In the concluding remarks of my previous piece about the physics of Concord Dawn, I argued that one could use science to think about how something unusual in a work of fiction might happen, and its consequences and implications, rather than just calling it a flaw that was not addressed and must be pointed out. After The Last Jedi‘s release, however, many chose this second option when faced with an element from the film’s opening sequence: bombers in space.
The argument generally goes like this: it makes no sense that Resistance bombers would attack a First Order Dreadnought by flying over it and dropping their bombs, since everything happens in space where there is no gravity, and therefore the scene was just filmed that way because that’s how bombers operate on Earth and it looks cool. Mind you, that might well be the actual reason! But since we’re thinking about physics, we could go a bit deeper than this and see where it takes us. One can’t invoke the planet’s gravity to explain bombs falling onto the Dreadnought, since the ship is not oriented with its ventral side directly facing D’Qar, although its artificial gravity seems to extend a bit beyond its topside hull (as seen when debris from explosions and destroyed TIE fighters fall towards it). There’s also artificial gravity inside the bomber, as an important plot point makes us painfully aware, and that alone could have propelled the bombs away. But it turns out that gravity was never necessary—according to TLJ’s Visual Dictionary, the bombs are launched from the bomber by electromagnetic means.
Airless aerial combat
Couldn’t the bombers, then, have attacked from any angle or launched the payload from a distance without making it look exactly like it would on Earth? Well, I guess they could, and we could dismiss the scene as unrealistic. But let’s think a bit more about it. Perhaps TIEs would have time to shoot at missiles or bombs if they came from further away, or tractor beams could be used to deflect them. Maybe by delivering them up close the bomber’s shields protect them for a longer time, and the bulk of the Dreadnought can be used as partial cover. But more importantly, this kind of bombing run in space is something we’ve seen in Star Wars since The Empire Strikes Back, and has also appeared in Rebels and Rogue One. A design that launches the explosives in a direction perpendicular to the flight path allows the ship to fly parallel to the surface of the target instead of directly at it, avoiding the need to reduce speed and change direction at the last moment. Also, as a planetary bombardment weapons platform, one would expect the ventral side of the Dreadnought to be better protected to withstand planetary defenses, so maybe the dorsal side was more vulnerable and reliant on anti-fighter batteries (destroyed by Poe). Perhaps the artificial gravity would repel the tiny bombs if released ‘upside-down’ on the ventral side. All of this leaves the sequence in the film as the best approach in those circumstances, even accounting for the physics.
Another common criticism of Star Wars spaceflight is that fighters would not be able to turn or maneuver with all their engines facing aft. I feel the need to point out that in many actual space launches, rockets change and adjust their trajectory with their main engines only, just by altering their throttle and orientation—and even some combat fighters use this technique. But even then, TLJ also shows Poe’s X-wing tracing a tight circle by pointing the nose inward and engines toward the outside of the curve, providing the necessary centripetal acceleration to do this maneuver in space. We also see an escape pod using maneuvering thrusters to orient itself, just like our actual spaceships do. So when one is ready to use physics to claim that something in a film is wrong, I would advise caution and making sure first that our assumptions are not too simplistic, lest the same arguments dismiss as impossible something our own technology does all the time.
After that, one should also be aware of how future technologies could circumvent these problems. The Last Jedi, with the First Order’s new hyperspace tracking abilities, provides a case of something that seemed impossible even for the characters living in that universe but turned out not to be anymore. The mind-numbingly high computer processing power needed for the task is now part of Snoke’s ship. Perhaps the huge size of this mega destroyer also allows for a wider distribution of sensors to track their prey even better. One can think of more implications of the achievement of a seemingly impossible feat rather than just dismiss it.
Forced extravehicular activities
The tracking of the Resistance fleet leads to an attack in which the bridge of the Raddus is destroyed and the crew expelled into space. But not long afterward, an unconscious Leia wakes up and uses telekinesis to go back to the safety of her ship, in urgent need of medical assistance. The scene raises some questions, but yes, hard vacuum is survivable for a short time, as Pablo Hidalgo clarified on Rebels Recon (they probably wanted to make sure we knew this for TLJ), and Leia stayed in space for less than two minutes, if I timed it correctly. When faced with such a vacuum the main problem by far is the lack of oxygen, which would make a human lose consciousness in about ten seconds and cause brain damage in a few minutes. Freezing to death, however, is not. It is in fact harder to lose body heat in the vacuum of space than on, say, Hoth’s surface, since you’re not in contact with a lot of molecules that would absorb that energy, and you can only cool down by emitting infrared light.
