For hundreds of years, sci-fi writers have imagined weapons that might use energy waves or pulses to knock out, knock down, or otherwise disable enemies--without necessarily killing them. And for a good 40 years the U.S. military has quietly been pursuing weapons of this sort. Police, too, are keenly interested. Much of this work is still secret. Scientists, aided by government research on the bioeffects" of beamed energy, are searching the electromagnetic and sonic spectrums for wavelengths that can affect human behavior. Recent advancements in miniaturized electronics, power generation, and beam aiming may finally have put such pulse and beam weapons on the cusp of practicality. Weapons already exist that use lasers, which can temporarily or permanently blind enemy soldiers. So-called acoustic or sonic weapons ... can vibrate the insides of humans to stun them, nauseate them, or even "liquefy their bowels and reduce them to quivering diarrheic messes," according to a Pentagon briefing. Other, stranger effects also have been explored, such as using electromagnetic waves to put human targets to sleep or to heat them up, on the microwave-oven principle. Scientists are also trying to make a sonic cannon that throws a shock wave with enough force to knock down a man. Years ago the world drafted conventions and treaties to attempt to set rules for the use of bullets and bombs in war.