Particle tracks and historical cosmology. Computer illustration of subatomic particle tracks (white) seen with a historical depiction of the structure of the universe and a head. The tracks result from particles moving through a bubble chamber containing a superheated liquid. The disturbance of the liquid by the particles causes it to boil, so that tracks of minute bubbles are left in the wake of the particles which can be photographed and studied. Old cosmological theories placed the Earth at the centre of the universe, but physics has corrected misconceptions such as this. Particle physics has revealed the basic structure of the atoms from which everything is made.