What is Time? Time is one of the most baffling concepts known to man. Augustine hit the problem square on the head when he proclaimed: “If someone asks me, I know. If I wish to explain it to someone who asks, I know not.” And later, we hear those sentiments echoed in the words of “theoretical physicist” Lee Smolin when he declares “[e]very schoolchild knows what time is,” but goes on for several pages to determine what this elementary concept entails. I offer no definition of time, and claim no more knowledge of the phenomenon than anyone else. In fact, I often find myself wondering if an objective time even exists.
The Fourth Dimension. It is curious when we think of time as the “fourth dimension” – as a realm we travel in. If time exists, we surely do travel in it – but always forwards. It is impossible to go backwards in time. Neither our physical bodies nor our minds (what is called “inner time”) can go backwards. I find this in sharp contrast with the other four dimensions. Depth requires us to be able to go forwards and back. Length – from side to side. Width – up and down. (These examples may change depending on the figure, of course). Even the fifth dimension – a tesseract or wormhole – presumes that we could go back through it. Time stands alone as the dimension we cannot go both ways with.
On a related yet unrelated note, I found myself wondering who first coined the term “fourth dimension” or presumed that this is what time was. The record is not immediately clear. The possibility of spaces with dimensions higher than three was first introduced by German mathematician Bernhard Riemann in his 1854 postdoctoral thesis, Über die Hypothesen welche der Geometrie zu Grunde liegen (“On the Hypotheses which underlie Geometry”), where he considered a point to be any sequence of coordinates (x, y, z, etc.). This opened up the possibility of geometry in higher dimensions, including, in particular, four dimensions. Believe it or not, this actually made physics easier rather than more complex. In 1880, British mathematician and science fiction author Charles H. Hinton published his essay What is the Fourth Dimension? in the Dublin University magazine. The term tesseract, referring to a four-dimensional cube, was coined by him.
Without Objects, Where Is Time? If every moving physical object disappeared, where would we find time? If space continued to exist, but without motion in it, time could not exist. The other ideas – length, width, etc. – would debatably still exist arbitrarily, although there would be nothing to measure. But time could not exist in this world, because time is always relative to something else – it is contingent on other properties.
Spritual Objects and Time. James Skemp raises the question of “spiritual objects” – what he calls “angels” or “ghosts”. They do not inhabit a physical realm, but are still objects in motion. Do they exist in time? I would suspect they must, as any conscious being would be able to have thoughts “before” or “after” other thoughts, or else there could be linear thought process. Without linear thought processes, there is no consciousness. And without consciousness or physical properties, the idea of something “existing” becomes so vague I dare not even tackle the concept.
Conventional Time Is Arbitrary. It seems obvious, but let’s just say it – any concept of time is arbitrary. Seconds, minutes, hours, days, years and so on are all inventions. There’s no good reason for one minute to have sixty seconds. There’s not even a great reason for a day to be twenty-four hours. It could have been twelve, or ten, or any other fragment we wanted to divide it up into. We wouldn’t even have to base it off of the Sun if we didn’t want to. Besides, different latitudes see different amounts of sun, do they not?
Our concept of a seven day week comes straight from the Bible, of course (God resting on the seventh day). But seven days is far from “the norm” historically. The Greeks had ten day weeks, the Romans had eight days. Even Soviet Russia in its infinite wisdom tried five and six days for a while, but changed back to the predominate seven days within a fairly short period of time.
Russia’s conception of time, including their long denial of the Gregorian calendar, is a whole topic in and of itself. But they are hardly the only ones reluctant to switch. A story this author is unable to confirm tells of the English rioting in 1752 shouting “Give us back our fourteen days” when the new calendar went into effect. This is hardly surprising given the problems, although presumably larger now, that would result today if we tried to switch again.
And even when we base our times off of natural events, we cannot do it to a degree of accuracy that will keep things constant. One year is 365 days. However, one revolution of the Earth around the Sun is actually 365 days, five hours, forty-eight minutes, and just less than forty-six seconds. Not even adding a leap day every four years (thank you, Julius Caesar) adequately corrects this difference in the long run.
