The author is known for, among other things, his web site Temporal Anomalies in Popular Time Travel Movies, and its exposition and defense of the Replacement Theory of time travel. In this article he explores the possibility of an alternate theory of time. The article is presented here at Gaming Outpost for comment and discussion, with the expectation that it will be added to that web site after a reasonable period for comment.
Many have written to me mentioning Poul Anderson’s Time Patrol stories, and I have written back to say first that I had not read them and second that I did not do analyses of books for a variety of reasons. This past year, though (2008), one of my readers decided to mail me a copy of the complete collected stories, along with some other science fiction and fantasy books he thought would round out my familiarity with the literary side of the genre (and I did and still do thank him for that). I read it, and would say that to some degree I enjoyed it; they are good stories well told. They do not, however, fit into any model of time travel familiar to me.
This led me to wonder whether there was a plausible model of time travel I had missed. I long pondered what sort of description of time might make Anderson’s stories plausible, and began to tinker with a model I am presenting here. I still will not analyze books, and am not going to do so here. I merely wondered whether the Time Patrol stories might become possible with a different model, whether Anderson actually had a clear, coherent, and plausible theory of time and time travel from which he was working, and whether I could discover it. This is not, then, an analysis of those stories, but only an effort to develop an alternate conception of time in which stories like those, if not those stories, might be conceptually possible.
Model Failure
In Anderson’s world, people travel to the past all the time–but most of them do so because they work for an organization dedicated to preventing changes to the past. It seems that the day people, somewhere in our future, discovered time travel, they were visited by people from a yet much more distant future, an incomprehensibly distant future, who had a vested interest in preventing change to the past, and so informed those earliest inventors of the technology that they were now drafted into a temporal police force to prevent anyone else from using their technology to change the world. They also recruited at least a few people from earlier times, including several from the twentieth century, to work as researchers, historians, and enforcers. These were provided with the equipment needed to travel through time, and given life extension therapy so that others from their own age would not wonder either why they aged so quickly or where they were all the time.
Even a causal reader of this site should recognize that such a scenario is not possible under any of the familiar models of time. Bear with a brief exposition of the flaws.
Under fixed time, perhaps the most popular model of time travel, the people in the future are wasting their efforts trying to preserve the past, because the past cannot be changed–all effects of all time travel events are already part of history, and those who will at some point in the future travel to the past in some sense have already done so, have already arrived in the past. The time patrol itself is nonsense, as it is enforcing rules that cannot be broken by attempting to break them. One might was well organize a police force to enforce gravity, and say that in their efforts to enforce the law of gravity they are permitted to break it. Of course, Anderson’s stories would be rather boring in that case. That’s not to say that you can’t tell an interesting story in fixed time–only that a story about a police force that attempts to correct changes made to history before they become serious problems is not such a story.
Parallel and divergent dimension theory is vexed by the problems outlined in The Two Brothers: Why Parallel Dimension Theory Is Not Time Travel. Notably, our future society that is attempting to preserve itself is simply creating other universes. As with fixed time, the society of the future cannot be changed–in this case, because its history is fixed, and the time traveler is tampering with someone else’s history. Further, if we assume that someone from the future has traveled to the past and created a new universe in which that future society does not exist, then someone else from that future “fixes” the universe such that that society is restored, we have gone from having one universe in which that future society exists to having three universes–one in which the future society existed and was never endangered, one in which the future society never existed and never would have come into existence, and one in which the future society came into existence because after a traveler from the future tampered with history, someone else tampered with history again.
Even more problematic for telling such tales under the parallel/divergent dimensions theory is the problem created by the linear nature of each such dimension. Although Back to the Future Part II is a disaster of a time travel story, it gets this part right: once Doc and Marty are in a divergent dimension, they cannot go forward to the point from which the time traveler departed to correct the problem, but only backward to the root where the change occurred. Once a change has been made in the past that would destroy the society of the future, there is no society in that future who can detect and correct this. In that dimension, that society never came into existence.
The replacement theory–the theory supported by this site–also rejects such a concept. For there to be any future universe, all anomalies must already have resolved. Let us suppose that the future society lives in twenty thousand A.D.; let us suppose that time travel is discovered in three thousand A.D. If our time travelers in three thousand travel to two thousand and completely alter history between two thousand and three thousand, maybe they will destroy time, and maybe they will be very lucky and preserve time–but by twenty thousand, that’s all ancient history, more ancient to them than the earliest Egyptian inscriptions are to us. Whatever that society is, it became that because of whatever changes were made to history by all time travelers before then. Their intervention cannot prevent settled history from changing, because for them the changed version is and has always been the settled version. They exist because of every change that was made, not in spite of these. There is, again, nothing to protect.
