I've done something similar in my Zero Gravity game (long time iOS project), where I had astronauts engaged in rag roll kung fu in space, with a GLSL earth in the background with day/night cycles. Just like Star Wars has sound in space, my game (as well as the linked renderer) added ambiant light to see the unlit part of earth. However, there is no ambiant light on the dark side of the moon<-<-<- earth.