Philipp Berghofer
Prophetic visions of the future feature prominently in our favorite space opera. Luke has them, like his father before him. The Skywalker saga is basically the story of Anakin being unable to let go, willing to do anything to prevent his prophetic visions from becoming true. The tragedy, of course, is that the very actions he undertakes to save his beloved Padmé lead to her demise. Are the events in the Star Wars universe set in stone – that is, deterministic – or could Anakin have chosen different actions that would lead to his living with Padmé happily ever after? Can we change the future or is our fate set in stone? Is the future real, just as past and present appear to be? Is time travel logically possible? Can we change the past? While questions like these are debated in contemporary metaphysics, they are also raised by the Rebels episode “A World Between Worlds.” Here, time travel is finally introduced into the Star Wars lore – a surprise, to be sure, but a welcome one.
But, beware! Do not underestimate the menacing paradoxes of time travel!
Anakin loves Padmé, and the thought of losing her is unbearable to him. In Revenge of the Sith, Anakin is plagued by visions of the future, of his beloved dying. He cannot accept this fate; this future must be prevented at all costs. To do so Anakin is willing to pursue “a pathway to many abilities some consider to be unnatural.” The fact that his crusade for power, intended to save Padmé, turns out to cause her demise is the defining element of the tragedy of Anakin Skywalker. As we'll see, these events pose challenges to thinking about time, determinism, and free will.1
Jedi Master Luke Skywalker's later life is shaped by a similar tragedy. Foreseeing all the horrors that'll be caused by Ben Solo, Luke ignites his lightsaber. Ben's realization that his uncle is on the verge of murdering him is the crucial factor by which he justifies his later wrongdoings.
This idea that the future is set in stone and that our attempts to prevent future horrors actually cause these horrors is common in storytelling. In Greek mythology, Oedipus becomes aware of the prophecy that he will kill his father and marry his mother. In Harry Potter, Voldemort learns of a prophecy that a child will be born who will become his nemesis.2 In Star Wars, Anakin has prophetic visions of Padmé's death that echo visions he'd previously had of his mother's death, which he was unable to prevent in Attack of the Clones. Such stories seem to imply that while we can cause future events to occur, we cannot change what must occur.
Similarly, many time travel stories are based on the idea that we can cause past events but cannot change them. In The Terminator, the eponymous cyborg travels back in time to kill Sarah Connor so that her son, John, is never born and thus cannot become the leader of the human resistance. However, the Terminator's actions cause Kyle Reese to be sent back in time to save Sarah; he makes love with her and she gives birth to John.3 In The Prisoner of Azkaban, Harry Potter and his friends mistakenly believe that an innocent hippogriff has been killed. They travel back in time to prevent this death, but it turns out that the hippogriff never has been killed and that its death had already been prevented by the actions of the time traveling friends.
Time travel stories in which the past is changed are in danger of being inconsistent or plagued by paradoxes. Imagine that it's possible to travel back in time and you kill your grandfather before he was conceived. You've just undermined your own existence! But if you have never existed, then you have never traveled back in time to kill your grandfather. So you live only if you do not live? Paradox!
We do not have to invoke fancy examples of undermining your own existence to see that changing the past leads to logical problems. Imagine that George Lucas travels back in time and makes some changes to A New Hope (ANH) so that, in the cantina scene of the 1977 original cut, Han does not shoot first. Lucas has changed the past. But this means that “Han shot first” is both true and not true in 1977! Many philosophers believe that time travel to the past that does not change the past is logically possible.4 Whether it's possible or not in our world, let us proceed as if time travel is possible and has actually happened in Star Wars.
It's the year 0 BBY (Before the Battle of Yavin) and, perhaps, Ezra Bridger's most desperate hour. His Jedi mentor and friend, Kanan Jarrus, has just died, and Ezra's about to enter the Jedi Temple on his homeworld, Lothal. A painting of the Mortis gods serves as a portal. Ezra manages to open the portal and arrives at the “World Between Worlds,” a plane within the Force beyond space and time, binding all moments in time together.5 There are a vast number of portals that allow travel through space and time, but this one is a “pathway between all time and space” and “he who controls it controls the universe.”
Shortly after entering the World Between Worlds, Ezra finds a portal in which he sees Ahsoka Tano dueling Darth Vader. This event happened in 3 BBY. We see Ahsoka fighting bravely but about to be slain by her former master when Ezra reaches into the portal, grabs Ahsoka, and pulls her through, saving her life. Was Ahsoka originally slain by her former master and then Ezra changed her fate? Is this event best understood as Ezra changing the past or merely causing an event in the past? Ezra believes that changing the past is possible. After saving Ahsoka, he wishes to save his recently killed mentor, Kanan. He tells Ahsoka, “If I can change your fate, I can change his.” However, it's far from clear that changing the past is logically possible. At the moment Ezra is about to save Ahsoka, he believes that he knows this fact: “In the year 3 BBY Ahsoka was slain by Darth Vader.” Yet when he saves her, that statement cannot be a fact. Could a statement be both true and false? This would be a logical contradiction!
