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# What does it mean?

Photons don t have rest mass but they do have energy and hence mass.I don t know , I picked up this statement from somewhere and I was like whatttt? So please answer this question?

### 2 Answers

- dawgdaysLv 74 years agoFavorite Answer
No, photons do not have mass.

The equation E = mc^2 relates energy and mass, in that energy and mass can be converted, one to the other. What it does NOT say is that a photon (which is energy) also has mass.

But that equation is actually a short form. The full equation is

E^2 = m^2*c^4 + p^2*c^2

Where p is momentum. So while a photon has zero mass, it's energy has a momentum equivalent.

- D gLv 74 years ago
Photons have 0 rest mass

Rest mass is mass of object when at rest

Since photons always move at light speed they cannot exist at 0 m per second

If you look at relativity equations for mass the photon moving at c can have mass