Since Heaven is a spiritual plane, there may not be the referents as here in the material one. For instance, there may be no darkness since the glory of God might illumunate everywhere in Heaven.
I understand now:
Rev.21:23 And the city had no need of the sun, neither of the moon, to shine in it: for the glory of God did lighten it, and the Lamb is the light thereof.
The same light as Gen. 1:3-4 ???
And God said, "Let there be light:" and there was light. And God saw the light, that it was good: and God divided the light from the darkness
.......Ping