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The International Writers Magazine: 21st Century Futures

Knowledge, Science and the Problem of Time Travel
Kimberly Pfeifer

n the 2004 film "The Butterfly Effect" the movie’s main character, Evan Treborn, finds that he can travel backward in time and change past events in his childhood, which in turn result in altered future outcomes. The scenario itself is hardly novel and appears in numerous works of theatrical as well as literary fiction. But does the concept of time travel belong solely to the realm of science fiction or is it a possibility?

In the essay "Time Travel: Possible or Impossible?" John Hospers endeavors to show that time travel (at least in the sense of traveling backward in time) is logically impossible based on contradictions such a proposition would create. (Burr / Goldinger 505-508) To present his argument, Hospers uses the example of traveling from January 1, 1962 A.D. to the year 3000 B.C.— the time at which the Egyptians built the Great Pyramids— and discusses several apparent contradictions within it.

The first contradiction Hospers identifies is simple: one can not be both in 20th century A.D. and in 30th century B.C. at the same time. He goes on to suppose that on one day, January 1, 1969, one is in the 20th century and that on January 2, 1969 one travels back in time to some day in 3000 BC. Here, also, Hospers finds a contradiction: "for the next day after January 1, 1969 is January 2 1969. The next day after Tuesday is Wednesday (this is analytic…) You may not live past January 1, but whether you do or don’t the next day (by definition) will be January 2." (Burr / Goldinger 506) While for Hospers it would be logically possible to find oneself in the environment of 20th century A.D. on one day and inexplicably in the environment of 30th Century B.C. the next, the day after today would still be tomorrow. Lest Hospers’ argument be taken for one of semantics, he reiterates:
When you say that it is logically possible for you (literally) to go back to 3000 BC and help build the pyramids, you are faced with the question: Did you help them build the pyramids or did you not? The first time it happened you did not: you weren’t there, you weren’t born… All you could say, then, would be that the second time it happened, you were there… But now we are speaking of two times, the first being 3000 BC and the second time being AD 1969. ((Burr / Goldinger 507)

Hopsers’ argument is a rational one. It matters not that time travel is as yet empirically impossible because even if one could experience being at one moment in 20th century A.D. and at the next 3000 B.C., reason would override any such sense experience as logically impossible. The argument rests on three premises: That one cannot exist simultaneously at two different points in time; that time by definition moves only forward; and that the past, having already happened, can not be changed (you can’t make what has happened not have happened). But what conclusion would one be led to make if any of Hopsers’ premises were shown to be in error or —to put it in the terms of the skeptic— how does one know that any of the three premises are true?

This question, "how does one know truth from falsity?" requires that a criterion or standard by which to judge the truth or falsity of a proposition be used. The sort of "global skepticism" employed by Sextus Empiricus in "The Problem of the Criterion" denies any such criterion is discoverable by virtue of circular reasoning. A.C. Grayling, on the other hand, provides an understanding of skepticism which identifies it as an epistemological tool rather than denial of any claims to knowledge. Grayling writes:
Scepticism defines one of the central problems in epistemology, namely, the need to demonstrate how knowledge is possible. This is done….by meeting the challenge to show that skeptical considerations do not after all defeat our best epistemic endeavors. …skepticism is best understood as a challenge, not as an agniological claim that we do or can know nothing…

This approach to skepticism is a sort of "scientific skepticism" which requires a solid, justifiable body of evidence to substantiate knowledge claims, rather than absolute certainty.

Returning to the question of time travel, let us look at each of Hospers’ premises under the discerning lens of skepticism. The first hypothesis then is: One cannot exist simultaneously at two different points in time. It is related to the second hypothesis, that time, by definition, moves only forward. In Hospers’ opening paragraph he warns that it is dangerous to assume that the same language that is meaningful in reference to space will be so meaningful in reference to time. It may be justifiable to believe that we can not exist simultaneously at two different points in space, but is this same assumption applicable in time-language? That depends on what exactly time is. On this point, the jury is still out. Albert Einstein described time simply as what a clock reads. Even if similar properties regarding location apply to time as to space, the property of spatial locality may be counter-intuitive. Bell’s Theorem provides evidence that once objects interact, however briefly, they remain connected even after they are pulled apart. Put simply, locality (the principle that an event in one place can not simultaneously effect an event in another place) is a non-reality — that distance in effect is an illusion and that everything and everyone is in one "place". Computer scientist James Culbertson has speculated that consciousness is in fact a relativistic feature of the space-time continuum. According to his theory, "Spacetime does not happen, it always exists. It is our brain that shows us a movie of matter evolving in time. …Special circuits in our brain create the impression of a time flow, of a time travel through the region of spacetime events connected to the brain." (Scaruffi, If the body of evidence bears out in favor of theories such as these, it may be not only possible to exist in different points in time simultaneously, but impossible not to.