Further Discussion on Years. While the difference between a calendar year and an actual solar revolution vary enough to differ in the long run, the idea of what a year is becomes even more confusing when one gets technical about it.
The year expressed in Section Four is the “solar” or “tropical” year (due to its being determined by our path around Sol, the Sun). But even those precise measurements are not exact. The forty-six seconds is closer to 45.51 seconds, with further decimal numbers to follow. And the more precise we are, the less likely we are to have that number as a constant (unless we truly believe the earth takes an identical path every year). The solar year is but one way to express the year.
Another way to express years is as a sidereal year, which runs closer to 365 days, six hours, nine minutes, and 9.54 seconds (with variances). This expresses “the time for the earth to make one complete revolution around the sun, relative to the fixed stars” and is slightly longer than the solar year.
Still another way would be the anomalistic year, clocking in around 365 days, six hours, thirteen minutes, and 53.1 seconds (again with variances). This version of the year expresses “the time of the earth’s revolution from perihelion to perihelion again.” The perihelion is the point where the Earth is closest to the Sun. Although the author is unclear as to how this would differ from the time taken from any one point to itself, this process is alleged to take longer than our standard solar year.
This, Too, Shall Pass. A thought both comforting and infinitely scary is the knowledge that everything passes in time and is ultimately destroyed. Every hardship we face will some day go away. We will overcome our obstacle or time shall do what it does best and wear down on whatever may stand in our way (while simultaneously wearing us down). As Tolkien so beautifully expressed in The Hobbit, time is the destroyer of mountains. Yet, we must not only look to the future for our troubles to pass but embrace the moment during our times of joy. Because every smile, every passionate kiss will also pass. And yes, ultimately, everything will die. No friendship, no matter how deep, can literally be forever. It is for this reason we must live each day to the fullest – for we never know when time will come for us.
Intervals and Epochs. When discussing time, it is important to remember that “time” is in reality two separate things: intervals and epochs. An interval is the time between two events. For example, when a runner asks “What’s my time?” he wants to know the elapsed minutes and seconds between the moment the gun went off and the moment he touched the tape at the end of the track.
An epoch is an exact event — a fixed point in time. When someone asks “What time is it?” or “When did Columbus reach America?” they want to know a specific time or date, and this time is called an epoch.
The relevance of this is that when we discuss the nature of time, and whether or not time exists, we must recall that there are really two ways to look at time. Someone could argue there are intervals between events, but there are no epochs (in the sense that to pinpoint something exactly would take an infinite amount of measurement — see Section 26). So when Augustine asked “What is time?” let us be sure to be talking about the same thing.
Thoth, Chronos and P’an Ku. Many cultures created gods for various situations. And two of them (in fact, many more than two) created gods to symbolize time. While this has little philosophical relevance, it is interesting to throw this in anyway.
Thoth, the Egyptian god of time, is probably not well known to many of us. He devised the Egyptian calendar, for which he was honored by having the first month named after him. Incidentally, he was also in charge of “weighing the souls” of the dead, seeing who had earned passage into the timeless afterworld.
The Greek god Chronos, also known as Father Time, is probably more familiar to those who have taken any interest in Greek myth (as most of us have at some point in time). He carried a sickle for cutting away the years, and is now often shown in cartoons as the symbolic end of each year (in contrast with a baby symbolizing the new year). Both the baby and the old man are Father Time, who ages a lifetime within one calendar year – infinitely.
Known to none of us is the Chinese god P’an Ku. He was said to have created time when he carved the heavens out of a “cliff of chaos.”
The real philosophical issue comes into play when we ask what was before the creation of time by these gods, or who managed it before them? Does the word “before” even mean anything? If they existed “outside” of time, what does that mean? We can ask these questions of our own Christian god, as well.
Drugs And Time. It is no secret that drugs – almost all drugs – have an effect on how individuals perceive time duration. Anyone who has been high on marijuana has noticed that a 3-minute Beach Boys song becomes an elaborate rock ballad. A 17-minute rock anthem like “Inna Gadda Da Vida” becomes an entire Broadway musical. Studies have confirmed that marijuana, hashish, and opium slow time down considerably for the user.
