What common beverage glows in the dark?
Tonic water can glow in the dark. Tonic water is best known for adding a little bite to cocktails, though it has a hidden talent: It glows when exposed to ultraviolet light. While modern tonic waters often include citrus flavors or sweeteners to ease their bitter taste, the mix is traditionally crafted from just two ingredients — carbonated water and quinine, the second of which is capable of illumination. Quinine’s ability to glow, technically called fluorescence, occurs only when the substance is exposed to the right conditions, particularly when its molecules absorb invisible ultraviolet light (such as that projected by a black light). The excited molecules then quickly release that energy, which appears as a blue hue to the human eye in a darkened room.