All around you, and on every surface of the earth, there is radiation pummeling the atoms that make up the matter that we can see and feel. Even as you read this sentence, you are being bombarded by radiation. Pew! Pew!

But fear not, it’s completely normal. This background radiation is safe. And though it cannot be seen directly, you can build a cloud chamber to help you indirectly observe radiation and begin to understand it.

Target Grades: 9-12+

Content Areas: Physics, Engineering and Technology

Activity Type: Detect radiation, design radiation shielding

Time required: About 1 hour

Next Generation Science Standards: HS-PS1-8

Radiation is any type of wave or particle that transmits energy and includes things like ultraviolet light, alpha radiation (particles made up of two neutrons and two protons), sound (acoustic waves), and x-rays (electromagnetic waves). Radiation that transmits large amounts of energy, called high-energy radiation or ionizing radiation, can change or damage other materials and living cells that it comes into contact with. When describing radiation exposure from man-made sources of radiation like X-rays or nuclear energy plants, what is being described is ionizing radiation.

In small amounts, however, ionizing radiation does not do significant harm, and in fact, it’s a part of our everyday life. Ionizing radiation that naturally occurs on our planet is called background radiation and is a natural part of our planet’s environment. Background radiation can come from all kinds of things, including cosmic rays from outside our galaxy, radioactive materials in the earth like uranium and radon, and even radioactive materials in our body, such as certain kinds of potassium and carbon atoms.

Even though we can’t see these different kinds of radiation directly, we can indirectly observe them when they interact with substances that we can see. Interactions are often physical collisions between a radioactive particle or wave and a non-radioactive atom. Detecting radiation by looking for its interactions with atoms is similar to how you might indirectly observe wind: you can’t see wind itself, but you can see leaves, trees, or plastic bags move in the wind and deduce that the wind is there.