Planet of the Apes and Philosophy (17 page)

The situation which arises in
Escape from the Planet of the Apes
is an example of what is often referred to as the “Grandfather Paradox.” Imagine you travel into the past to a time before your mother was born, and you track down your
grandfather and, for whatever reason, you kill him. With your grandfather dead, your mother will never be born. If your mother is never born, then the question arises—where did you come from?

Many sci-fi story plots run afoul of the grandfather paradox by choosing to ignore it. Take the plot of the 1984 movie
The Terminator
. Robots from the future, having nearly won the war against humans, decide to take a radical step to eliminate the remaining human resistance forces. They send a cyborg into the past to murder Sarah Connor, the mother of John Connor, leader of the human resistance. Had the Terminator, played by Arnold Schwarzenegger, succeeded in killing Sarah Connor, we would have been faced with a variation on the Grandfather Paradox—namely, if John Connor never exists, who exactly were the robots of the future trying to kill? Why would the machines of the future send a Terminator back in time to kill the mother of a person who, for them, never existed?

The scenario that arises in
Escape from the Planet of the Apes
—where Professor Hasslein's awareness of Earth's ape-dominated future seems to enable him to avert it—sets up something like a “Grandfather Paradox” for the franchise as a whole. Should he succeed in averting the rise of the apes, the entire society which gave rise to Cornelius and Zira would never come to pass.

Of course, that's not how the story unfolds. Hasslein does succeed in killing Cornelius and Zira, but their son Milo survives, switched as an infant with a circus chimp and raised to adulthood by Señor Armando. Not only does Milo (re-christened “Caesar” by Armando between the third and fourth films) survive, but he goes on to become a leader of the ape rebellion in
Conquest of the Planet of the Apes
. Not only has Hasslein failed to change the future, it seems he may have been instrumental in setting events in motion that would lead to the rise of apes and the fall of humankind. This suggests a different sort of potential relationship between the actions of past-travelers and their impact on the future from which they departed.

The simplest way around the Grandfather Paradox is to deny that it's possible to change the past. This is not an unreasonable
thing to do, given our common-sense understanding of past events. Past events have already happened, so they are “true” for all time. Thus, they cannot be changed. To do so would simply be a logical contradiction. I cannot travel back to 1930 and kill my grandfather, because it's an eternally true fact about the world that my grandfather did not die in 1930. If I travel into the past, I can only do those things that were done in the past by a time traveler. (Me!) So I cannot travel back to 1930 to kill my grandfather, but I could travel back to 1963 and assassinate John F. Kennedy. But—and this is important—only if it has always been true all along that the “second gunman” conspiracies about the JFK assassination were true, and that second gunman was myself, a time traveler from the future!

This version of time travel, where time travelers cannot change the past, but only bring about past events as they originally happened, relies on the concept of “closed causal loops.” The idea is that time travel can proceed only via closed loops where past events can be
caused
by a time traveler, but are never
changed
by a time traveler. This concept can lead to compelling and paradox-free time travel stories when handled carefully. (My personal favorite is the 1995 movie
12 Monkeys
, directed by Terry Gilliam and starring Bruce Willis.)

At first glance anyway, the third and fourth
Apes
movies seem to obey the rules for past time travelers as dictated by this “closed causal loop” concept of time travel. Not only do the apes who travel back to the twentieth century not change their past, they take part in those very activities that brought about the future from which they departed.

What are we to make of time travel stories in which the time traveler changes the past, thereby altering the future that they knew? Are they simply wrong? Is there any room in either physics or philosophy for the notion that we can change the past? There does seem to be room for another way of thinking about time travel into the past.

An alternative model of time travel asserts that when a time traveler changes events in the past, he or she simply creates
another timeline that exists independently of the one they departed. The future they are familiar with ceases to exist, or at least exists now only in an alternate, parallel reality. Events in this new timeline unfold in a way that places no limits on the actions of the time traveler. You are free to kill your grandfather, or Kennedy, or Hitler, or whomever you wish in the past. The Grandfather Paradox is sidestepped, since the answer to the question “If my grandfather died before my parents were born, where did I come from?” becomes—“You came from the future of an alternate universe.” In this conception of time travel, the traveler is more than just a traveler through time—they are a traveler between realities.

This approach to time travel is encountered frequently in science-fiction stories. One somewhat silly example comes from the 1985 comedy
Back to the Future
. When Marty McFly arrives in the past, he accidentally prevents his parents from meeting, setting up a version of the Grandfather Paradox that threatens his existence. When he tries to set the situation straight by arranging for his parents to meet at the school dance, he also changes some of the circumstances of the past, by for example convincing his father George McFly to stand up to the bully Biff. The result of this change to his past is evident when he returns to the future (his present) to find his parents as hipper, thinner, and more successful versions of the ones he left originally. By changing the past, Marty gave rise to an alternate universe with an alternate history.

A more recent movie that takes this approach to time travel is J.J. Abrams's 2009
Star Trek
reboot. When the troubled Romulan, Nero, pursues an elderly Spock through a black hole and back in time, he sets off a whole sequence of events—from the death of Kirk's father to the destruction of the planet Vulcan—that change their past. This means that the young crew of the
Enterprise
will experience an entirely new timeline from the one described by the events of the original series. This frees the story from the implications of the Grandfather Paradox altogether. (It also frees the screenwriter and director from the requirement of appeasing demands of continuity and consistency from fans of the franchise!)

