One of our erstwhile Angrymen has challenged the techno-savy to come up with the design for a lightsaber. Being a somewhat techno-savy sort, I gave it some consideration.

The lightsaber is the weapon of the Jedi Knights and their battle against the Dark Side of the Force.

The lightsaber, according to the the Star Wars Databank, is a weapon with a handle which emits a beam of light, which can be used to deflect blaster (assumed energy) bolts, bullets, and when used properly, fence froissment and attaque au fer with the enemy Sith Lords. That last phrase essentially means that a beam of light can approach solidity when acting against another beam of light. Well—actually no.

The naive might conclude that, provided a powerful enough energy supply (located in the handle), that this might be possible, but light is composed of photons, which are bosons and behave with Einstein-Bose statistics. That is to say that you can stack as many of them as you want into as small of a space as you wish and everything is ok. Unfortunately, the Sith Lord’s lightsaber is also a bag of bosons and also has no problem stacking itself into the same space that your bag of bosons occupies. As a result of basic particle statistics, one lightsaber will always pass through another. So there goes the fancy fencing. Also, I am obligated to point out that energy blasters are also likely photons which obey Bose Einstein statistics. So no deflecting energy bolts either. Projectile weapons fare better.

Matter is composed of electrons and photons (and pesky little neutrons) which are fermions, i.e., they obey Fermi-Dirac statistics and as a consequence, no two of them can occupy the same energy state. Because of this matter has solidity and rigidity. Now a particle (bullet) careening toward your basic Jedi Knight, can be deflected by the lightsaber beam because the glob of fermions will have some coupling with the photons. The coupling is on the order of 1/137 so you need a really powerful beam of photons to create the scattering (most likely reverse Compton scattering), but at least it’s feasible. So Hollywood and George Lucas got it wrong (no suprise there).

Sorry, Angry Immigrant, can’t be done that way.