Fermions and bosons


Elementary particles are divided into two large families according to the value of the spin, a physical quantity that , in simple terms, refers to the rotation of a particle around its own axis. Particles which, in certain units, have the semi-integer value of spin are called fermions. Fermions obey to the Exclusion Principle: it is impossible for two atoms in a solid to be in the same state and therefore to have the same energy. All known matter consists of fermions, which are responsible for the mass that is detectable in nature. The Pauli exclusion principle is responsible for the fact that ordinary matter is stable and occupies volume: the electrons of each atom cannot all fall into the lowest energy orbital and must occupy successively larger shells. Atoms, therefore, occupy volume and cannot be squeezed too closely


In contrast, particles with an integer spin, such as photons, follow the Bose-Einstein statistic and are called “bosons” in honour of the Indian physicist Satyendra Nath Bose who formulated it. He sent his results to Albert Einstein, who understood its importance and had them published. Bosons, not following the Pauli exclusion principle, can occupy the same energy state in unlimited numbers at the same time, and at low temperatures they tend to cluster in the same low energy level forming a Bose-Einstein condensate. The Bose-Einstein statistic is particularly useful in the study of gases. All elementary particles mediating fundamental forces are bosons. All compound particles that contain an even number of fermions are bosons.

This interactive installation is intended to provide an impressive demonstration of the behaviour of bosons that can crowd the same quantum state in large numbers.