Archaeologists and physicists have achieved a breakthrough in historical exploration by using cosmic-ray muons to map subterranean structures in Jerusalem without traditional excavation. Cosmic rays are high-energy particles that collide with the Earth’s upper atmosphere, and the muons that result from this collision penetrate through the Earth’s crust at a consistent rate.As part of this investigation, researchers placed extremely sensitive miniaturised detectors inside ‘Jeremiah’s Cistern,’ located in the City of David, and measured the attenuation (or decrease in energy) of cosmic ray muons as they travelled through the surrounding rock and soil. The amount of energy lost when cosmic ray muons pass through a substance, such as empty caves, will be less than the amount of energy lost when they pass through a denser substance like solid rock, as noted in the Journal of Applied Physics. Therefore, the research team was able to successfully use this technique to identify underground voids and tunnels. This innovative, non-invasive ‘X-ray’ technology allows for the precise mapping of fragile archaeological sites while preserving their structural integrity for future generations.
Muon detection helps scientists map hidden structures beneath Jerusalem
According to the study published in the Armstrong Institute of Biblical Archaeology, Muon detection, a form of using cosmic rays as a source of illumination, is the basis for how muons pass through matter; muons get scattered or stopped in accordance with the density of the material they are passing through. By tracking those paths, scientists can make a three-dimensional density map of subsurface features. The current study is the first time that a custom-designed muon detector has been tested operationally in an archaeological historic environment, thus showing that this technology can successfully detect structural features beneath or behind complex rock-cut structures.
How LiDAR and Muon flux redefine site mapping
In order to validate their findings, the research team combined muon flux simulations with LiDAR scanning (a method that uses reflected laser light to create a digital model) as per the study noted in the Journal of Applied Physics. LiDAR provides a very accurate three-dimensional representation of the features of an object or space that can be seen, such as walls, floors, etc., whereas muons are a means of detecting that which cannot be seen, such as voids or chambers located zero to twenty feet below the surface of the ground. By layering the two types of data, archaeologists can locate and shape structures that would otherwise go undetected, and change the way in which excavations are conducted, as well as provide new information.
The future of discovery, refining detectors for global application
The innovative methodology developed by researchers from Tel Aviv University represents a paradigm change. The ability to scan entire archaeological sites in three dimensions before moving any earth could help prevent the destruction of delicate archaeological layers at a fraction of the cost of conventional excavation. As a result, researchers are currently developing large-scale, more capable detectors for the purpose of using them in various archaeological excavations throughout the world, to identify the hidden past and yet preserve the physical integrity of the ruins as they are found.
About the Author