Trefil’s "Guide to Pseudoscience," classifies ideas in three categories that he describes as being like concentric circles. In the "center" are universally accepted ideas which have a large body of evidence to support them. Beyond the center is the "frontier", which feeds new ideas to the center. Beyond the frontier lies the "fringe" containing ideas with little hard data to support them and where generally accepted scientific knowledge seems not to apply. The fringe does however supply ideas to the frontier and may be accepted provided the data to support them and/ or technology to investigate them becomes available. While Culbertson’s "spacetime" theory may still rest on the outer limits of the frontier it posits another hypothesis to guide the search for evidence.

The last premise of Hospers’ argument is perhaps his strongest. Hospers states: "This is an unchangeable fact: you can’t change the past. That is the crucial point: you can’t make what has happened not have happened." This indeed does appear to be a logical contradiction. To explore it let us look again at the example in the opening of this analysis, of the scenario in the film "The Butterfly Effect" in which the main character returns in time to events in his childhood and changes them. In Culbertson’s reality, spacetime events are static and ever-present. The flow or succession of time is much like an illusion, simply a way of ordering events. Our experience of these events hinges on our brain’s conscious connection to such events. Could it not be possible to forge a new connection to one of these events? In the film, Treborn’s time travel is achieved through a phenomenon of memory assimilation. By concentrating on journals he has kept of past events, he is able to literally (not figuratively) re-live these events, while retaining his present knowledge of the eventual outcome. Once a new choice has been made in one of these past events, his brain re-assimilates new memories of that event and all succeeding events (evidenced by scar tissue revealed on a CAT scan in one such timeline) thus forming a new timeline of events. Unlike Hospers’ example, where a change in past events indicates that the first time an event happened it happened one way, and the second time it happened a different way creating two different times, the scenario in the "The Butterfly Effect" gives a description of reality that is rather idealist in nature. It appears as if the character’s mind is the nature of his reality and by re-organizing the neural patterning in his brain he is able to manipulate that reality. For the idealist, the past would not necessarily be unchangeable.

In a more traditional or "central" view of spacetime and time-travel science, the conditions which would make time travel possible do not violate any accepted physical laws. Einstein’s theory of special relativity not only predicts that time travel to the future is possible, but indicates that reverse time-travel may also be possible through a sort of warping of the spacetime continuum, causing it to loop back on itself. A person or object able to travel along this loop would in essence be able to travel to a previous point in time. In this case Hospers’ final premise does cause a paradox, commonly referred to as "the grandfather paradox." Consider that you are able to go back in time and kill your grandfather before he has fathered your mother and consequently you are never born and can not travel back in time to kill your grandfather. Some, Hospers among them, would conjecture that because of this logical paradox, time-travel into the past is not possible.

There are, however, other theoretical answers to this paradox. One such idea is that the universe must have something like a law of continuity. This law would prevent a time traveler from changing the past. One may be able to travel to the time of the building of the pyramids, or the childhood of one’s grandfather, or one’s own childhood, but no changes to this past time could be made. This argument is shaky at best, because the simple fact that you are at an event in time that you were previously not in is in itself a "change." The other common response of proponents to time-travel is that one who travels to a past time was in fact there at that time, but was not aware that they were there until they traveled back. This type of solution to the paradox may be logical, but it is highly unlikely because it would necessitate the universe operating in some very unusual ways. This can’t be ruled out categorically, but since there is no evidence which would justify one’s belief in this unusual operation of the world around us, it would not be reasonable for one to assume its truth.

The conclusion on time-travel would seem to be, at this point in time, inconclusive. Carl Sagan summed it up by saying,
…maybe the joint effort of all those involved in this debate has at least increased the respectability of serious consideration of the possibility of time travel. … Of course we're not really at that stage; we don't know that time travel is even possible, and if it is, we certainly haven't developed the time machine. But it's a stunning fact that we have now reached a stage in our understanding of nature where this is even a bare possibility. ("Sagan on Time Travel",

Works Cited
Burr, John R. and Milton Goldinger. Philosophy and Contemporary Issues. New Jersey: Prentice Hall, 1996
Herbert, Nick. Interview with Dr. Jeffrey Mishlove "Consciousness and Quantum Reality with Nick Herbert, Ph.D". Thinking Allowed: Conversations On The Leading Edge Of Knowledge and Discovery With Dr. Jeffrey Mishlove. 1998
"Sagan on Time Travel".
Scaruffi, Piero. "Quantum Consciousness".
Kim Pfeifer <>

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