As per a new study published in the Journal of Applied Physics, researchers are examining the fortress wall of Xi’an, an ancient city in China, by using tiny outer space particles that can penetrate hundreds of metres of stone surfaces.
- Xi’an’s wall is 12 metres high and 18 metres thick.
- To analyse this 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. 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.
- About 10,000 muons reach every square metre of the Earth’s surface a minute. Although muons can travel deep into earth and stone, they are scattered or absorbed depending on the material they encounter.
- Counting the ones that pass through makes them useful for studying volcano interiors, scanning pyramids for hidden chambers and even searching for contraband stashed in containers impervious to X-rays.
- These particles resemble electrons but are 207 times as massive. Therefore, they are sometimes called “fat electrons”.
- Because 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,
- Though muons stream down continuously, their numbers are small enough that the researchers had to deploy six detectors for a week at a time to collect enough data for 3-D scans of the rampart.
- Muography is conceptually similar to X-ray but capable of scanning much larger and wider structures, owing to the penetration power of muons. As these high-energy particles are naturally produced and ubiquitous, all one needs to do is place a muon detector underneath, within or near the object of interest.
(Source: Indian Express)