On the contrary, caffeine and amphetamines (“speed”, “crank”, “meth”, etc.) tend to speed time up for those who use these drugs. Time not only goes faster, but so does the individual. A half hour will seem like fifteen minutes, but with the extra energy they will have accomplished what would normally be done in forty-five minutes. I find that reading is a fine example in my case. In a “sober” state I tend to read twenty pages in an hour. With higher levels of caffeine I can take down about sixty pages (or more if I am reading something a little less dense than usual).
Alcohol and Time. I quote a young man from the beautiful state of Maine: “One of my favorite phenomenons of time is the drunken black-out. Once I went to a party by the bay and the next thing I knew I was weaving down the road back to my room, wet and covered in sand and sans glasses. I never did find those glasses. And many times I have simply lost whole hours, whole nights to black-outs. It is interesting to attempt to reconstruct a night, either by looking at dirty dishes and broken furniture, or by hearing the testimony of others. Of course, this is more a phenomenon of alcohol than it is of time.”
Dreams And Time. It is an incredible thing to notice what sort of effect dreams will put on our perceptions of time. A dream that lasts fifteen minutes in “awake time” (if a scientist is monitoring the dreamer’s brain waves, for example) may actually seem like hours or days to the dreamer. An entire plot is developed and carried out during even the most brief nap. What is perhaps even more strange is our body’s ability to adjust back and forth between these two states. When we awake, we do not find ourselves wondering what day it is – we look at the clock and fully accept that it has been a mere four hours (or more if you are not like me).
A theory I have not personally experienced is that time does not exist in dreams. Time as in manmade time, that is. My colleague Jason Lane has relayed this to me, as has the film “Waking Life” (lent to me by James Skemp). The idea is this: if the dreamer looks at a clock or watch in the course of dreaming, the face will appear blurry. No matter how hard he (or she) tries, there will be no concept of an exact time. This is not to say there isn’t a vague sense of time. Obviously this condition can exist if we are to believe the frequency with which people dream of being late for math tests.
The Moon and Women. There has long been a rumor that women’s 28-day menstrual cycles are in some way related to the moon’s similar cycle. (The word “menstrual” does, of course, come from the Latin word “menses” – related to the word “month”, which derives directly from the term “moon”.) As near as I can tell, these similar timespans are merely coincidental. The same people who believe in this connection (Samuel A. Goudsmit and Robert Claiborne, among others) are the same who have written: “What seems to be a multiple lunar cycle shows up in the 120-day average lifetime of blood cells.” Because four months average out to 120 days does not definately signify a connection in my mind.
Circadian Cycles. A circadian cycle is a routine that is based on the idea of a (roughly) twenty-four hour day. Circadian means, literally, “about a day” (from the Latin “circa dies”). It is amazing how with or without sunlight plants and animals respond physically to these cycles. Plants know when to open and close their buds. The human body speeds up and slows down at a set time (even third shift people who have forced their bodies to go against nature are still involuntarily functioning at a higher level during their sleep than while at work).
In 1938, Nathaniel Kleitman and Bruce Richardson entered Mammoth Cave for 32 days with the intentions of switching to a 28-hour day. They tried 19 hours of being awake and nine hours of sleep. Richardson’s biological clock had adjusted within a week. Kleitman, who was twenty years older, was unable to escape the 24-hour cycle. This experiment shows – or at least supports the idea – that our bodies are not naturally on 24-hour cycles because of nature, but more so out of habit and could be changed to fit other environments if done at an early enough age.
The pineal gland, which Descartes believed was the seat of the soul, runs on an apparent circadian cycle. It secretes at regular intervals. One of the first occurrences observed regarding this involved the sexual cycle of female rats. Perhaps there are many more? This same gland, according to trepanation fanatics, increases our mental abilities when exposed to more light – signifying another connection to day and night cycles?
