energy and mass are same by E=mc^2
No.it does not have.One basic reason is gauge invariance.
two photons can create particle antiparticle pair.They have energy which is converted to mass.
You may have written you need energy to create mass or vice versa.
Every photon has energy,momentum,spin.Energy is simply E=h-ω
is a photon a force . like gravity, magnetic fields etc. are forces create by mass ?????
mass of electron in natural units is 0.511 Mev.Only if you use the concept of relativistic mass, which is done in ancient textbooks and bad TV documentations only.
if you don't use the definition of relativistic mass then,right.Otherwise both are same.Energy is time component of four momentum and mass is invariant,so they are really different. if one avoids the notion of relativistic mass which is already abandoned then of course it is wrong.But that is just not what I say.It is a matter of definition.You are missing the point. E=mc² is wrong. The correct formula is E² = p²c² + (mc²)²
Oh,sorry for that.Fact that use of m as symbol for relativistic mass is outdated was the whole point of mfd's comment, and the reason for your reply to denisfl8 being at very least incomplete.
Mass, without qualifier, is assumed to be invariant mass. If you want to talk about relativistic mass, you should qualify that for clarity. Were you to reply that, "Energy is equivalent to relativistic mass," there would be no complaint.