Lightsabers are composed of plasma and typically weigh just over 2 lbs (1kg), including the hilt. Hence, they are maneuverable weapons that work well in one-on-one duels. Yet, they are actually supposed to feel heavy even though they have low mass. Why do they feel heavy if the blade itself has no mass? That’s what Lucas had in mind, and that concept returned with the Darksaber.
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Lightsabers Can Be Heavy
As this Reddit exchange reveals, we may think that lightsabers would be light since they don’t have “any significant mass”. However, they do “feel heavy” because “the blade exerts force when active.” One way to think of it is by making a comparison to “a constantly firing rocket motor” where the heaviness arises from “the imbalanced ‘thrust’ of the constant energy stream.”
This discussion and explanation derive from Mark Hamill’s and George Lucas’s comments about why lightsabers should be heavy. Recapped here, Lucas and Hamill discussed in “old interviews” that lightsabers were meant “to be as heavy as real swords” and usually needed “two hands to hold.”
In 2014, as the above article and Reddit board discuss, Hamill went into it further and specified how Lucas had “imagined lightsabers to weigh between 40 and 50 pounds.” Holding a lightsaber was supposed to be equivalent to using “the mythological sword Excalibur.” Lucas stressed this idea when filming A New Hope and The Empire Strikes Back.
This short video has Hamill and Lucas expressing these ideas and adding how the blades were “very powerful” and had “a lot of energy.” So, the energy basis is where the weight comes from, at least in Star Wars. The constantly firing rocket motor comparison provides a good visualization of the idea of how energy could make something feel heavy.
Yet, according to rocket principles, this example does not quite account for the perceived mass. That is, the rocket parts make up the mass, especially the propellants or fuel, which actually dissipate as the rocket burns. So, the mass would decrease too.
In our fictional universe, though, the lightsabers were initially meant to feel heavy, even if skilled with the Force.
It Depends on the User
However, we saw that the heavy factor changed by Return of the Jedi, and even before with Vader in Empire Strikes Back. Some of the above sources talk about this transition and how Lucas relaxed on the heaviness by the third original movie.
This adjustment provided a way for better fight scenes, but also made it look like those who were more skilled with the Force would wield their blade better. In this collection of duels, we can see Luke’s skill progress while battling Vader (while still using two hands) and even more advanced fighting with Qui-Gon, Kenobi, and Maul.
However, with Rebels, we started to see a reversal of this lighter-weight lightsaber. As Sabine Wren trained with the Darksaber, she talked about how heavy it felt. Kanan explained how she was “directing a current of power” or flowing energy that made it feel that way. This video includes this scene while comparing it to the struggles Din Djarin had with this same lightsaber.
To some extent, we came full circle back to the heaviness of the lightsaber, even though the blade has no mass.
Lightsabers and Mass
Originally, lightsabers were supposed to be heavy because of Lucas’s vision for them. The energy basis made them difficult to wield. As we progressed into the third film, we saw some relaxation of this weight issue that coincided with more skilled users being able to fight with them better. With recent shows, the heaviness of the blade returned, at least for the Darksaber.