Well of course I knew there was a sun because of the sunlight on those places, I was just confused because the space view of the UDD didn't show it, as Floridan Citrus explained. Also speaking of light, how were the cycles of night and day maintained within the MU? Did Mata Nui have to manually control the amount of light at day and at night, or was there a built in lighting system that dims the light at night or something like that?