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What makes glow-in-the-dark stuff glow?

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What makes glow-in-the-dark stuff glow?

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Q: In the old days radium was used to make watch dials that would glow. Today we have a million things from the plastic stars on my daughter’s ceiling to the watch on my wrist that will give off light long after they are exposed to light. What material now makes all these things glow? [© 1997 Charles Hoberman, used by permission] The glow-in-the-dark Hoberman Mini Sphere. A: The material is called phosphor. It has atoms with a peculiar property: Shine visible light on a phosphor and you excite the electrons in its atoms so they jump to a higher energy state. They have enormous difficulty radiating energy as light. So the excited electrons stay there at the higher state­stuck–for as long as several hours. If you quit exciting the electrons by turning off the light, then the electrons eventually return to their original state by emitting light. They glow in the dark. Toy makers commonly use two phosphors: Zinc Sulfide and a newer one that glows much longer, Strontium Aluminate. Further

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