Lord Wilmore is absolutely right. The best guess at the moment is that prehistoric, possibly microbial life inhabited the terrestrial areas which harboured the Sun and the Moon. When the photoelectric effect turned them into massice discs and sent them hovering into the sky, they took their microbes with them. The microbes evolved two types of bioluminescence, both probably defense mechanisms against predation. The Solar microbes emitted hot light, which is today exploited by plants, but which also has cancerous effects and can temporarily blind predators, and the Lunites emitted cold light, which is more injurious to modern plants and animals, and can cause more permenant blindness and other ill effects. The Antimoon either lacks microbial life entirely, or its inhabitants never developed bioluminescence.