Every day the Earth is battered by high-energy radiation that streams into the solar system and slams into our planet's magnetic field. Many of these cosmic rays are the relic of death—like the iron in your blood or the calcium in your teeth, they were produced by supernovae. Using a surprisingly inexpensive device, says Joe Hanson in the video above, you can see these particles, or at least their aftereffects, with your own eyes.
A cloud chamber is a relatively simple yet powerful tool. The chamber contains alcohol vapor that's been supercooled—it's been made so cold that it should have condensed into liquid. When this supercooled alcohol vapor is hit by a cosmic ray it suddenly condenses, and you see this as a small line of clouds, says Andrew Foland for Cornell. The path the cloud track follows, says Foland, can tell you what you're seeing: a cloud with a sharp turn is a “muon decay,” while a track that suddenly branches is the sign that the cosmic ray hit an electron.
CERN, the folks behind the Large Hadron Collider, have a step-by-step guide to building your own cloud chamber.