We all have heard of rain shower but have you ever heard of an air shower? The phenomenon is scientific, of course, and takes us back to the mysterious particles from outside the Solar system, that is, the cosmic rays. The story is a follow up on SS #27: The Mysterious Particles and is brought to you by Hariharan, a researcher at Cosmic Ray Laboratory in Ooty.

Narrator: Hariharan


Hey there and welcome to Hello Educator.


Today’s episode is from Mango Science Radio. The episode is from Hariharan. Hariharan is a researcher with Cosmic Ray Laboratory, Ooty. In the science story episode number 27, he had spoken about the mysterious particles. This episode is a follow-up of science story number 27. If you have not heard that particular episode I would suggest you do that. The link will be in the description. For the ones who have listened to it already, here’s the second part. It is titled ‘The Mysterious Particles That Travel To Earth’

00:58  Hi everybody, this is Hariharan. I hope you all are staying safe. Today, I have come up with another interesting topic. In the last episode, I gave an introduction about the mysterious particles in the universe known as cosmic rays. Hope you all enjoyed it. So let me guess, now you want to know what happens next, right? I have titled this episode ‘The Grand Tour of Mysterious Particles to the Earth’.

01:23  The universe is really vast. The cosmic ray particles originate somewhere and they keep on wandering for millions of years. At some point, they reach the vicinity of the Earth. Now, let me bring in a chunk of information. We know already that the Earth is covered with an atmosphere having multiple layers. The atmosphere consists of a mixture of gases. It comprises around 78% nitrogen, 21% oxygen and 1% combines carbon dioxide, carbon monoxide, and many other gases.

01:54  An imaginary line called the common line, which is about a hundred kilometres from the surface, defines the boundary of the atmosphere from outer space. Although we know these details, we never thought that our Earth’s atmosphere plays an important role in the journey of these mysterious particles. Here comes the interesting part. When these cosmic ray particles enter into the atmosphere, they collide with the atmospheric gas molecules. It is most likely to collide with nitrogen because they’re large in number. During the collision, they break the nucleus and scatter the protons and neutrons present inside. I’ll give an example to visualize this.

02:34  Imagine a thin bag consists of a large number of small balls and is hanging in the air. Now you hit this bag with another ball at high speed. The back tears off and all the balls are scattered in the space, right? This is exactly the same thing that happens in a cosmic ray collision with air molecules. Now, each of the scattered protons and neutrons further collides with the other molecules in the atmosphere and it continues like a chain reaction. It also produces more new particles like pions, ions, muons, electrons, etc.

03:09  At the surface, a large number of particles can be observed for a given cosmic ray particle. This entire process is known as ‘extensive air shower’. You may think this name sounds strange. Imagine the bathroom shower, how it expands from the top to bottom. It is a similar phenomenon happening with the air molecules; that is why it is called an air shower. In the process, it produces more than a billion particles for one highly energetic cosmic ray shower. Similarly, a low energy cosmic ray shower may not even reach the surface. It may die in the atmosphere itself.

03:47  But remember, the number of particles at the surface for a given cosmic ray depends on numerous factors like the type of the cosmic ray, its energy, incident direction, collision altitude, atmospheric composition, etc. It is like gambling of nature. Observing and studying the secondary particles allows us to study the nature of the incoming cosmic ray. Around the world, there are many experiments that employ this technique to study these mysterious particles.

04:19  I hope you all have enjoyed this episode. I will meet you again with another episode about capturing these mysterious particles. Hold on. Before I go, let me trigger your mind with another information. We all know that beautiful phenomena called Aurora Borealis and Aurora Australis or commonly known as Polar lights. What if I tell you that the polar lights are caused by these mysterious particles? I will bring the story in the subsequent episodes. Stay connected, stay safe. Bye.

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Music by Karthikeyan KC