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http://science.howstuffworks.com/light-stick.htm
Since their invention 25 years ago, light sticks have become a Halloween staple. They're perfect as safety lights because they're portable, cheap and they emit a ghostly glow. Light sticks are also extremely popular on the rave scene (as are light necklaces, light glasses and light rope), and they make an ideal lamp for SCUBA divers and campers.