How can photon have energy, but no mass if “m=E/c^2” (E= mc^2)

Question

How can photon have energy, but no mass if “m=E/c^2” (E= mc^2)

In: 42

Answer 1

Because E=mc^2 isn’t the full equation.

The fuil equation is E^(2)=(mc^(2))^2 + (pc)^2 where *m* is mass and *p* is momentum. When momentum is zero (or near zero) then the mass portion is dominant because it is squared again (note that it is **E^(2)=** and not **E=**).

Photons have momentum even if they have no mass.