The frost on Leia’s skin could be a mistake, then (it’s a common misconception, after all). But in the spirit of this post, we can think deeper about alternative explanations. Something worth remembering is that liquid water isn’t stable in a vacuum, and will quickly turn into ice or vapor depending on the temperature. Exposed skin will cool down a bit because the evaporating water takes away some energy, but not enough to freeze. However, when the air that filled the bridge expands rapidly into space its temperature drops, and moisture condenses into droplets that might then become ice. Perhaps some ice particles were deposited on Leia’s skin, attracted by static electricity, and were in the process of evaporating when we saw her again.
But the dangers of vacuum exposure are many. The loss of pressure would make fluids leak into soft tissues, and gas in internal cavities and organs could expand causing damage. Nitrogen bubbles would form in the blood (like when a scuba diver ascends too fast), changes in pressure and oxygen concentration would make it hard for the heart to pump blood, and continuous release of water vapor from inside the lungs could cool them down too much and form ice inside the airways of the respiratory system. A very dangerous situation occurs when the person holds her breath before the rapid decompression, because expanding air would rupture the delicate tissue in the lungs.
However, one would assume that someone with decades of experience in a space-based military operations would have enough training to avoid this, plus Leia’s mental connection with Kylo at the time might have provided some warning. We also don’t know the amount of protection her instinctive use of the Force could have provided against the lack of pressure (the Force starts affecting ice and dust particles near her hand before she flies back to the cruiser, and her eyes are not bloodshot when she then opens them nor her skin swollen, for instance), and the rest of the damage could be accounted for by her unconsciousness and need of advanced medicine after the event. People also wonder why no air is sucked into space when they open the door for her. I thought about it myself until I noticed that the entrance to the bridge has two doors, which might act as an airlock. Plus there’s also the possibility of a security field retaining the air inside, of course.
Close encounters of the lightspeed kind
One of the climactic moments of the film arrives after the Resistance cruiser has been chased for many hours in deep space by a First Order fleet and the massive bulk of Snoke’s Supremacy, kept out of range by constantly accelerating, as evidenced by support ships falling behind when they run out of fuel (also, in an accelerating reference frame, the otherwise straight trajectories of the First Order’s barrage would turn into parabolas if they’re not fired exactly straight ahead, as we also see!). In a desperate maneuver to protect fleeing transports carrying what’s left of the entire Resistance, Vice Admiral Holdo decides to turn the cruiser around and engage the hyperdrive while aiming at the pursuing mega Star Destroyer.
After years of musing about the possible outcome of such a collision, and with a familiarity with the effects relativistic speeds can have on matter, I had resigned myself to disappointment when the eventual larger, but otherwise quite normal, explosion would appear on screen. So let me tell you up front, I can’t possibly overstate how delighted I was when I witnessed the visual display Rian Johnson had chosen for this event, only for my enthusiasm to go even higher when I read this article detailing the things they considered when developing the scene. The cruiser not only tears straight through Snoke’s ship due to its impossible speed, but an incredibly bright stream of particles and debris is created. The artists thought of the interactions that would take place at the atomic level and were inspired by actual physics experiments for the resulting look. Even the debris hitting smaller ships is still going so fast that it immediately tears them apart. The surreal visuals are motivated by massively underexposing the picture due to the extraordinary energies involved. And the whole scene is silent.
I am still in awe over how physics were used to enhance the visual impact and ‘cool factor’ of those shots, an approach I heartily support at every opportunity. But Star Wars is viewed by many as a franchise that never needs to adhere to known science when doing so would hinder the storytelling, with elements like sound in space pointed out as prime examples of how boring things would be otherwise. Although it is possible to depict silence in space without losing spectacle (and examples like Firefly, Planetes, Gravity or the subtle method used in the reimagined Battlestar Galactica come to mind), one can acknowledge the stylistic choice made for an audiovisual medium in this case. You can even imagine that we’re shown these scenes with sound but none was actually heard in the event (I believe every time a Star Wars novel has made a reference to sound in space was to point out the absence of it, with Cobalt Squadron the most recent example).
But in less clear examples of apparent scientific inaccuracy, there’s always a choice between two different paths for the viewer to take. One can lead to anger at storytellers for not respecting a set of rules, or even acceptance of the fantastical elements that will always underlie Star Wars. The other—trying to see how a scene could be justified within the bounds set by those rules—can lead to unexpected understanding, or even new threads of consequences to be followed later. If you really want to think about physics, this one is my personal favorite. There’s more fun to be found that way.