In particle physics, a massless particle is a particle whose invariant mass is zero. Currently, the only known massless particles are gauge bosons: the photon (carrier of electromagnetism) and the gluon (carrier of the strong force). However, gluons are never observed as free particles, since they are confined within hadrons.
Neutrinos were, until recently, thought to be either massless or have a small mass. Because neutrinos change flavour as they travel, at least two of them must have mass.
Read more about Massless Particle: Massless Particle Description, Special Relativity, Dynamics, Gravitons
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“Love is life. All, everything that I understand, I understand only because I love. Everything is, everything exists, only because I love. Everything is united by it alone. Love is God, and to die means that I, a particle of love, shall return to the general and eternal source.”
—Leo Tolstoy (1828–1910)