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.

While it may seem like supernatural magic, the technology behind light sticks is actually very simple. In this article, we'll look inside a light stick to find out how it gives off such a strong light with no bulb and no battery.

Light is a form of energy, which can be emitted through a variety of processes. These processes include:

  • Incandescence - The emission of light due to heat (as in an ordinary light bulb or a gas lantern)
  • Fluorescence and phosphorescence - The emission of light in response to radiation energy (as in a fluorescent light bulb or a television)
  • Laser generation - The concentrated emission of light using stimulated emission (see How Lasers Work for details).

All these processes work on the same basic principle: An outside source of energy excites atoms, causing them to release particles of light called photons. When you burn something, for example, heat energy causes the atoms that make up the material to speed up. When the atoms speed up, they collide with each other with greater force. If the atoms are excited enough, the collisions will transfer energy to some of the atom's electrons. When this happens, an electron will be temporarily boosted to a higher energy level (farther away from the atom's nucleus). When it eventually falls back down to its original level (closer to the nucleus), it releases some of its energy in the form of light photons. (See How Atoms Work and How Light Works for more information.)

A light stick does the same basic thing, but it uses a chemical reaction to excite the atoms in a material. We'll look at this reaction in the next section. ­