Radioactive Gas in a Cloud Chamber: A Wilson cloud chamber is a particle detector used for visualizing the passage of ionizing radiation using a sealed container containing supersaturated water or alcohol vapor. In this example, the radioactive isotope is Radon-220 gas that decays into polonium and then lead. The V-shaped trails are produced by two alpha particles from the two decay events. Source: Periodic Videos #science #physics #CloudChamber #GIF