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Glow sticks, star stickers, heavy metal posters, and all other glow-in-the-dark novelties are powered by phosphors, chemical compounds that emit visible light after being radiated. As this nifty downloadable PDF file from the Energy Information Administration points out, phosphorescent materials continue to glow after their energy source (light) is gone, while fluorescent materials will dim immediately. The electrons in phosphors, like children and politicians, are easily excited. When charged with light, they quickly ascend to a higher electron orbit, giving
off light energy in the process. Glow-in-the-dark light emanates from electrons that are in an intermediate but still excitable condition, kind of like the way you feel after you've just finished the hundred-yard dash. The knowledgeable staff at How Stuff Works notes that most glow-in-the-dark toys contain either zinc sulfide or strontium aluminate, because these substances have relatively long phosphor persistence (i.e., they glow longer). Some pricey watches contain glow-in-the-dark elements that don't need charging, because they contain mildly radioactive materials. Guess what? You're staring at a group of densely clustered, electrically charged phosphors right now. TV sets and computer monitors use thousands of tiny phosphor elements to emit varying shades of red, green, and blue.
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