Maybe by entering the portal, Ezra created an alternate timeline: in one timeline Ahsoka was killed and in the other Ahsoka lives! There's no consensus on whether this form of intervention in history should even be understood as an instance of changing the past at all. As seen on screen, the fates of Ahsoka and Kanan are very different. We see Kanan die on screen in the Rebels episode “Jedi Night.” We never see Ahsoka die in her duel with Vader two seasons earlier in “Twilight of the Apprentice.” So, our story may be similar to the hippogriff story in Harry Potter. Harry and his friends believe the hippogriff to be dead. However, the hippogriff never died, having already been saved by the time travelers – without them changing the past! Similarly, Ezra may have believed Ahsoka to be dead, but in truth she never died, having been saved by the actions of time traveling Ezra. But what about Kanan?
Ezra and Ahsoka find a portal showing Kanan's dying moments. Ezra has to relive the moment when Kanan sacrifices his life for Ezra and his friends, but he's still intent on saving Kanan just as he saved Ahsoka. But Ahsoka warns, “Kanan gave his life so that you could live. If he is taken out of this moment, you all die.” Let us assume Ahsoka's right and there's no way of saving Kanan without Ezra dying. Is this a “mere” moral dilemma, in which Ezra has to make a terrible choice: sacrificing himself or letting a friend die? No, this scenario's also rooted in a metaphysical dilemma called the “grandfather paradox.” If Ezra saves Kanan, Ezra dies in the past. But if Ezra dies in the past, then Ezra cannot later enter the World Between Worlds and save Kanan. If Ezra dies before entering the World Between Worlds, no one will save Kanan. But if no one saves Kanan, then Ezra lives and can save Kanan. Kanan can live only if Ezra dies, but if Ezra dies, Kanan cannot live.
But the problems do not stop here. Imagine that Ezra and Ahsoka succeed in saving Kanan, but that Ezra does not die. Past‐Ezra, present‐Ezra, Ahsoka, and Kanan are happily reunited. But present‐Ezra has mourned Kanan's loss. This will not be past‐Ezra's future because past‐Ezra has no reason to mourn Kanan's loss. Ezra has changed the past, but also created a number of contradictions. Has Kanan lived or died? Has Ezra mourned or not?
In famous time travel stories such as Back to the Future, the protagonist travels to the past, changes the past, and then returns to a present quite different from the one they left. But philosophers agree that such stories do not make a lot of sense.6 In fact, if we agree that there's only one time and one universe, time travel that changes the past seems to be impossible.
Let us further pose the question of whether the past, present, and future are equally real. In contemporary philosophy of time, there are three main approaches to this question: presentism, eternalism, and the growing block universe. Presentism is the view that only the present is real. Only present objects and events exist; past and future objects do not. You exist but Abraham Lincoln does not. Presentism may seem like a commonsense view: it's somehow strange to say that, right now, Abraham Lincoln is equally real as I am. On the other hand, with presentism it's not so easy to make sense of statements about the past and future. Is it true that Abraham Lincoln served as the sixteenth president of the United States? To what state of affairs does the sentence “Abraham Lincoln served as the sixteenth president of the United States” correspond? If the past does not exist, can there be historical facts? Furthermore, presentism seems to be in tension with modern physics. According to special relativity, concepts such as “simultaneous” and “now” are relative. There's no objective now.
Eternalism says that the past, present, and future are equally real. Right now, as you are reading this, Abraham Lincoln is as real as you are; the statement that he served as the sixteenth US president is true in the same way as the statement that you are thrilled by the text you are currently reading. Time is similar to space: if you are standing at the gates of Skywalker Ranch, you cannot see what is 50 miles north, south, east, or west from you, but those places do exist. Different times are as real as different places. The world in which we live is a four‐dimensional space–time that resembles an unchanging block: eternalism is also often referred to as the “block universe” theory of time. Eternalism also implies that there's no open future. At every point in time, it's true that Padmé dies in childbirth in 19 BBY. Often it's thought that this implies determinism, but this may be too hasty a conclusion.7 Determinism says that the future is set in stone because the future non‐accidentally follows from what has happened before. But determinism does not imply that the future yet exists. Eternalism says that the future exists, but it does not imply that the future is determined or even caused by previous events. It may be sheer coincidence that Abraham Lincoln became president. But if it's true, it has always been true. Finally, for the growing block theory, the past and present are real, but the future is not. This view best accords with our commonsense idea that the past is set in stone but the future is open.