Jet Lag. Our body’s reliance on the Sun for keeping “correct” time is shown best with jet lag (and related physiological symptoms). When we land in another state or country expecting it to be 5:00 and its already 8:00 we are thrown off by this little bit for several hours and often times won’t even adjust at all until at least the next morning. Is it the Sun’s position in the sky that confuses us or the manmade time that tells us a time we “know” isn’t in keeping with our internal clock?
To some extent, we could even say this happens at daylight savings time (a phenomenon I believe should be abolished). Most of us are asleep at the time, so we transition rather smoothly – maybe suffering nothing more than a lack of one hour’s sleep. But those of us who are awake are thrown off for a while. On a similar note, how many of us are asking other people constantly for the next week if the clock is right? Each store we visit, each classroom – “is that right?” More a funny little detail of life, but still worth mentioning.
Stonehenge. Someone spent way too much time and work to develop this monument if it truly is nothing more than a giant clock. I cannot deny that it adequately lines up with both the winter and summer solstices – but is that all? Moving literally tons of rock for that?
For all I know they did it for an entirely different reason – to confuse the piss out of scientists for hundreds of years and fuel the imaginations of young pagans. While I have lost no sleep over it, I would be lying if I said that Stonehenge doesn’t seem to be a rather fascinating device and not just some punk kid’s pet project.
A Very Brief History of Clocks. The history of clocks is less a story of technological development and more a story of competitions in foreign lands. A “water clock” (which many would regard as the first true clock) was invented in 1088 by a Chinese mandarin named Su Sung under instruction from the Emperor. This amazing invention not only told the time of day, but also the date, month, and a variety of other things. At this time in history, Europe was in the throes of the so-called Dark Ages just waiting for Thomas Aquinas to straighten everything out.
It wasn’t until almost six hundred years later that the Europeans made a significant advancement in the field. In 1656, Dutch physicist and astronomer Christian Huygens (1629 – 1695) patents the first working pendulum clock. Up until this time, measurements could only be accurate in ten minute spans, but Huygens was able to get the span done to near ten seconds. Much to the dismay of this author, the idea took off and clocks became disgustingly popular. Today, we have made them a necessary evil in our everyday lives.
On a completely unrelated note, the international time zones were established in 1883, to make sure that Dutchmen were safely asleep while the Chinese were out inventing their next momentous creation.
The Origin of the Universe. Trying to ascertain the beginning of the universe is no small task. We as human beings have been wondering about this since we first walked on hind legs. Let us assume for the moment the Big Bang is true, or at least our closest current theory to the truth.
Like the gods mentioned above, we are plagued with the question of “what came before.” Was it God? Did the universe sit in a condensed state for a near-eternity just waiting to go “bang”? Or has the universe been repeatedly expanding and contracting forever, each time recreating itself and life – possibly even our same lives – springing anew each time?
If all this is eternal (as I like to believe), how is it we get these dates of creation (currently ranging around ten to fifteen billion years ago)? Matter clearly existed before the “bang” so how can we say at what point it “began”? While I am sure any freshman level physics major could answer this, I do not happen to be one of those.
Relativity. When Einstein gave us the theory of relativity, what he essentially did was transform the mild-mannered simple idea of time into a hulking behemoth of confusion and insanity.
Very simply, relativity tells us that time slows down at high speeds (as we near the speed of light) and for this reason time is not absolute. We could get in a spaceship and travel at half the speed of light (which is impossible, but work with me here) for a few years. When we come back to Earth, we find that hundreds of their years have passed and we are the same age as our great-grandchildren. While I know this to be true, to try to comprehend it with the human mind is a nerve-racking experience.
Science fiction fans will note that Dana Scully from the television show The X-Files once remarked that time is a “universal invariant”. This is incorrect. More surprisingly, true devotees of the show will know that she was once a physics student who wrote her undergraduate thesis on “A New Interpretation of Einstein’s Twin Paradox”. If Scully couldn’t even correctly recall the basics of her studies, what are we to make of her as the “straight” thinker on the show? But this is all unimportant…
Nikolai Berdyaev. Berdyaev said some stuff about time, but damned if I know what it was.
