Question

How a massless thing(photon) can exist?

Answer 1

Inparticle physics, amassless particleis anelementary particlewhoseinvariant massis zero. The two known massless particles are bothgauge bosons: thephoton(carrier ofelectromagnetism) and thegluon(carrier of thestrong force).
The behavior of massless particles is understood by virtue ofspecial relativity. For example, these particles must always move at thespeed of light.
Massless particles are known to experience the same gravitational acceleration as other particles (which provides empirical evidence for theequivalence principle) because they do haverelativistic mass, which is what acts as the gravity charge. Thus, perpendicular components of forces acting on massless particles simply change their direction of motion, the angle change in radians beingGM/rc²withgravitational lensing, a result predicted bygeneral relativity. The component of force parallel to the motion still affects the particle, but by changing the frequency rather than the speed. This is because themomentumof a massless particle depends only on frequency and direction, while the momentum of low speed massive objects depends on mass, speed, and direction