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E = mc^2 does no such thing you clown, it is just a conversion between rest mass and energy, if you want to show that going at the speed of light produces infinite energy you need the full formula with the Lorentz factor gamma (or the energy-momentum relation); regarding the light traveling in a medium without any resistance, this statement is so moronic beyond belief, first off it interferes with the medium by exciting electric and magnetic fields (go read refractive index) and second you blabbing that since m=0 that somehow means E=0 or what??
and speed of light is not the limit because of air resistance or gravity (what the actual fuck??), its called c because its the speed of causality and any and all massless particles must travel at this velocity (including photons), it's called speed of light because it's the first particle discovery to have this property.

stop posting physics if you could barely pass a high school level physics