Entropy and the End of Time. Entropy is a theory that was first devised by Rudolph Clausius (1822-1888) and is now known as the Second Law of Thermodynamics. Quite simply it states that any system left to itself will become more disorganized and chaotic. (It is interesting to note that evolution directly contradicts this, relying on a lesser known principle called negentropy.) This phenomenon is easily visible – things will always break down over time (such as cars), and never do they become fixed or more complex without the aid of some outside force (a mechanic, whose body is breaking down as he fixes the car!)
The Austrian physicist Ludwig Boltzmann (1844-1906) has said that the “end of time” will be when the universe reaches maximum entropy. When maximum entropy is reached, no more changes can occur – and without change, there is no time. If Boltzmann has done his math correctly, this event should happen in about 10,000 billion billion years.
But what if we reverse this idea? If things are always becoming less complex, it should stand to reason that the farther back in time we go the more complex things are. While this is true with cars and other manmade objects, it seems unlikely that life was more complex several million years ago than it is now. And if time has no beginning, it would have to be infinitely more complex as we go back in time, which seems absurd.
Entering During the Third Act. I believe Kierkegaard was the one who said we are entering life in the third act. An example runs as follows:
You are late for your movie, “A Walk to Remember”, because your girlfriend took too long in the bathroom again. As you enter the theater, you meet the Mandy Moore character and meet the Shane West character shortly thereafter. However, you missed the opening sequence explaining Shane’s past and his tendency towards delinquency. Regardless, you are able to determine what happened and pick up from where you started just the same with minimal adjustment.
Life works exactly the same way. We enter life during the Third Act. Humanity has been performing this comedy for a million years, and we only get to watch a few decades of it – if we’re lucky. We blend in perfectly without all the first-hand knowledge of what came before us. We don’t know Winston Churchill’s favorite breakfast cereal. We don’t know of Jesus’ girlfriends in his teenage years (we only know of his last three years on Earth, those twenty-five or so in between are a complete mystery). But we make the most of what we have, and everything works out. That is the power of inference.
The Dangers of History. By now, we are well-acquainted with the truism that history is written by the winners. We must be ever mindful of this when we take into account paragraph 19. We cannot be sure of anything before our time, as we rely solely on the winners of the past. Our ethnocentric views and patriotism get in the way of history. Even religion is ultimately skewed. Had the Crusades gone differently, our views of Muslims would be much different today. And what of the Gnostics whose gospels were banished by the Church? There is little evidence that our four “canonical” gospels hold any more truth than any of the other contemporary gospels, but we accept them as fact because the Church “won” by silencing others. Taken back a step – what if the Romans had kept the Christians down entirely? Jesus would be but a footnote, not a way of life. It is important to note that other great truism – what is popular is not always right, and what is right is not always popular.
Hitler on Time. Hitler’s concern with time was less with the physics or metaphysics of the concept, and more with the pure aesthetics of it. I quote him at length, as I think he says perfectly what I could only repeat in a paler vein.
“Go to a theater performance and witness a play at three o’clock in the afternoon and the same play with the same actors at eight at night, and you will be amazed at the difference in effect and impression. A man with fine feelings and the power to achieve clarity with regard to this mood will be able to establish at once that the impression made by the performance at three in the afternoon is not as great as that made in the evening. The same applies even to a movie. This is important because in the theater it might be said that perhaps the actor does not take as much pains in the afternoon than at nine in the evening. No, the time itself exerts a definite effect, just as the hall does on me.”
The practicality of this principle is important for both artists and politicians alike. Perhaps there might even be a change in people’s response to various television programs depending on when they are aired. Are “The Smurfs” or “Perfect Strangers” more agreeable in the morning or in the evening?
Children’s Mastering of Time. According to anthropologist Edward Hall (1914-), a “well-known authority of children in the United States” (whom he declines to name) has determined the average child masters time in about twelve years. By mastering time, we mean that he or she has a sense of what time is and how to live in conjunction with this thing. Younger children will only be able to grasp concepts such as “a little while” and then even in varying degrees. Older children who fully understand minutes and hours in a formal sense most likely still will not be able to use them in any practical way until these concepts become internal (and hence, informal).
