system
Given the following post, respond as if you're commenting on Reddit:
human
If E=MC^2 and M(photon) = 0 then how does light contain/transmit [E]nergy? 

From what I understand, light travels at C because it has no mass. Anything with mass >0 cannot attain a speed of C. How, or why, then does light carry energy? 

I also feel correct in thinking that light (gamma radiation specifically) is indeed   the medium through which fusion of lighter elements (e.g. hydrogen into helium) loses mass in the process and gives off energy. 

But something without mass can have no energy[?] 

What am I missing? Some sort of quantum physics aspect? Does the very fact of moving through space at C endow an object with energy?--the energy of 1 photon? Do photons vary energy-wise or can "photon" be considered a unit of energy?
gpt
The energy equation you're looking at is incomplete, as it is the energy for a particle at rest. When moving, there is an energy associated with the momentum, p:

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

At rest (p=0) this reduces to E = m c^2 for a massive particle. For a photon, which always travels at v = c, the momentum is given by p = h(freq/c) = h/wavelength, where h is the Planck constant. Therefore:

E = pc = h freq = hc/wavelength.

So photons can have a different energy depending on the wavelength. For example, an X-ray (or gamma photon) with a wavelength of 0.1 nanometers has an energy equal to about 12400 eV. A photon with half that wavelength 0.05 nanometers, has energy 24.8 keV.