All my life, I’ve been fascinated with things that glow in the dark. Where does the light come from? This is now fundamental to my understanding of prayer, and of my vocation. The picture shows what I take for the latest advance in the world of fluorescent materials. Here are germanium nanoparticles in a colorless colloidal (gelatinous) suspension, being irradiated by ultraviolet light. By virtue merely of where they are and what they are, the invisible light that shines