We might wonder if time is internal to begin with and we must then learn to use it for our own ends, or if time is wholly external (or manmade) and we thereby internalize it once we realize its necessity in the world. Cultures that do not rely on formal schedules never internalize minutes or hours, but even they have an internal time they are aware of for planting crops or other activities which are time-specific. I believe time is internal much the same as space is. Children will grasp time and space similarly, if we take into account how much better sense the idea of a mile is to an adult than a child. But miles, too, are set measurements of man. So this does not fully answer to what level (if any) time or space are natural for us.
Midnight or 12:01? Some debate has been made between whether a.m. and p.m. switch at the noon and midnight points, or the minute following. By extension, the beginning of each new day is debatable by a full minute.
In common usage, we accept midnight as the beginning of a new day, as evidenced by our alarm clocks switching the a.m./p.m. light at this point and our general agreement that midnight is a.m. But sometimes midnight is seen as p.m. and 12:01 becomes the a.m. (which may sound confusing, but makes just as much sense if not more when we think about it).
This warrants further investigation as to why people accept two different time constructs, but for now I do not have the materials to properly do this.
Arabs and the Future. While American culture relies heavily on schedules and due dates, not all cultures do. In fact, the Arab world explicitly forbids the idea of the future being a foreseeable occurrence. Edward Hall informs us that “the Arabs regard anyone who tries to look into the future as slightly insane.” He uses crop yields as an example – while Americans presume they can estimate their annual production of corn or some other crop, an Arab would not venture any such guess under the pretext that only Allah could possibly know what lies in store for them.
The Promptness of Mormons. Edward Hall claims that Mormons (and by extension, Utah) is on a schedule that makes even lateness of a minute or two a complete insult. Elsewhere in this country, being a few minutes late is hardly considered unusual and often times makes more sense in situations where we know full well we would have had to wait those extra minutes for the person we were meeting in the first place.
Displaced Points and Diffused Points. Two methods of timeliness have been established in the Western world. When I tell someone to meet me at 6:00, the time they arrive will depend on whether they work on diffused time or displaced time. Unless they are a woman, in which case I should be happy if they show up by 7:00. Those acting on displaced point might arrive as early as 5:30 and most likely no later than 5:57, as they see time as set and promptness as important. Diffused point people will arrive anywhere between 5:50 and 6:10, seeing time as a range, or interpreting my 6:00 as “6ish” and working from there. A person is easily identified as one or the other because they will not switch from one point of view to another at random and there is very little overlap between the two groups (5:50-5:57, or 7 minutes overlap out of 40 minutes of variations).
Do Moments Exist? Gustav Bergmann, an analytic philosopher writing in the 1950s, alerts me to the debate of whether or not “moments” exist. According to Bergmann’s Meaning and Existence, “Every relativist holds that moments do not exist. All relativists except [Leibniz] hold that (some) temporal relations do exist and that no nonrelational temporal character does… Some absolutists … may hold that only moments exist.”
Bergmann goes on to explain what “exist” means in philosophical language, a discussion that is largely unimportant (though interesting) for the sake of this debate. We can say unicorns “exist” because we can speak of them and hold them as a concept, though we know unicorns do not likely exist in any real sense. What of moments? Do they exist outside of our abstract ability to talk about them? The debate runs as follows: on one hand, we should accept moments because we are able to say that something happened before or after a precise time (a moment). Yet, if we pick out what we would call a moment — say, a second — we can divide it even further (into nanoseconds), and those segments can be divided even further. Any moment would, in fact, be an infinite amount of smaller pieces and not actually one concrete thing at all.
