This evening I saw the 4th July classic Fireworks in San Diego, and I was wondering about the most physical picture of what was happening. Does anyone have a good way to explain the detailed physical features of the phenomenon?
It's "just" plasma physics. The "fire" part heats up atoms to the point where they lose electrons. When those ions regain electrons, the electron undergoes transition in energy state from free to bound. This energy is released as a photon (since electrons are bound electromagnetically to atoms). The energy of the photon is tied to the electrical energies of the bound electron state, which in turn is determined by the number of protons in the nucleus.