Photon
A photon (light particle) is the quantum of energy as a form of electromagnetic radiation.
Explanation
A photon is the carrier of electromagnetism. Photons have spin 1 and are thus gauge bosons.
G a u g e b o s o n U(1) ɣ
photon
Mass
Light particles move at the speed of light c. From special relativity it follows that a particle with a rest mass greater than 0 never can reach the speed of light. A light particle has no rest mass, and is therefor a massless particle.
Time
A light particle does not desintegrate and is therefore completely stable. According to the special theory of relativity the local time of a light particle stands still, so a light particle does not get the time to fall apart.
Polarization
A photon can be polarized horizontally or vertically. Until the polarization is measured, the photon is in a superposition of these two states, and we can write this as
|ψ⟩ = α |H⟩ + β |V⟩
in which α and β are complex probability amplitudes. The probability that you measure a photon with status |H⟩ is |α|^{2} and that you measure the status |V⟩ is |β|^{2}, because it applies
|α|^{2} + |β|^{2} = 1
Additional information
The concept of the photon was developed by Albert Einstein in 1905. The name of "photon" is attributed to Gilbert N. Lewis (1926).