Why do glow-in-the-dark things light up when it’s dark? – Haygarth, 5, United Kingdom
melissamayerDear Haygarth,
I love glow-in-the-dark stickers. I leave them next to a sunny window for a little while. Then turn off the lights and watch them glow.
I asked my friend Hergen Eilers how those stickers work. He’s a physicist at Washington State University.
He told me that glow-in-the-dark things use a type of phosphorescence. That means they absorb energy—like light—and then glow. A material that can do that is called a phosphor.
Glowing in the dark works because of electrons.
Everything in the universe is made of atoms. That includes you, me, whatever you’re reading this note on—and glow-in-the-dark stickers.
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