Like how can any particle have no mass? Other particles like protons and electrons have mass, what’s so special about photons then?
In: Physics
It’s best not to think of particles as having mass or not having mass. E=mc^2 isn’t just saying that energy and mass are equivalent, it’s saying that mass is just a flavor of energy.
Some particles have mass, some don’t. They all have momentum.
E^2 = (pc)^2 + (mc^2 )^2 is the equation for relativistic energy-momentum. As mass, *m*, goes to zero for particles like the photon, it’s total energy is defined entirely by the momentum, *p*.
Mass dominates the total energy in nearly all trivial situations of massive bodies, driving the over-valuation of a particles mass to the casual observers. Understood, this equation shows the significance that momentum – obviously dominant in massless particle – can have. So it becomes not all that strange that some particles are massless, as they all have energy in varying forms.
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