On what basis was the Photon determined massless? any proof or Test?

Answer 1

Good question. In truth, most experiments say photons are massless because they behave like a massless particle in most experiments. However, if energy is the basis for all matter and photons consist of energy, there is the possibility it has some mass that allows it to act like a particle while still moving in a wave of energy. Refer to the link for the tests.

Answer 2

Right--refer to Wikipedia, but then don't read that Wikipedia defines a photon as a massles particle. Great.

As "massless" particles, photons move at a speed of 2.998×10^8 m/s, which is represented by the symbol c (often called the speed of light in vacuum). Based on the theory of special relativity, photons always move at a constant speed with respect to all observers, regardless of the observers' own velocities. (Wikipedia)

DakkonA wins.

Answer 3

An electron when moving with the speed nearly equal to C, has a kinetic energy (m - m0) C^2, where m is the relativistic mass of the electron and m0 is its rest mass.

When all its kinetic energy is transformed into some other energy,
we are left with an energy mo C^2.

It is the rest mass of the electron or its internal energy.

In the case of photon which is an energy bundle, has kinetic energy, given by hn, where h is the Planck’s constant and n is its frequency.

When its energy is absorbed or when its kinetic energy is fully utilized, (part of its energy cannot be utilized) no energy is left out. That is, it has no internal energy unlike electron.

If we speak of internal energy and kinetic energy, then there is no need to speak of mass.

Mass is no longer the “mass” in classical physics.

It is the potential or residual or internal energy of material. But Photon is full of energy and energy alone; it has no potential or residual or internal energy.


Any energy can be thought of having mass, but the question is how much will be its internal mass (energy) when it is brought to rest.

Answer 4

I agree with 'fullbony'. Photons in absolute sense are not massless because of the energy mass relationship.

Answer 5

to answer your question, one must define "mass".

according to Einstein's special relativity, energy is equal to mass x speed of light squared. alternatively, energy is the same as mass, differing only in its perception.

strictly speaking, photons have mass as they have momentum, but it is unlike the mass of an electron. its all dependent on how you observe energy.

photons are deemed "massless" because they always moving at the speed of light ( which no entity with a conventional mass can move at ) . in fact, entities which travel below the speed of light are deemed as having a "rest mass" ( the mass we normally think of ). mass is only a sort of "frozen form" of energy.

fundamentally, all entities can be divided as those which travel at the speed of light vs. those that travel slower than that. according to relativity, NO mass can move the speed of light.

in addition to the wealth of experimental data that supports the massless photon, general relativity firmly asserts that photons should have no mass.

simply put, if something travels at the speed of light, it CANNOT have mass.

Answer 6

For one thing, the photon moves at the speed of light, which is only possible for things without mass.