Light Sabers

Science Fiction: Fact and Fantasy Series

By Romana Annette  04/6/2008

According to Wikipedia, the light sabers made famous by Star Wars are the most popular of all cinematic weapons.  They purposely evoke a Samurai-like skill and mastery in science fiction and fantasy stories; those who wield such lethal weapons are often assigned mythic qualities of old. 

Supposedly, the color of the beam of a light saber represents a level of mastery in the Star Wars sagas.  Some characters, such as Darth Maul, even sported a double-ended light saber as a bratty display of their skill and prowess, though one wonders how anyone could live to master such a weapon before cutting themselves to pieces.  Civilized, maybe, but light sabers are not benign weapons, since they can mercilessly cut through metal and flesh alike.

No one currently knows how to build an actual light saber, and speculation about how the cinematic versions work leads to endless problems.  A light saber is likely a loop of concentrated energy, but the loop is so tight that it cannot be discerned.  Some have claimed that the loop is plasma, but plasma is a very hot, ionized gas, which would require a very powerful containment field.  Several times in Star Wars light sabers are also referred to as laser sabers and laser swords, but never as plasma sabers.

Light sabers are a class of devices that use bounded fields.  Other types of bounded fields found in science fiction are force fields and artificial gravity fields.  No one currently know how to build a bounded field, since all known fields extend to infinity.  In fact, in physics, fields have no presence, except because of the way particles of matter and energy react with them.

There are additional problems with using lasers as bounded energy weapons.  The photons of light have zero spin, compared to particles with mass that have spin in non –integral multiples of ½.  This concept of spin is not simply about rotational axes, but is about how particles of matter and energy interact, instead.  Particles of mass conform to what is called the Pauli Exclusion Principle, while particles of energy do not. This Principle simply says that no two particles of matter that have mass can be in the same physical state at the same time.  Thus, particles of matter will attempt to maintain their current state against any intrusion by other particles of matter, while particles of energy will not.

A beam of laser light will resist any containment, and two lasers will exhibit interference patterns if they cross, but they will not repel each other.  Clearly, in Star Wars, light saber beams chatter as they repel each other.  In this context, it is simply impossible to build a bounded laser that works like a fictional light saber.  Laser beams seek to extend to infinity, and they can never repel each other.

The only possible construction for a light saber would be a very tight force field that could completely contain a beam of laser light.  However, under quantum mechanical rules, there can be no field that can completely contain anything, since there would be a probability that some particles could pass through any barrier.

We have just managed to develop lasers, but no one is even close to developing a force field, especially a hand-held version.  Since we cannot build a force field, we cannot describe what would happen when two force fields touched each other.  It is probably safe to say that light sabers will be relegated to the realm of fantasy and science fiction for some time to come.

Sadly, we cannot look forward to any Jedi Knights coming to the rescue for the foreseeable future.  This is unfortunate, since we seem to be overrun by Sith Lords and their counterparts.