Last month, Star Wars: The Last Jedi hit theaters to critical and fan acclaim — and a lot of new questions. Like, who is Broom Kid? (Temiri Blagg.) What ever happened to Snap Wexley? (Presumably sent on a mission to the Outer Rim.) And how did Leia survive violent expulsion into the vacuum of space?
Some sci-fi questions have no answers. Doubly so in a fantasy movie. We can only hope, and wait, that the as-yet-untitled Episode IX will give us the answers we seek. For others, like Leia's brief stint in the void, we need not rely on the whims of fiction when we have the ever-reliable science at hand.
Spoilers for The Last Jedi follow...
Let's set the scene. Early in the film, Leia's ship, holding the last vestiges of the resistance, is being pursued by the First Order. Kylo Ren leads a band of fighters on the attack and readies to blast the bridge where Leia, Admiral Ackbar, and others are attempting to flee to safety. Sensing the presence of his mother, Ren stays his hand.
His cohorts, however, weren't as sentimental or as informed and the bridge is fired upon, sending everyone there on a one-way, direct flight to the afterlife. It is assumed, at first glance, that Leia has been killed, along with everyone else in the room. There's a lingering shot of her motionless face before she comes to, extends a hand, and Force floats back to the ship.
There's been some commotion within the Star Wars fandom regarding this scene.
Of course, one could explain away most anything by invoking the Force, which certainly had something to do with it. We could leave it there, with a wave of the hand (Alec Guinness-style), the conversation is ended, but where's the fun in that? Those aren't the droids (or the answers) we're looking for. And, it turns out, with a bit of luck and quick thinking, it's not outside the realm of possibility that Leia could have survived her brush with oblivion.
Contrary to what popular media might have you believe, leaving the safety of your ship or space suit while off planet won't result in an immediate and explosive death. (Though, admittedly, it's not the best idea.)
So, what would really happen? First off, you wouldn't explode. Your skin has two jobs: keeping things that aren't you out, and keeping things that are you, in. And it's very good at those jobs. While you wouldn't burst, your body would swell to the limits of the skin and there is a high likelihood of spontaneous vomiting, urination, and defecation as liquids inside the body move from high to low pressure. Thankfully, Johnson allowed General Organa a classier experience.
According to experiments carried out under contract with NASA's Manned Spacecraft Center in 1964, 126 dogs were exposed to near vacuum for varying amounts of time. Their results indicated that exposure to low or no pressure for less than 120 seconds resulted in survival in every case with minimally eventful recoveries.
You also wouldn't freeze, at least not right away. The temperature of space is a moderately difficult thing to gauge and ranges anywhere from just a few degrees above absolute zero into the thousands depending on distance from a star, cosmic events, radiation, and the number of matter particles present in the area. Regardless, it's unlikely you would freeze to death before something else killed you. In fact, something rather counterintuitive would happen.
“As I stumbled backwards, I could feel the saliva on my tongue starting to bubble, just before I went unconscious,” said Jim LeBlanc, recalling his experience of accidental depressurization during a ground-based suit test in 1966.
At sea level, the boiling point of water is 212 degrees Fahrenheit (100 degrees Celsius). That's the temperature at which the internal pressure of the water matches or exceeds the external pressure of the atmosphere and molecules are freed to move away from one another. That's the reason behind lower boiling points at higher elevations. Lower pressure, less energy needed. In a vacuum, there is no external pressure holding the water together and it boils on its own.
The most immediate danger when finding yourself suddenly outside the protection of a pressurized atmosphere is that your lungs might burst. Common wisdom, and instinct, might tell you to hold your breath. After all, there's no air in space, but that's just about the worst thing you could do. The drastic difference in pressure inside and outside of your body would cause your lungs to expand until they pop. Luckily for Leia, and the resistance, the force of the blast would likely have knocked the wind out of her. Additionally, careful viewing of the scene shows Leia stops breathing when she senses the shot coming. Lungs empty: check!
Now that your lungs are intact, you can live to fight another day, or another several seconds at least. On Earth, it's possible to hold your breath for several minutes without losing consciousness. But that's because you've got all that sweet, sweet air filling your lungs. It might be uncomfortable, but you'll live. In a vacuum, your lungs recently emptied, you've got roughly 15 seconds before all of your oxygenated blood is used up. Then, you lose consciousness.
In the film, we see Leia floating in space for what might have felt like an eternity but was really only a few seconds, before she makes her way back to her ship. Granting, of course, the ability to move yourself through space (this is Star Wars, after all, we have to grant some things) it's not impossible, nor even unlikely, that Leia could come out the other side of that ordeal at least mostly intact.
The most unlikely aspect of the scene (excusing, of course, magical flight) is that it took the general so long to get back on her feet. Those dogs were up and at it in a couple of minutes. Had Leia shortened her space-nap, she could have stunned the smugness off Poe's face a few scenes earlier.
For those of you unconvinced by empirical data, there is an in-world precedent for this sort of thing, as well. Of all the questions on your mind after viewing The Last Jedi, how Leia survived shouldn't be one of them.