dimensional images of entire archaeological sites, synthesizing raw muon flux readings with geological and structural information. The next phase of application is planned for Tel Azekah, a strategic and historically significant site situated in the heart of the Judean Hills overlooking the Elah Valley.
While the concept of muon radiography is not entirely new—it dates back to the 1960s when scientists sought hidden chambers in the Egyptian pyramids—this study represents a transformative advancement by tailoring the technology specifically for archaeology with enhanced mobility, durability, and sensitivity. The team’s innovation lies in practical deployment within challenging excavation settings and real-time data analysis, expanding the scope and precision of underground exploration beyond previous limits.
Moreover, the muon detection method offers enormous potential beyond archaeology. Its sensitivity to density variations can aid geological surveys, civil engineering projects, and even homeland security by detecting hidden tunnels or voids beneath critical infrastructures. By refining detector design and improving data processing techniques, the range and resolution of muon imaging are expected to grow, propelling this cosmic particle-based technology into wider scientific and practical arenas.
To summarize, this pioneering research fosters a new era in archaeological methodology by exploiting the naturally occurring muon radiation shower that the Earth continually receives. Through detecting and analyzing changes in muon absorption by subsurface materials, archaeologists now have a powerful, non-invasive tool to visualize hidden spaces beneath ancient sites. This innovation not only preserves the integrity of invaluable historical locations but also paves the way for unprecedented discoveries waiting beneath the ground.
Subject of Research: Muon tomography for archaeological subsurface imaging
Article Title: First Demonstration of Underground Muon Imaging at the City of David Archaeological Site
News Publication Date: Information not provided in the source content
Web References: https://pubs.aip.org/aip/jap/article/138/8/084504/3361099/First-demonstration-of-underground-muon-imaging-at
References: Journal of Applied Physics, DOI: 10.1063/5.0273376
Image Credits: Illustration from the original article linked on EurekAlert.org
Keywords: Archaeology, Cosmic rays, Muon tomography, Subsurface imaging, Particle physics, Muon detectors, LiDAR integration, Non-invasive surveying, Judean Foothills, Tel Aviv University
