When you think<\/span> of Star Wars, you think of lightsabers. Right? What could be better, from a movie-making standpoint, than a futuristic sword that lets you create awesome fencing duels like in old-time Errol Flynn swashbucklers. (So much better than watching Stormtroopers fire their blasters into walls and ceilings and anything else except their targets.)<\/p>\n Lightsabers come in a cosmic rainbow of hues (color-coded blue or green for good guys, red for bad) and a variety of shapes. There\u2019s even a double-bladed version in Phantom Menace<\/em>. (I don\u2019t want to start a nerd fight\u2014yet\u2014but the best lightsaber battle in the canon has to be the \u201cDuel of the Fates\u201d in that movie, thanks to the skills and scariness of Darth Maul actor Ray Park.)<\/p>\n So \u2026 exactly what are<\/em> lightsabers? Of course, they aren\u2019t real, so nobody really knows how they work. Even the characters in the movies seem a little confused about it. In Phantom Menace<\/em>, Anakin calls it a \u201claser sword.\u201d Yeah, he was a kid, but both Din Djarin (the Mandalorian) and Luke Skywalker also refer to it as a laser sword\u2014though I suspect Luke was being sarcastic.<\/p>\n Anyway, that\u2019s just wrong: It can\u2019t be a laser. For starters, lasers beams are invisible from the side, so you wouldn\u2019t see a thing unless you staged the duels in a disco with fog machines to scatter the beams. Second, the beams go on forever; they don\u2019t have an end. Third, laser beams can\u2019t clank together like swords\u2014they\u2019d just pass through each other when you try to parry.<\/p>\n But what is it then? We can greatly narrow the possibilities by asking if the blade has mass. If it\u2019s some<\/em> kind of light (as you\u2019d think from the name \u201clightsaber\u201d), then the answer is no\u2014light, or electromagnetic radiation, has no mass. If we can determine that it has mass, then it\u2019s not light.<\/p>\n This is a question we can<\/em> answer, by analyzing how lightsabers move when you wave them around. In other words, it\u2019s time for some physics!<\/p>\n Don\u2019t confuse mass and weight. Mass is a measure of how much \u201cstuff\u201d like protons, neutrons, and electrons are in<\/em> an object, and weight is the amount of gravitational force acting on<\/em> an object. Here we want to see what impact the mass of a lightsaber would have on its motion. But let\u2019s start with something simpler.<\/p>\n Instead of a lightsaber, say we have a \u201clightball\u201d made of the same buzzy substance. Since it\u2019s symmetrical, we can describe its motion without worrying about rotation. If we want to move this ball back and forth, we call on Newton\u2019s second law of motion. This says the acceleration (a<\/strong>) of an object depends on its mass (m<\/strong>) and the amount of force (F<\/strong>) applied to it.<\/p>\nMass and Motion<\/h2>\n
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