Tuesday, December 02, 2008

Light Sabers and fluorescent tubes

Watching the repeats of the original Star Wars trilogy on television recently, I was struck by a couple of things. Firstly, the woeful CGI scenes added by Lucasfilm in the 1990s, stand out like a gangrenous thumb. Not only do they fail to add anything to the orginal cut, they detract significantly from it. It is as if Leonardo da Vinci has been given the opportunity to revisit the Mona Lisa, and has chosen to spray-paint a couple of ears on her.

One particular piece of CGI, featuring a Landspeeder driving into Mos Eisley, is so poor that it would be castigated were it to appear in a PlayStation game; it's out of scale, out of perspective, has no variation in focus, and has an ersatz quality of light and colour.
The second thing I noticed is that the Light Sabres (note the spelling) produce light in a manner which resembles neon lighting, or fluorescent tubes. Sure enough, it seems that when Nelson Shin designed the Light Sabre, he reasoned that since the Light Sabre is made of light, it should look 'a little shaky', just like a fluorescent tube.

As explained with exemplary clarity by Dr Chris Smith, neon lights and fluorescent lights generate visible light by distinct mechanisms. In a neon light (or lights using other noble gases, such as argon, krypton or xenon), the tube is filled with a gas that simply emits visible light when stimulated with an electrical current, and the tube itself is transparent to the passage of this light.

In contrast, in a fluorescent tube, the visible light is generated by the interaction of two distinct light-generating processes. The tube in such a light is filled with a gas, in which luminescence is once again stimulated by an electrical current. In the case of a fluorescent light tube, the flow of free electrons excites bound electrons in a gas of mercury atoms, which then emit ultraviolet light when the excited electrons return to their initial energy levels. The light emitted by the gas in the tube is then absorbed by a fluorescent material, called a phosphor, which is deposited on the inner surface of the tube. This raises the energy levels of electrons in the phosphor, which then emit visible light when those electrons return to their former state. The colour of the light emitted by the phosphor depends upon the precise blend of metallic and rare-earth salts used.

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