Star Wars: How Hot Is A Lightsaber?
It's all fun and games until someone powers up a lightsaber and every living thing within several hundred feet spontaneously combusts. Now, that might not be what George Lucas had in mind when he created his iconic fantasy weapon, but it's what would happen if lightsabers were a little more true to life.
While the science behind lightsabers is heavily contested, according to Brandon Weigel, a self-proclaimed astrophysics and engineering enthusiast who based his calculations on the scene in "Star Wars: Episode VIII – The Last Jedi" in which Rey Skywalker (Daisy Ridley) decapitates a pillar of stone, lightsabers would need to burn at 20,566 Kelvin — or about 37,000 degrees Fahrenheit — to slice so easily through solid matter the way that they do.
To better frame his findings, Weigel compares kyber crystals, the energy source housed within every lightsaber, to nuclear power plants. "[Lightsabers] flare at a temperature hotter than the surfaces of most of the stars in our universe," he claims in a 2020 article he published on Medium. "To keep the lightsaber ignited for a mere 20[-]minute duel, the kyber crystal within the lightsaber's hilt would have to yield an energy density ... akin to the volume energy density of a plutonium fission reactor!" He then remarks that similar outputs typically yield purple light, meaning that Mace Windu's (Samuel L. Jackson) purple lightsaber is the only semi-realistic weapon in the bunch.
Fantasy science protects Jedi from catching fire
As Brandon Weigel notes, such extreme temperatures would mean that any biological matter within 350 feet would immediately burst into flames whenever a lightsaber is powered up, so there must be some fantasy science behind Jedi and Sith's ability to keep their flesh privileges while dueling. Weigel proposes that lightsabers use energy gates to contain the superheated plasma and most of the radiation until such time as the blade makes direct contact with physical matter. In layman's terms, his theory explains why lightsabers are only dangerous when the blade is touched and then only to whatever it's touching.
Of course, it's hard to apply real-world science about fire prevention to a franchise in which Obi-Wan Kenobi (Ewan McGregor) and Anakin Skywalker (Hayden Christensen) duke it out while basking in the usually unsurvivable glow of lava ... so it's all relative. However, Weigel points out that the energy gates would also allow for color customization, with the wielder potentially able to change their lightsaber's color simply by restricting or loosening the amount of radiation allowed through. What's a little extra radiation if it means getting to wield a pretty blue plasma sword, right?