The famous light sabers of the epic Star Wars saga have captured fans imagination ever since Obi Wan first revealed this ‘elegant weapon for a more civilised age’.
Pretend light sabers have been available, but are there credible physics principles behind this device that could allow us one day to build a real one?
To answer this, consider many issues you must…
- The energy source required to, for example, melt your way through a metal blast door, would be huge! You'd need a small, intense source of power, that could be carried in the hilt of the saber. Current conventional batteries have far too little energy density.
- A simple laser beam generated from a portable hilt is not a light saber, it's a scary laser pointer! A laser with sufficient power would cut (and pose a major health and safety hazard!), but the blade would not stop after a metre or so. Unlike the finite blades carried by respectable Jedi, it would continue until it meets a distant object (or is scattered). A reflecting mirror on a telescopic support could be included, though you then couldn't use the light saber end to stab effectively at the dark side.
- We know from Maxwell's equations of electromagnetism and from particle physics theory that light particles (photons) at visible frequencies essentially do not interact with each other, so two blades made of simple laser beams would not clash. It might be best to use a plasma, in which the force in the clash of two blades could be generated by the electrostatic repulsion of charged ions in the plasmas. You'd then, however, have the problems of containing, controlling and wielding a super-heated plasma!
Some really impressive suggestions to design a light saber are given in this video by Michio Kaku, which is based on a superheated air plasma, blown at high speed into a heat resistant ceramic telescopic tube, using a futuristic "nanotube" battery as a power source:
It seems that our best chance of creating a light saber is to use a stream of particles, such as a plasma. In the department of physics at Royal Holloway, and within the John Adams Institute, we use "laserwires" to measure the size of energetic particle beams at CERN and other accelerators in the world, and we even have started some innovative research involving Laser-Plasma beam acceleration. More info here.
For now then, our light saber fights must continue using only invisible ones (with added mouth-generated sound effects of course) while I pursue my exciting (and peaceful!) research involving lasers and high-energy accelerators.
May the force be with you!