Disclaimer: This post is a teaching tool that uses Star Wars to explain a phenomenon observed in particle physics, not a forum to exchange opinions or critiques on the movies themselves. Comments that share an individual’s views on the creative decisions or direction of the Star Wars franchise will be removed.
The saga that has captured the imaginations of kids and adults across the world since 1977 will be coming to a close this week with the release of Star Wars: Rise of Skywalker. I, too, have been enchanted by the stories from a galaxy far, far away – to this day I still will automatic doors to open with the wave of my hand.
In addition to being a huge fan of the movies (and tv shows and books and comics), I’ve also loved Star Wars as a teaching tool. Not because the films pay any adherence to scientific accuracy, but because the ideas and technologies provide a good example of how science concepts could be applied in reality. So as I rewatched each film in preparation for the final installment of the Skywalker story, I found myself wondering how, scientifically speaking, Luke Skywalker could project himself across the galaxy to dupe his nephew at the end of The Last Jedi. And as it turns out, there is a real, verified science concept that allows for particles to influence each other even when they are separated by very long distances.
It’s called quantum entanglement – in which the properties of one particle influences the properties of a separate article. In this thought exercise, I’ll explain quantum entanglement and a few other concepts in particle physics using the force projection powers exhibited by Luke Skywalker. Just remember this is no more than a fun way to explain the mysteries of our universe, not to prove the scientific accuracy of a Star Wars movie.
Before we tackle the complicated idea of quantum entanglement, we need to understand some fundamentals about quantum mechanics, the theory that describes how very small particles behave. The rules of physics that Issac Newton described and we regularly observe in our daily lives don’t apply at the subatomic level. Objects such as electrons, photons, and quarks have the properties of both a particle and a wave (called wave-particle duality). We also cannot know with complete certainty the position and momentum of a particle at the same time. And measurements can only be described in terms of probability- we can only make a guess as to where or even if a particle exists.
But the main idea we need to understand before we get into how one could project themselves across the galaxy is the Law of Superposition. This law says that quantum particles can be in multiple states at once. For example, spin is a directional property that describes a particle’s angular momentum. Subatomic particles can have either an up or down spin (they’re not actually spinning like a top), but what’s bizarre is that they can occupy both values at the same time until we measure it. That is to say, the properties of a particle are not defined until they are observed.
Physicist Erwin Schrodinger provided a thought experiment to explain this phenomenon. Schrodinger imagined a cat inside of a metal box, and with it, a poison that has a 50% chance of being released upon opening the box. While everyday logic would tell you that the cat would be alive until the poison is released, the Law of Superposition says that until we observe the cat by opening up the box, it is both dead and alive at the same time. In fact, by opening the box, we force Schrodinger’s eponymously named cat to occupy either dead or alive, with the probability of the cat being in either state at 50%.
If this sounds hard to wrap your head around, you’re in good company. Albert Einstein had trouble believing that particles could occupy two separate realities at the same time. Yet nearly 100 years after Erwin Schrodinger showed that objects can occupy multiple states at once, it has become one of the most verifiable aspects of quantum physics. The data doesn’t lie: experiments have shown over and over and over again that particles have different properties at the same time. It’s so reliable in fact that scientists and engineers have begun applying it to technology. The quantum computer, whose bits can occupy the infinite states between 0 and 1, are already in use and far outpace the power of current digital computers whose information must be stored either 0 or 1.
But if occupying two different states at the same time sounds strange to you, quantum mechanics is about to get even weirder
Quantum entanglement at a distance
In addition to all the other strange things going on at the subatomic level – superposition, wave-particle duality, and everything relying on probability – there’s another phenomenon that allows for particles to influence one another: quantum entanglement. Quantum entanglement occurs when two particles interact physically, they can influence the properties of each other even if they are miles or even light-apart!
How does it work? Say we fired a laser through a special crystal that caused individual photons split in two. After allowing each photon to travel, we observe one, forcing it into one state or the other. When observing Photon A, we see it occupies the up-spin state. But Photon B, now having traveled some distance away from it’s entangled photon, would be observed in the opposite state, down-spin. Despite having no physical bridge or messenger particle traveling between them, each photon takes up the opposite state as it’s entangled partner.
If that’s not bizarre enough for you, Photo A’s influence on Photon B is up to 10,000 times faster than the speed of light, and could possibly be instantaneous! That is to say, information is somehow transmitted well past the universal speed limit of 3.0 x 10^8 meters/second, the speed of light. By observing one particle, we force it to occupy one state or the other, and by doing so, we force another, complete separate particle to move to the opposite state, no matter if those particles are separated by a hundred miles or by a hundred parsecs. The ever pithy Albert Einstein called this “spooky at a distance”, and thought the idea an entangled system was bantha fodder.
Yet in the decades after quantum mechanics was first described, experiments have shown with a high degree of confidence that quantum entanglement is real. The latest of which involved observing photons emitted from quasars several billion light-years away using a pair of telescopes on the Canary Island of La Palma. At the end of the test, the team found that indeed, entangled photons did influence each other, even if they’ve traveled across the galaxy or beyond. While we do not have an explanation for how quantum entanglement works or what it means for the broader rules of physics, data have verified it’s existence.
The mystery of the Force
In The Last Jedi, Luke Skywalker can use his force powers to project himself across the galaxy to confront his nephew on Crait, while still sitting on Ahch-To, the planet home to the first Jedi temple. Does quantum entanglement really make this possible? Well, technically, yes – if you can influence the right amount of photons, you could make the observer see something that wouldn’t necessarily be there. Luke could be observing photons on one planet that would influence the state of other, entangled photons on another. However, there are some complications.
First, the photons on Ahch-To and the photons on Crait would already have to be entangled – that is to say, at some point, they would have had to have some sort of physical interaction. This isn’t impossible, but it would require a lot of planning, perhaps millions of years, to get the entangled photons across the galaxy and where they needed to be at the correct time. Luke, who was never much of a planner, would have needed some serious foresight to entangle the photons necessary for this feat. And, having been only 53 years old at the time of his death, it would mean both Crait and Ahch-To would have been suspiciously close to one another for the photons to travel the vast distance between them in Luke’s lifespan. It seems implausible that the place where Luke went into hiding was around the corner of an old rebel base.
Secondly, there’s the complication of the number of photons. Consider that 100-watt bulb gives off 3×10^20 photons every second. The sequence in The Last Jedi in which Luke is performing the force projection is around 5 minutes. Assuming that at least as many photons as a 100-watt lightbulb would be viewed by Kylo Ren during that time, we can say without doing the math ourselves that’s a lot of photons that need to be influenced in the right way at the right time. No wonder Luke died of exhaustion!
Lastly, there is the issue of “forcing” a photon to do something. Entangled particles are forced into a state when it’s partner is observed, not if you force a particle to occupy one property or another. If we were trying to get a photon to behave a certain way, influencing its entangled partner wouldn’t do the trick. It’s what would make faster than light communication using quantum entanglement more or less impossible. So while it’s possible to cause a subatomic particle like a photon to occupy one quantum state or another, you couldn’t make it behave any way you want.
One thing we can say though is that quantum mechanics, much like the Force, works in mysterious ways. We are still learning how the smallest particles behave and there are major questions to answer on many different aspects of our universe, including gravity. Until then, the Force will be with you – always.