Physics Question #30

Anonymous, a 15 year old male from the Internet asks on July 13, 1999,

How can I create a real light saber? It does not have to be completely like the ones in the movie but it must be in a sword shape, able to stop another light saber, self-terminating, and able to cut through anything but another saber.

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The answer

Barry Shell answered on July 13, 1999

C'est une des questions les plus populaires chez Vous ne pouvez pas créer un sabre laser qui fonctionne qui coupe vraiment des choses. Mais vous pouvez créer un sabre laser accessoire semblable à la sorte utilisée dans les films de Stars Wars. Essayer une recherche de google des répliques de sabre lasers pour les détails au sujet de comment les acheter ou les faire.

Un sabre laser "réel" est complètement imaginaire et n'a aucune base en réalité. D'une part, il n'y a aucune voie physique (autant que je sais) que la lumière peut arrêter la lumière. Même les lasers les plus puissants vont juste directement l'un par l'autre. C'est une caractéristique de la physique de lumière. En d'autres mots, les sabre lasers ne pourraient jamais s'affronter. Deuxièmement, si c'était vraiment une bielle claire, qu'est-ce qui le fait s'arrêter à environ un mètre de longueur ? Un miroir ? Qu'est-ce qui tient le miroir là-bas ? Je ne peux pas imaginer une méthode physique de le faire, à moins que nous ne parlions l'antigravité, qui est un autre concept imaginaire. Les sabre lasers sont une bonne idée, comme les machines de temps et les hyperdrives sont des bonnes idées, mais en réalité, ces choses sont complètement imaginaires et n'ont aucune base dans le fait de jour ou la physique.

James Fernandez, Inventor and mechanical designer in Henderson, Kentucky answered on March 31, 2009

Who says it is made of light? In the sci-fi terms that define what a lightsaber is constructed of, it wouldn't work. But even George Lucas himself admitted that he was simply creating fiction and didn't know anything about how it would work. He just called it a lightsaber emits light. When you go home and say "turn on the light, would ya?" are you referring to a nonstop beam of light? No, you're visually describing an incandescent bulb operated by electricity, which of course emits light. Same thing applies to a lightsaber - it emits light, but that doesn't mean it is made of light. When little Anakin told Qui Gon that he saw his laser sword, are you going to accept that as fact? Anakin was a kid when he said that, and had no knowledge of how a lightsaber was constructed, nor physics for that matter. You're gonna go off the word of a KID?

If you want to build a lightsaber, you have no choice but to go with existing technology, and if it doesn't exist, well then - invent it. A plasma saber can be called a lightsaber because it would emit light. Plasma is possible here people. It occurs naturally everyday. Physicists always yammer about how you can't generate enough power to inject a plasma into a magnetic field, which bugs me because they're always talking about plasma and magnetic fields as if one has absolutely nothing to do with the other - like they should be regarded as two separate and unlinked entities. Let's talk electricity. A flow of charge generates an electromagnetic field, and vice-versa an EM field will generate a flow of charge. Now let's talk about conductivity. Your best conductors are silver and copper. These are good conductors. Some materials oppose a flow of charge - these are known as nonconductors. But, as fate would have it, nonconductors will conduct just fine if they become ionized. Fo r example, a simple capacitor utilizes this concept. A charge builds up one one end of the capacitor, seeking to dump to the other end to complete its circuit. To accomplish this task, a nonconductor is sandwiched in between. And that's when something amazing happens. When enough charge builds up, the nonconductor becomes ionized and the capacitor is able to make its charge dump. When this occurs, the nonconductive material returns to its nonconductive state and the process starts all over again.

Of course, you're thinking, how does this answer my question? We live on a giant capacitor. The clouds in the sky will gradually build up a static charge. And naturally, when enough charge builds up, you get lightning. Air is a nonconductive material until it becomes ionized. And when a material becomes ionized, this means that each atom has enough energy to excite its electrons to another level until one gets bumped off. What results is a flow of charge, a flow of electrons, charge in motion - a current, pushed by a massive voltage. This of course leads me right into plasma. What IS plasma? Plasma is simply an ionized gas. It doesn't matter what type of gas it is, as long as it IS a gas. Air is a gas, and when it becomes ionized, it is converted to plasma - this is what we call lightning. And, of course, I'll say it again - any charge in motion generates an EM field, and therefore plasmas generate their own EM fields. This is all I will say for now - that lightning (electron arcing) is the simplest way to create a plasma saber. Of course, lightning zigzags, because it follows a nonlinear path of the least resistive molecules in the air. If you use a laser in tandem to heat the molecules, this will provide a linear path of least resistance. And PLEASE remember that like polarities will always repel. If you keep it simple, simple solutions will always present themselves. 

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