If you believe what they portray in the movies, armies of the future will replace bullet-based guns with ray guns like the phasers used by the crew of the Starship Enterprise in "Star Trek." The United States military has announced that it is developing a new technology that closely resembles those futuristic weapons. This new directed-energy beam weapon exploits one of our natural defense mechanisms -- pain.

Anytime we get hurt, we feel pain, and our first response is to move away from the source of that pain. For instance, if you touch a hot light bulb, it burns your skin. Your body recognizes the pain and causes you to jerk your hand away from the light bulb. This natural reaction is the basis for the U.S. military's new pain beam, which burns the surface of the skin in order to drive away adversaries. Officials say that the "non-lethal" weapon, called active-denial technology, doesn't cause lasting damage to the people hit by it.

This new pain beam is an alternative to conventional weapons that are designed to injure and kill. One official said that the weapon is particularly useful when innocent persons are mixed in with adversaries. In this edition of How Stuff Will Work, you will learn how the beam weapon heats the skin and what research will have to be done before it is field-ready.