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Cosmic rays and the nature of solidity February 28, 2008

Posted by eyegillian in energy, learn, nature, science, space.
Tags: , , , , , , , , , , , , ,

cosmic raysWhen I visited the Ontario Science Centre recently, I became fascinated by the Cloud Chamber. I sat mesmerized, watching as particles zipped around like invisible jets, leaving quickly vanishing vapour trails behind. It was tough to get a photo that shows those ephemeral paths!

Here’s how it works: Cosmic rays are part of the natural radiation we are exposed to here on earth. As these radioactive particles pass through the air they collide with air molecules, detaching an electron from atom after atom, and leave behind a trail of ions. The ions are air molecules that have either lost an electron (leaving them with a positive charge) or picked up the freed electrons (giving them a negative charge). The cloud chamber contains super-saturated alcohol vapour, which clings in tiny drops to these ions to mark the trail.

Cosmic rays come mostly from protons in outer space. They continually bombard the earth and stream through everything that we would consider to be “solid”, including our bodies. We can’t see cosmic rays directly, but we can see the result of the rays’ interaction with the atmosphere in the display of the aurora borealis and aurora australis, for example.

When a cosmic ray enters the earth’s atmosphere, it collides with a nitrogen or oxygen atom in the air, creating a chain reaction which breaks apart the atoms and results in a shower of particles. Most of these particles have very low energy and decay or are absorbed into the atmosphere. The only particles that reach the ground are either very energetic or relatively stable. One such particle is the muon, a high-energy heavier version of the electron. At sea level, the flow of high-energy muons is about six muons per square inch per minute.

Now I’m not trying to assert any scientific thesis here; I’m sure any physicist could write ad infinitum about all these radioactive particles and the differences between electrons, ions, muons, protons, pions, etc. As a curious non-scientist, however, what I find particularly fascinating is the fact that a) there are so many types of “radiation” that are passing through our bodies every day; and b) that we are so permeable.

As I read about this phenomenon, some of what I learned in long-ago science classes comes back to me, how all the so-called solid objects which make up our world are not actually solid at all, but made up of a bunch of bouncing atoms. This brings a new kind of “seeing” to my observations of nature. And being actually able to “see” these speeding particles is a bonus; it somehow makes them a lot more real than anything in a school textbook.

particle trails

Photos by Seeing Is

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Related Links:
Build your own Cloud Chamber
Cosmic Extremes — a pdf pamphlet on cosmic rays
Cosmic Rays: A possible source



1. Richard - March 1, 2008

I also think it’s fascinating to think about all these subatomic particles going through our bodies all the time, completely unnoticed. There are some (neutrinos) that are virtually unstoppable, and because they have no charge and little or no mass, they are virtually undetectable too.

I think that teaching kids about things like this is the way to make a new generation take an interest in science, rather than teaching them about complicated equations to work out how fast a ball will be traveling if you drop it 100 feet and boring stuff like that.

2. eyegillian - March 3, 2008

Thanks for your comment, Richard. I remember my first experience going to the Ontario Science Centre as a child — on a rare visit to Toronto — and suddenly seeing how science could be really cool! Unfortunately, that feeling faded as soon as I hit the classroom again.

3. where music and science meet « Tin Can Beach - February 16, 2011

[…] At one point in the play, the characters talk about the visual trail left by particles in the cloud chamber, and I could suddenly picture exactly what they were talking about. We spent some time a few years ago watching the cloud chamber at the Ontario Science Centre and I even managed to take a few fuzzy photos; my observations are recorded in a old blog post here. […]

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