We all recall the first time we saw a lightsaber deployed in a Star Wars movie, because they were just so cool. But can anything like this technology ever come to exist, or is it just magical? Gizmodo asked two physicists and a photonics professor about the possibility. Dennis K. Killinger of the University of South Florida explains how such a laser weapon wouldn't work as it does in the movies.
The one aspect of lightsabers that seems infeasible is the concept of its acting as a solid physical rod or saber that can “hit” or “strike” an opponent. In the movies the mechanical hitting of the dueling lightsabers is enforced by sound effects—the lightsabers have a “hum,” and you can hear them hitting each other. But if you take two flashlight beams and cross one beam with the other beam, there is no sound or force experienced by one light beam on the other. This is because photons have no mass, which means that a laser or optical beam has no mass. To get the point across: I like to say that “You can’t use a light beam to hammer a nail.” So in this sense, it is not feasible that two laser beams can “hit” each other in the mechanical sense. However, there is a scientific exception to this: as discovered by recent physics Nobel Prize winner A. Ashkin, a laser beam under the right conditions can be used as an optical trap or as an optical tweezer to trap and move very small objects, such as a bacteria. While one could stretch the truth and call this a Star Wars Tractor Beam, there is a 1,000 billion billion times difference between moving a bacteria and the mass of a starship (ie. SpaceX second stage starship.)
However, the experts agree that if "lightsaber" is a misnomer and the actual weapon is made of plasma particles, that opens up all kinds of possibilities, none of them yet feasible. Read what they all have to say at Gizmodo.