Photographs of tracks made by ionised particles in a cloud chamber, c 1920s.
© Science Museum / Science & Society Picture Library
These glas negative photographs were taken in a cloud chamber. Cloud chambers are used for tracking the movements of ionised subatomic particles. Within the chamber, fast-moving particles collide with air or gas molecules and show as visible tracks. Photographs of these tracks reveal information about ionised particles and radiation. The cloud chamber was invented in 1897 by the English scientist Charles Thomson Rees Wilson (1869-1959).