Scientists use outer space particles to examine the fortress wall of Xi’an city: What are muons and how are they used to Analyze large structures

General Studies Paper 3

Context:

• As per a new study, researchers are examining the fortress wall of Xi’an, an ancient city in China, by using tiny outer space particles called muons that can penetrate hundreds of metres of stone surfaces.

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.
• According to Scientific American magazine, about 10,000 muons reach every square metre of the Earth’s surface a minute.
• Features:Muons 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. In comparison, electrons can penetrate through only a few centimetres.
• Muons are also highly unstable and exist for just 2.2 microseconds.

What is muon tomography or muography?

• 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.
• 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.

Uses of Muon Topography

• Muon tomography was first used in the 1960s, it has only recently gained widespread use among researchers, particularly in archaeology.
• Apart from archaeology, muography has also found use in customs security, internal imaging of volcanoes and others. Around 2015, scientists used the technique to look inside the Fukushima nuclear reactors after the 2011 earthquake and tsunami in Japan.