These views on the nature of time have crucial implications for whether and how time travel may be possible. Presentism seems to be incompatible with time travel. If the past does not exist, how could I travel there? I cannot travel to a non‐existent space, so how I could travel to a non‐existent time? This argument is intuitive, but there are counterarguments.8 Eternalism seems best suited to allow for time travel: if I can move from place to place, perhaps I can also move in time. Of course, to say that time travel is possible in any of these senses does not imply that it's physically possible. Also, time travel paradoxes still lurk!
In the growing block picture, traveling to the future seems impossible but traveling to the past should be possible. However, there's one fact about the growing block that makes time travel particularly scary. The growing block contains an objective present. The universe consists of everything that has happened from the beginning of time until that objective present. So if the objective present is first located in 42 BBY and then grows until it's in 0 BBY, the universe contains much more than before. For instance, in 42 BBY the universe did not contain Grogu (born in 41 BBY) but in 0 BBY it does. Now imagine that when Tarkin is informed toward the end of ANH that there's a danger that Rebel pilots could destroy the Death Star, Tarkin does not stay on the Death Star. Instead, he enters a time machine and travels from 0 BBY to 42 BBY. Imagine further that Tarkin is performing the sort of time travel that Sara Bernstein calls movable objective present (MOP).9 MOP time travel not only temporally relocates the time traveler but also moves the objective present. Accordingly, by time traveling, Tarkin not only moves himself to 42 BBY, he moves the objective present to 42 BBY. If Tarkin's in a growing block universe, then, by time traveling, he's shrunken the whole universe. And since Grogu has not been born in 42 BBY, Tarkin has killed Baby Yoda! Or more precisely, he's erased Grogu from existence.
What does this “metaphysical mumbo jumbo” tell us about the reality of the Star Wars universe? First, since Ezra could travel to the past, the past seems to be as real as the present, so presentism seems to be ruled out. What about the future? Is the Star Wars universe an unchanging block or a growing block? This is difficult to pin down. When Ezra is in the World Between Worlds we hear familiar voices whispering famous words from both before and after the events of this Rebels episode. Also, when Rey touches Luke's lightsaber in The Force Awakens, she has visions of past and future events. This may indicate that the past and future are equally real.
However, at the end of our Rebels episode, we hear a Mortis god, the Son, say, “The future, by its nature, can be changed.” Remember that the commonsense intuition that there's a difference between the past and the future (the past is fixed but the future is open) is one of the main motivations for accepting the growing block theory. In Star Wars it's particularly important that the audience perceives that it matters what the protagonists are achieving – that there is some risk of their failure. Of course, even in the growing block universe, we do not change the future. It's not like there's one future, then a person time travels and now there's a different future. Right now, there's no future at all. And once the objective present has moved from 42 BBY to 0 BBY, what's happened between 42 BBY to 0 BBY is not the future but the past and cannot be changed anymore.
Of course, the kind of time travel we witness in Rebels is not the typical kind that involves a time machine. Instead, time travel works by entering a place, the World Between Worlds, that connects different points in time and space. In terms of modern physics, the portals in the World Between Worlds may be understood as traversable wormholes. A wormhole, also known as an Einstein–Rosen bridge, links two disparate points in space–time. A wormhole, in theory, could link points that are far, far away – many light‐years, away in fact. Wormholes are consistent with Einstein's general theory of relativity, so it's believed they are physically possible.10 However, so far, we have not observed any, so it's unclear whether they actually exist.
In pop culture, wormholes appear in franchises like Stargate, Star Trek: Deep Space Nine, and the Marvel Cinematic Universe (where the Bifrost Bridge in Thor [2011] is referred to as an Einstein–Rosen bridge). In these examples, wormholes allow travel in space, but not in time. Physicists have speculated that if wormholes exist, they could be used to make time travel possible. Such a time travel story based on real but speculative physics is portrayed in the film Interstellar (2014).11 Time travel that works by entering a place that warps space–time, rather than by entering a machine, is sometimes referred to as warped time travel.12
The nature of time and the possibility of time travel have attracted and captivated humanity for centuries. Here philosophy, physics, and science fiction meet, inspiring each other. Particularly fascinating are the paradoxes that time travel seems to involve. Philosophers typically hold that it's impossible to travel back in time in a way that would create a grandfather‐style paradox. You do not have to worry that when traveling back in time you'll kill your own grandfather, because you'd fail anyway. Of course, we do not know what would really happen if we traveled back in time. In some fictions, time travelers do cause paradoxical situations. In a recent episode of Marvel's What If…?, Doctor Strange causes a grandfather‐style paradox and destroys his whole universe! We should thus be grateful to the metaphysically well‐informed Ahsoka for preventing Ezra from causing such a paradox. Philosophy saved the Star Wars universe!