Cosmic Rays: Definition & Origin

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  • 0:01 Electromagnetic Radiation
  • 0:40 What are Cosmic Rays?
  • 2:39 Cosmic Ray Sources and…
  • 3:41 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will explain what cosmic rays are (including primary and secondary cosmic rays), where they come from, if you should be worried about them, and what you can do to protect yourself from them if need be.

Electromagnetic Radiation

Electromagnetic radiation is a form of energy that includes visible light. It comes to Earth from the farthest reaches of space. It is the reason why we can see the moon and twinkling stars, and feel the sun's heat. It allows for doctors to take X-rays and for you to microwave your food.

But there is another kind of energy lurking in the cosmos. It's zipping past and through you as you listen to me. It causes nuclear reactions, and its origins are quite mysterious.

This lesson will tell you what it's called, where we think it comes from, and some interesting things we know about it.

What Are Cosmic Rays?

The kind of energy I'm speaking of comes to us in the form of cosmic rays, extremely energetic particles (that is to say, ions and electrons) that travel through the cosmos at almost the speed of light. They were discovered by Victor F. Hess in 1912 during a balloon flight.

Cosmic rays found beyond Earth's atmosphere are called primary cosmic rays. Sometimes, these primary rays collide with Earth's atmosphere. When this happens, atoms that make up the gas in Earth's atmosphere are smashed apart into fragments which shower down onto Earth's surface. Particles produced from the collision of a primary cosmic ray with Earth's atmosphere are called secondary cosmic rays. These are the guys moving through you right now.

Should you be worried? Down at ground level, protected by Earth's atmosphere, the best evidence says that the chances of a health risk, including cancer risk from cosmic rays, are quite small. Earth's atmosphere encases you in a protective layer equivalent to 13 feet of concrete. Cosmic rays are a bigger threat to astronauts, who may not only be at an increased risk of cancer, but also permanent memory loss the more they are exposed to this stuff, a lot more than any person on Earth would be.

The good news is that preliminary research does show that antioxidants, like those found in berries, may help protect the cells in our bodies from the damaging effects of cosmic rays. So, go out and eat some berries. Chocolate-covered strawberries sound good right about now. I imagine because of this, astronauts flying off to Mars will now become a distinct kind of fruitarian, a berrytarian, to help protect themselves from cosmic rays. That word, 'berrytarian', probably hasn't existed until now. You're free to use it, however.

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