If there is no absolute frame of reference where aparticle is at rest than why fotons zero speed be massless?

Answer 1

Mass and energy are competely equivalent concepts, this comes from the E=mc^2 equation. Now a photon has momentum and therefore Kinetic energy, using the equivalence I mentioned above, photons has mass.
Now what would happen if we could find a photon is at rest?(I use this as a metaphor, A photon at rest would not be a photon!)
Then we would measure it's velocity to be zero, and so will be it's momentum and therefore it's energy and as a result its mass would be zero.
Note that if we stop a photon, it wont be a photon anymore but whatever the photon be transformed to, will have the same mass-energy as the initial photon.

Answer 2

the speed of light is a continuing and is not relative to any inertial body of reference. If i'm pointing a flashlight ahead and that i'm vacationing on the speed of light, that doesn't advise that the mild vacationing from the proper of the flashlight is shifting at two times the speed of light. the speed of light is an similar no be counted the position you're or what you're doing.

Answer 3

Photons have no mass, period. See my answer to your other question on the subject.

There IS a reference frame where the photon is at rest: its own frame. You're never moving relative to yourself.

This is why we only care about invariant (rest) mass. Two different observers may measure the relativistic mass differently, therefore it doesn't really add anything to our understanding of nature.

Answer 4

If I understand your question correctly, you are asking what light would be at rest, rather than galloping along at 669,600,000 miles an hour?

Light is pure energy which is interchagable with mass. In theory, it would be converted into a small quantity of mass. It would not be "massless" at rest.

Answer 5

Photons do not have mass no matter how fast they're going.