I think the original explanation was terrible. I also think that the explanation based on g* (E/c^2) makes no sense whatsoever. In effect, it encourages the people that claim that the photons have an equivalent mass m=E/c^2 which is totally wrong. Come to think of it, the whole page misses the fact that current experiments put a limit of 6*10^-17 eV on the photon mass (with newer experiments set to lower this limit). This limit is in total contradiction with any type of E/c^2 derivation. If you don't like my explanation of "photon in the box" could you please remove the entry altogether? It is very misleading and badly written as originally set. Thank you