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I believe that at least one of the reasons why radiation is so scary is that it is invisible (and of course potentially deadly). This invisible “threat” can be as terrible as the fallout from Chernobyl or as harmless as the output of cell phones.

However, science does a great job of taking the invisible and making it visible. In fact, there is a relatively simple way that we can reveal radiation. All we need is a device called a cloud chamber.

Making the Invisible Visible

Radiation may be invisible, but it is not magic. With an application of the right medium and an understanding of the physics involved, we can (indirectly) see radiation happening in real-time. Get your mind blown and then stick around for the science.

—More details on the YouTube page

The Science

So what is happening here? A cloud chamber in its simplest form is an enclosed space filled with supersaturated water vapor or alcohol. To get the vapors to this supersaturated state, the space is cooled down to very low temperatures (either electrically or with a material like dry ice). In this state, more water or alcohol is dissolved in the air than would be typically found in a gas at the same pressure.

In a supersaturated vapor, droplet formation is easy. This is how rain drops in clouds form. There is so much water dissolved in the air that any particles (like dust or ice) that the vapor can condense around forms water droplets (i.e. rain).

The same process is happening inside a cloud chamber. To make this analogy work, what is the vapor in the chamber condensing around, forming the vapor trails that we see in the videos above? Well, what makes a substance radioactive is that it shoots off particles of itself in a process called radioactive decay. For example, in the first video above, the radioactive substance that is used is Lead 210. This is an unstable form of lead which will decay into a more stable form. To do this, Lead 210 (and all other radioactive substances) emits particles of itself off into space, making a large and unstable atom a smaller and more stable one.

Radioactive substances typically emit two types of radiation: alpha and beta particles. Alpha particles are essentially the nuclei of helium atoms (2 protons and 2 neutrons) while beta particles are electrons. Each of which reduce the weight and size of the radioactive atom, making it more stable.

So what is making the trails in the chamber? This alpha and beta particle decay described above is shooting out from the radioactive material into the chamber. At the time when the particles collide with the water or alcohol vapor, the particles have enough energy to remove electrons from the matter they collide with. And when an atom loses an electron, it becomes an ion. This is why high energy radioactive material is said to produce ionizing radiation.

Creating what we see in the videos above, the decay particles leave a trail of ionized atoms/molecules in their wake, and this is what the supersaturated vapor condenses around. Like the ice or dust in a rain cloud which makes rain droplets, these ions allow the vapor to condense, making a visible trail out of droplets.

Radiation All Around Us

So that’s what we are actually seeing: the radioactive material in the videos is shooting off highly charged particles that create a trail of ions that in turn allow vapor to condense into a trail.

This is how we can make visible the invisible. Just think of the first scientist (Charles Thomson Rees Wilson) who saw this phenomena. How fascinating it must have been to allow our senses to witness radiation. You can find more videos like the ones above if you are interested, and better yet, cloud chambers are simple enough to make on your own! (Given that you can get the right materials).

Even though you have the instructions, you may not be able to get your hands on a radioactive substance (and if you aren’t sure on how to safely handle them, I wouldn’t recommend it). Interestingly enough, there is radioactivity all around you! Some of the more sensitive cloud chambers are able to visualize cosmic radiation, or the radiation produced in space that is constantly whizzing around us on Earth. You can see this in the video below:

It’s just as amazing to see the ever-present radiation coming into our lives from space. If you’re feeling up to it, get your own materials and do some science!