SPOILER ALERT: Warning, this article contains spoilers from Star Wars: The Last Jedi. Proceed at your own risk.
Star Wars has always been a little light on the “sci” part of sci-fi. It uses its science references moreso as tools to tell its stories.
Sometimes it can be a bit hard to suspend disbelief when a glaringly inaccurate scene is unfolding before your eyes, but other times, Star Wars might be more in line with real physics than you think.
Here are a few scenes we saw play out in The Last Jedi with questionable physics — but some of them might surprise you.
The Binary Sunset
A meaningful and memorable moment from The Last Jedi is when Luke Skywalker looks upon the twin suns of Ahch-To. Earlier, Yoda had talked about how he has always looked to the horizon. After his strenuous projection to the battle of Crait, he looks to the horizon once more and sees twin suns very similar to the ones he grew up watching on Tatooine.
Binary star systems are actually a thing, and it was previously thought that they couldn’t sustain life. The volatile gravity caused by two stars could thrust a planet back and forth between extreme temperatures. But if the stars are far enough to minimally influence each other, or if they’re so close that planetary orbits are barely affected, it solves the problem.
Some computer simulations have suggested it might be just as likely for life to thrive in one of these as a single-star system. We know of 3,710 exoplanets currently, and at least 146 of them orbit binary star systems. Some of them have even more than two stars.
Usually these suns are much farther apart, but we have witnessed situations with closer stars that would lead to the kind of sunsets Luke Skywalker would look upon.
Leia the Space Wizard
So what happens to the human body when it’s exposed to the vacuum of space?
According to this NASA scientist, you wouldn’t explode or freeze or have your blood boil. You’d be conscious for ten seconds, and alive for about ninety. That consciousness wouldn’t be fully lucid, so you might have as few as five seconds to help yourself.
This actually happened once in a test accident. A NASA technician was decompressed to vacuum, stayed conscious for 12-15 seconds and was saved after 30 seconds. He was perfectly fine afterwards.
Leia didn’t display any of the symptoms of prolonged exposure to vacuum, such as swelling to twice her size, and she clearly didn’t stay unconscious.
Granted, the Force allows Star Wars to explain things away by saying “magic did it,” and usually I’d say that’s a weak justification. But there is some precedent here. Older force users are basically holding their body together until they “let go” and fade.
With the Expanded Universe axed, we don’t have the superpowerful Jedi Leia but she obviously still has the blood of Anakin Skywalker. The new wave of canon material hasn’t made it clear how familiar Leia is with her abilities, but it could be possible Leia held her body together in much the same way.
Things are Different in Space
The starships of Star Wars act as though they’re abiding by atmospheric physics.
To be fair, many sci-fi properties are guilty of this. It spans games, movies, comics and books. It’s just how we Earth-bound humans are used to seeing flight.
You can totally see why they do this, too. Realistic, Newtonian space battles are boring. You probably won’t even see the enemy ships. They’ll be dots on a screen, as calculations are made to point energy weapons at.
There’s no room for explosions or even loud noises, as there are no vibrations. Even a nuke exploding wouldn’t do very much, aside from the radiation it would cause.
There are also no dogfighting maneuvres, because space propulsion doesn’t work like that. There’s no friction in space.
This is especially relevant in The Last Jedi, where the Resistance is on the run from a superior First Order fleet. The story goes that the Resistance is running out of fuel, and ships occasionally drop back and get shot to pieces. But with no friction in space, the Resistance ships don’t actually need fuel to keep going. After an initial engine burn, they’ll maintain that velocity until something stops them.
In fact, The Last Jedi doubles down on this middle finger to Newtonian physics with its bomber sequence. We’ve already talked about explosions. But without gravity, there’s nothing to really pull those bombs towards the dreadnought.
Parsecs Are Misleading
Another term that probably falls into the category of “we used it because it sounded cool,” the parsec is incorrectly used in A New Hope. When Han Solo says his ship can do “the Kessel Run in less than 12 parsecs,” it sounds like a measure of time.
A parsec is actually a measure of distance — equal to 3.26 light years in length. That’s 31 trillion kilometres, or 19 trillion miles.
This is a more commonly known piece of trivia, but I bring it up because it relates to the following section.
The Hype in Hyperspace
Star Wars uses the terms “light speed” and “hyperspace” somewhat interchangeably, though the ideas are different.
Light speed is a more straightforward term. It’s impossible to go the speed of light as far as we know, unless you can reduce your mass to zero. Even if you could travel the speed of light, you wouldn’t be able to get anywhere quickly enough in the Star Wars universe.
Coruscant is over 13,000 parsecs away from Tatooine. That would take more than 42,000 years at light speed.
Given that Darth Maul was able to travel between Coruscant and Tatooine in just seven hours, that doesn’t really fit with the travel times in Star Wars. It also took just two days for Obi Wan and Luke to make that fateful trip looking for Princess Leia — even if they were looking in Alderaan places.
Hyperspace is more theoretical and vague. It usually refers to passing into some kind of different dimension where different rules apply. Slip in, do your faster-than-light travel (FTL) and pop out at the other end. The imaginative nature of this means we have no real numbers to base it on and so yes, sure, hyperspace could get you from Coruscant to Tatooine in seven hours.
Star Wars canon nods to this somewhat with the inclusion of hyperlanes, which are routes designated as safe for hyperspace travel.
Given how theoretical it all is, it’s also possible to say there’s perhaps some sort of minimum distance one travel in light speed. Which would — very generously — explain the star destroyers in The Last Jedi not being able to do a miniscule jump ahead of the Resistance cruiser.
However there are previous canonical examples of jumps into precise locations mid-battle, so… Yeah.
The Single-Biome Planet
Star Wars is one of the worst offenders of this trope, and it’s continued in the new movies. Jakku is similar to Tatooine in its desert nature. Crait is intentionally a Hoth throwback.
Planets that only have one climate are unlikely destinations for colonisation. They’re usually shown briefly, because their lack of diversity is uninteresting for story and visuals over long periods. A lot of variations on these planets are possible if certain conditions are met. Star Wars doesn’t usually bother to meet them.
Desert planets are perhaps the most likely of these, but there needs to be a certain percentage of water to sustain life and a breathable atmosphere. Ice planets are also possible if there’s a strip of warmth close to the equator, or if geothermal energy somehow sustains life and a food chain.
This can also apply to other kinds of planet-wide environments like an entire planet that’s a city, a la Coruscant. Not technically impossible, but it would rely on an immense amount of off-world support. Food and waste logistics are an obvious challenge. Less obvious are things like heat dissipation and the general effect on the population’s psyche.
As mentioned above, a lot of these are possible but require humans to live in a certain way, or by using extreme technology, or imply vast methods of support. Occasionally Star Wars visualises a situation where this is more feasible — the moisture farmers of Tatooine, for example — but this is more of an exception.
There’s a lot more to cover, though this mainly sticks to elements that we saw in The Last Jedi. There’s a whole other discussion that could be had about duelling with lightsabres on a lava planet and jumping at someone with the high ground.