Why in news?

• To analyse 14 kilometres long rampart, researchers deployed a technique called muon tomography or muography, which uses muons to generate three-dimensional images of such large structures.

What are Muons?

• Muons are subatomic particles raining from space.
• The muon was discovered as a constituent of cosmic-ray particle “showers” in 1936 by the American physicists Carl D. Andersonand Seth Neddermeyer.
• They are created when the particles in Earth’s atmosphere collide with cosmic rays — clusters of high-energy particles that move through space at just below the speed of light.
• It has two forms, the negatively charged muon and its positively charged antiparticle.
• These particles resemble electrons but are 207 times as massive. Therefore, they are sometimes called “fat electrons”.
• Muons are so heavy, they can travel through hundreds of metres of rock or other matter before getting absorbed or decaying into electrons and neutrinos
• They are highly unstable and exist for just 2.2 microseconds.

What is muon tomography?

• Although muon tomography was first used in the 1960s, it has only recently gained widespread use among researchers, particularly in archaeology.
• It is conceptually similar to X-ray but capable of scanning much larger and wider structures, owing to the penetration power of muons.
• All that is required is to place a muon detector underneath, within, or near the object of interest.
• The detector then tracks the number of muons going through the object from different directions, to form a three-dimensional image.
• The image is then compared with a muon image of the “free sky.” This indicates how many muons have been blocked. The final picture is essentially a shadow of the object, in the light of cosmic muons.”