If we examine the
Planet of the Apes
movies from this angle, we can interpret the small inconsistencies between the films as evidence that the various installments of the series are taking
place in multiple parallel timelines. Consider the inconsistencies that are evident between the third and fourth films in the series. In
Escape from the Planet of the Apes
, Zira and Cornelius describe the events that lead up to the fall of humankind. After a plague kills off the world's dogs and cats, humans domesticate apes as pets. “They were quartered in cages, but they lived and moved freely in human homes. They became responsive to human speech. And, in the course of less than two centuries, they progressed from performing mere tricks to performing services.” And then some three centuries later, according to Zira, the apes began to recognize their enslavement and to quietly rebel. The stage was set for a full-scale revolution when a chimpanzee named Aldo was the first ape to speak. He said “No.”

Contrast this story with the plot that unfolds in the next movie,
Conquest of the Planet of the Apes
. Only twenty years elapse from the birth of Caesar until the time when apes are being used in a service role by humans. And it's Caesar himself who instigates what seem to be the first battles of the ape revolution. Speaking much more than a simple “No,” he delivers an impassioned speech about the coming ape domination.

What happened to Aldo and the slow, five-hundred-year process of ape advancement and growing discontent? Could it be that by traveling into their past and giving birth to the infant Milo, who would become the revolutionary Caesar, Zira and Cornelius changed their past and set into motion a series events that would accelerate the rise of the apes by centuries? As viewers, we could simply chalk up the inconsistencies as sloppy attention to continuity on the part of the screenwriters. But we might instead use the discrepancies as a case-study for the multiple-timeline conception of time travel.

There is some direct support for the multiple-timeline idea from the
Apes
series itself, through one of the few explicit statements made about the nature of time by any of the characters. In
Escape from the Planet of the Apes
, Dr. Hasslein explains to a television reporter that

           
Time is like a freeway with an infinite number of lanes—all leading from the past into the future, however, not into the same future. A driver in lane A may crash while a driver in lane B survives. It follows that a driver, by changing lanes, can change the future.

He seems to be advocating for a view that allows many alternate futures to unfold, depending on the choices made in the present. This interpretation of the relationship between the certain present and the uncertain future is not far from a view espoused by a number of contemporary physicists.

The multiple-timeline version of time-travel may seem like something of a cheat—a way to sidestep the grandfather paradox in a way that permits sci-fi plots that are paradox-free without being needlessly convoluted. But it turns out that there may be some support for this vision of time from within modern physics, from a particular interpretation of the theory of quantum mechanics called the Many Worlds Interpretation.

One of the lasting philosophical issues facing physics is the question of how to interpret the probabilistic nature of quantum theory. In quantum mechanics, the behavior of subatomic particles is not described by a precise trajectory through space and time, the way that Newton's Laws enable us to calculate the precise path of a planet around the Sun. Instead, the behavior of a subatomic particle is described by a quantum mechanical wave-function that only gives the probability of various outcomes. The question of what actually happens when a potential outcome becomes an observed result is still the source of much debate among physicists and the source of considerable confusion within popular treatments of quantum mechanics.

The most common way to deal with this transition from probability to actuality is simply to acknowledge that when we observe a quantum mechanical system, we introduce a discontinuity of sorts into our description of the situation. Before we make our observation, the theory demands that we describe a system using a wave-function which handles all of the potential outcomes probabilistically. But after we've observed the system, only one of the potential outcomes is actualized. So the old wave-function no longer applies, and is of no use to us. This transition is usually referred to as the “collapse” of the wave-function.

There's another more exotic interpretation of this transition from probability to actuality, which is that all of the possible
outcomes are actualized in separate universes. This so-called “many-worlds interpretation” suggests that every time there is a “choice” available at the subatomic level, the universe splits into multiple parallel versions of itself. Every possible outcome of the event is equally real in some parallel universe. This leads to an unimaginable number of universes branching out from our own every instant. Since these parallel universes are unobservable and undetectable from within whatever universe you find yourself, it's not quite right to call this the “Many Worlds Theory.” The word “theory” suggests a scientific model which makes testable predictions, and most physicists agree that the Many Worlds idea does not. It is simply a conceptual framework designed to explain how a theory which is purely probabilistic at the microscopic scale could give rise to a universe that appears to have a single well-defined reality at the macroscopic scale. The advantage of the Many Worlds interpretation is that it de-emphasizes the role of the observer in the process, since the “collapse” of the wave-function, which seemed like something that was “caused” by the observer, never occurs in this model.

The multiple-timeline version of time travel seems to agree in its basic structure with the Many Worlds interpretation of quantum mechanics. If every choice that's made in the universe, from the subatomic level to the conscious level, can give rise to branching alternate realities, then why shouldn't the actions of a time traveler do the same?

The time traveler is just doing what we all do all the time anyway—making choices that lead to a particular future. The idea that there is only
one
such future is a side-effect of the fact that we ordinarily only get to observe one of those potential universes. But the time traveler gets to see the effect of these multiple choices directly, by traveling from a timeline where the universe unfolded in one way, traveling back in time, changing the circumstances, and seeing the universe unfold in a different way. If this picture of time travel is correct, a time traveler is as much a traveler between universes as they are a traveler between times.