Why is glass transparent?

Sixty Symbols regular Professor Phil Moriarty discusses transparent glass and the so-called energy gap. PS MESSAGE FROM PROF MORIARTY: “I misspoke for the last sentence of the video. What I meant to say is that the photons don’t have enough energy to excite electrons across the energy gap and therefore light is transmitted. What I said was precisely the opposite, contradicting everything else in the video. Apologies for any confusion caused.“ More physics at