A tractor beam is a device which can manipulate objects from a distance; the concept is primarily theoretical, rather than actual, so it is difficult to define how, exactly, a tractor beam works. Many science fiction films and books feature some variant of the tractor beam, often utilizing a high-powered laser. Typically, a tractor beam attracts objects, pulling them closer to the source of the beam, or it is capable of locking onto a target in order to move it. In contrast, a pressor beam repels objects, forcing them further away.
Although most people think of tractor beams as the stuff of science fiction, they actually do exist, but only on a molecular level. Scientists in the early 21st century were able to develop so-called “molecular tweezers” which could manipulate molecules without actually touching them, using very precise lasers. While these miniaturized tractor beams might not seem as exciting as the stuff of Star Trek, they represented a major breakthrough for the scientific community.
In the realm of science fiction, a tractor beam can be used for a variety of purposes. In many instances, the beam is used to move objects such as cargo and small space ships, along with people. In some instances, the tractor beam of a larger space ship acts as a docking device for smaller ships, locking onto them and bringing them safely up alongside the larger ship. These beams can also stabilize approaching craft or manipulate objects on board a spaceship. In some instances, tractor beams are powerful enough to lock ships into place for towing.
Of course, the tractor beam is also turned to good use in scenes with criminals. For example, the beam could capture an escaping criminal ship, or lock criminals in place until law enforcement can reach them. Criminals in turn use various shields and pressor beams in an attempt to evade capture. However, in sci-fi, the good guys usually win eventually, so these measures tend to fail in the end.
Like many things in science fiction, there is an element of truth to the idea of a tractor beam, although scientists have been unable to create large-scale tractor beams as routinely depicted in science fiction. However, it is possible that we may one day see giant tractor beams in active use, along with other delightful fantasies of science fiction, from alien races to flying cars.