Introduction
A lightsaber is an iconic fictional weapon from the movie series Star Wars, and is described to be able to cut through most substances. Physicist and futurist Michio Kaku actually made a descriptive idea of how to make a lightsaber in his book Physics of Impossible.
Blade
A lightsaber’s blade has mainly two properties. One, it is hot enough to cut through almost anything, and two, it has to clash with another weapon. Although lightsabers are sometimes called “laser swords”, lasers do not do a good job mimicking these properties. Lasers are concentrated beams of light. Light is made up of photons, which are bosons, a type of subatomic “particle” that is massless and can overlap each other. Which means anything that touches them will simply slip through. Hence they will not clash, and are difficult to stop midair like a sword.
Plasma is proposed instead. Plasma is often called the fourth state of matter. In a plasma, the atom consisting of mass has so much energy that it breaks apart into subatomic particles. So plasma from some elements can have very high temperatures. Conveniently, lightsabers are considered plasma swords in the current star wars canon. There are already plasma torches used for dissecting hard material. The best thing about plasma is that it can be controlled by magnetism. Plasma consists of subatomic particles like electrons and protons, each having a negative and positive charge. So a strong magnetic field can shape the plasma into a blade-like shape.
Still the blade will not clash because plasma has extremely low density. Plus, it is hard to create a magnetic field strong enough to contain it in a blade shape. So a solid blade “core” that sets the magnetic field will be needed. This core object has to be solid, but can withstand extreme heat of the plasma blade. One such object is high temperature ceramics. Substance also used for protecting spacecraft from the heat caused when reentering earth’s atmosphere.
Energy Source
An incredible amount of energy is needed to sustain a superhot plasma blade. In order to contain such high amounts of energy in a hand held hilt, a normal chemical battery is not enough. Instead, it is hoped that carbon nanotubes could do the job. Carbon nanotubes are sheets of carbon that are about an atom thick. One property that carbon has is that it conducts electricity extremely well. This can make normal chemical batteries perform better, but on their own they can make excellent power storage. This type of power storages are called capacitors, and they store energy in electric fields rather than as chemical energy. Although a stable production of large amounts of CNTs are still something in the future, it is a very promising technology.
Problems
Although a lightsaber is probably not impossible to create, its practicality as a weapon is still questionable.
One problem is if the heat of a lightsaber touches any sort of flesh, it will cause a phreatic explosion. Basically, the water inside animal bodies will rapidly evaporate and expand when in contact with a lightsaber. Because animal flesh consists mostly of water it will cause an explosion, and it will be quite a large one .
Another problem is that the heat emitted by a lightsaber will be extremely high, even with some distance. So the safety of the user can not be assured.
Sources
[1] Kaku, Michio (2006). Physics of the Impossible: a Scientific Tour beyond Science Fiction, Fantasy and Magic. Last accessed: 30 June 2017
[2] “How Close Are We to Creating a Lightsaber?”. Seeker. https://www.youtube.com/watch?v=dK2ym66or6E&t=435s. Last accessed: 5 June 2020
[3] “Michio Kaku – Can you build a real Lightsaber ?”. https://www.youtube.com/watch?v=1lr5OUjFDkg&t=923s. Last accessed: 5 June 2020
[4] Hill, Kyle and Bowser Andrew (2017). “Why Death by Lightsaber Would Be Much Worse in Real Life! (Because Science w/ Kyle Hill)”. https://www.youtube.com/watch?v=BRAyIXgWBWc Last accessed 5 June 2020
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