FORCE FIELD

   In sf TERMINOLOGY - unlike physics, where it has a different meaning - a force field (sometimes a force shield) is usually an invisible protective sphere or wall of force. Throughout the 1930s and 1940s the force field performed sterling service, notably in E.E. "Doc" SMITH's Skylark and Lensmen series, where force fields under attack glow red and orange andthen all the way up through the spectrum until they reach violet and black and break down. Force fields are also a sovereign remedy against DEATH RAYS and usually bullets, too, though not against swords in Charles L.HARNESS's Flight into Yesterday (1953; vt The Paradox Men dos), in which the efficacy of the shield is directly proportional to the momentum of the object it resists; this property of force fields gives Harness a good excuse to introduce swordplay (where the momentums are relatively small) into a technologically advanced society - an example that other writers were not slow to follow. Robert SHECKLEY's "Early Model" (1956) tells of a force field so efficient that it renders its wearer almost incapable of carrying out any action at all that might conceivably endanger him. The eponymous device in Poul ANDERSON's Shield (1963) can recharge its batteries by soaking up the kinetic energy of the bullets it stops. But these are comparatively late examples, when the concept was sufficiently familiar in sf to allow parody and sophisticated variations.It is the essence of an sf force field that by a kind of judo it converts the energy of an attacking force and repels it back on itself. Few writers, however, were able to give - or concerned to try to give - a convincing rationale for forces being conveniently able to curve themselves around an object and to take on some of the properties of hard, resistant matter. A well ground mirror might more plausibly carry out the same function, at least against death rays. The true rationale for the force field and for its close relations, the tractor beam (which pulls objects towards the beamer) and the pressor beam (which pushes them away), is that - like FASTER THAN LIGHT travel - they help tell stories.

   PN