How did C.T.R. Wilson's cloud chamber work?
The operation of the cloud chamber is, at its heart, a matter of controlled condensation. We begin with a volume of air, carefully cleared of dust, which acts as vapor. This vapor is then cooled, typically by allowing it to expand rapidly, or by chilling the base of the chamber. This cooling creates a state of supersaturation, where the vapor holds more water than it normally could at that temperature. When an ionizing particle traverses this sensitive volume, it leaves a trail of ions. These ions, acting as condensation nuclei, promote the formation of tiny water droplets. Thus, the invisible path of the particle becomes beautifully visible as a line of mist. The evidence is in these tracks; they reveal the very existence and motion of these subatomic entities.
Ask Charles Thomson Rees Wilson the follow-up →