Moments are like (extensionless) points on a line. Any point can likewise be divided up into still smaller lengths. Thus, absolutists accept moments and points, on the grounds that in order for things to be linear (have before and after) they must be able to be broken up into various segments, called moments. Yet, the relativists would favor the idea that a moment is not an instant and therefore not able to be concretely nailed down. The relativist accepts that an apple becomes a core after it is eaten, but does not think there is a defined moment for the switch — only a relative position of one to the other.
Do moments exist? Are they figments of our imagination? Or is this all simply a semantics game?
Is the Past Verifiable? Bergmann also asks if we can ever truly verify the past. He concludes that, “Statements about the past cannot be directly verified”, yet claims, “Statements about the past can be verified indirectly.” How does he come to this?
If we accept the empiricist’s viewpoint, something can only be true and verifiable if observable by the senses. We cannot view the future, nor can we view the past. We can only view the present. We can ask, “Is this apple red?” and answer “Yes, it is red.” But when asked, “Was this apple red yesterday?” we can say “yes”, but only when we appeal to non-sensory information. Perhaps we saw the apple and rely on our memories. Perhaps we know this apple is ripe, and given what we know about apples can deduce that it has been for some time and was thus ripe (red) yesterday. The more something fades to the past, the more difficult it becomes to verify, as we rely on more and more indirect methods.
Memories fade, history books may be biased or inaccurate. Scientific methods of dating may tell us some things about the past, but only so much. Once the present has passed (as it does continuously), the verifiability of things becomes increasingly more difficult. This is not to say that we can’t trust our knowledge of the past, but we must be aware that there is no direct way to empirically verify anything outside of the present. This is one of the great problems of not only time, but epistemology in general.
Stephen Hawking on Time Travel. Lawrence Krauss sums up Hawking’s view that time travel is impossible: if it could ever be done, “we would be inundated by tourists from the future”. This is absolutely correct, assuming the travels through time do not go to parallel dimensions. Yet, even if they did, this would make time travel relatively pointless: it would affect the world of the traveler, but not of anyone else, as we would still be living in the unchanged universe…
Deja Vu and Fortune Telling. Most people probably do not think of deja vu or fortune telling as “time travel”, but in a sense they are. Shirley MacLaine wrote in Out on a Limb that deja vu was “an overlap of a future-life experience”. Or, as Krauss says, “Seeing into the future means that in a sense the future has already happened.” We would have to presuppose that the future is determined and that we could either send our thoughts forward or future sights would be traveling backward… a very strange thought. And if we see future events, what is to stop us from changing them, thus making them not determined… it’s a bit of a mess. (Luckily, fortune telling is largely discredited, so we can ignore the problems this creates… and the science on deja vu is interesting and still being examined. Perhaps I shall expand on this in the future.)
Time Travel, the Movies, and Paradox. Anyone who has seen movies that involve time travel and put thought into them has probably thought to themselves that there are some serious flaws in the way the plot unravels. There are countless examples, and more that come out all the time. Websites have been devoted to chronicling this problem. Krauss points out two of the bigger film franchises, and they deserve to be mentioned: The Terminator and Back to the Future. Now, of course, we have to suspend disbelief to enjoy these films, but let’s be frank: they do not hold water.
Assume the Terminator is sent back in time to eliminate Sarah Connor. If he succeeds, there will be no reason to create him, and then he could not have been sent back to kill her. (We might argue that this time loop works if he does not kill her, but if in the future they know this, why even try?) Or assume that Biff Tannen became rich by bringing a sports almanac back from the future. Had he done this, he never would have been the schmuck in the future who traveled back!
Counter-Example: 12 Monkeys. Spoiler warning for those who haven’t seen it, but 12 Monkeys is a great example of a closed-loop time travel, and more likely how things would happen in real life if time travel were possible. Krauss: “At one point, the Bruce Willis character, who has traveled back in time, tells someone that there’s no need to worry about his presence in the time frame, because a time traveler cannot change history. Indeed, the Willis character’s death in the movie is a classic example of a closed timelike curve.” I believe that Timecrimes and Triangle would also fit this example.
Krauss, Lawrence Maxwell. Beyond Star Trek: Physics From Alien Invasions to the End of Time. BasicBooks, 1997.