Yet the stories seem plausible. It suggests that there is a way of understanding time that does not fit any of these models.
Dimensionality
The solution that seems to be in view is to perceive time in two dimensions.
On one level, this is similar to the conception of time outlined in The Spreadsheet Illustration of Temporal Anomalies–similar enough that the reader should understand that concept before attempting to grasp this one. In short, there is a sense in which all of history occurs metaphysically simultaneously. The future is not unformed, merely undiscovered; the past is not unalterable, merely known. If there is a change in 2000, there is a consequent change in 3000, an immediate change because the events in 3000 are in direct causal dependency upon the events of 2000. It does not take a thousand years for the change to occur; it takes a thousand years for us to reach the place in time where the change occurs.
Each of the popular theories of time travel treats this problem differently, but in each case it can be comprehended by visualizing time as if it were space. In the fixed time theory, that space is unidimensional: time exists in a continuous line from the past to the future, and cannot be altered. With the parallel and divergent dimension theories, there are multiple timelines lying alongside each other, and travelers leaving one arrive in another. This is the concept of sideways time, suggested in a John Pertwee Dr. Who episode and exploited in Sliders. In this conception, these parallel or divergent universes exist temporally “alongside” each other, but are disconnected save by the acts of time travelers, who are really dimension hoppers. Also, the past is immutable, but the future is being created.
The replacement theory gives the impression of two-dimensional time, but it does not support the conception. Rather, as with fixed time, it maintains that there is only one history of the world–but that it might be altered, and if it is then there is still only one history of the world, the other having existed only in some metaphysical past, something like the program on your video recorder that you erased to record another. Still, the description of history in this case involves tracing causal lines to determine whether the past still supports the future which supports the past. The past can be changed, but once it is, nothing from the original past remains.
For Time Patrol to work, there needs to be two-dimensional time. Time moves from the past to the future, as is familiar to all of us; but it also moves laterally, from one version of history to another. Yet lateral versions of history still exist, and anything which originated in one can continue to exist in another.
Fixed and Fluid
What ought to make this work is the interaction between chronological time and lateral time. Having accepted that chronological history all exists simultaneously, and that time is merely the way we experience it, we can understand that a change in 2000 could cause an immediate change in twenty thousand. We would have to wait until we reached twenty thousand to see that change, but there are people in twenty thousand whose lives would change immediately.
The problem is, no one in twenty thousand would know that history had changed. It would always have been thus–unless there is another aspect to time.
That other aspect would be the lateral. This rests on the notion that change requires a medium within which to occur. In history, change occurs through chronological time: I drop my pen now, and it hits the floor now. We are accepting that this is perception, that the falling and landing of the pen are accomplished instantaneously in various points in time. Yet if we involve time travel, and we eliminate at least some of the conception of time as the medium in which changes occur (because we are now looking at global changes, changes which occur instantly across all of time), it might be asked how that change can happen. The answer then is lateral time. With each tick of lateral time, the history of the universe is established; if a time traveler from a previous tick makes a change to the past of this one, the entire history of this tick forms to accommodate that change, but still accommodates causes which have moved from the previous tick into this one.
That means that time is not really moving “forward” toward the end of history, but it is really moving “sideways” from iteration to iteration of all of history. Anyone who moves backward in time also moves sideways, into a subsequent iteration of the entire history of the world. He might undo his own birth, but this paradox is inconsequential, since his birth still exists in the iteration of history from which he came, a spatio-temporal location as real yet inaccessible to him as yesterday is to us.
The Disappointment
Unfortunately, this does not solve the notions promulgated in Anderson’s work.
As noted in connection with parallel and divergent dimension theory, the problem still remains that in any iteration of history in which the desired future society is destroyed, it does not exist. Thus it cannot send enforcers back to correct a problem that it cannot detect.
Anderson’s answer to this seems plausible on its face. Time Patrol training facilities exist in an era in the distant past–prehistoric past, dinosaur past. This facility includes among its resources everything that is known about the future history of the world, and specifically what events are thought to be important in establishing the existence of the future society which sponsors their work. Since this facility exists at a point prior to any known ventures to the past, it continues to exist despite changes made in its future. Since it can still possess information and personnel and equipment which were delivered from the future of one iteration of time, the shifts in the existence of the future society will not impact its ability to perform its mission.
The problem is finding the relationship between historic time and lateral time. Think of it this way: those who are stationed in the past are charged with preserving the future whose records they have in their files. The moment some change in that future is detected, one of their own must undertake to identify the change, determine how to restore what would be as near as possible to the original history, and travel to whatever point in time this repair can be implemented. But it is that aspect of knowing when the future has been changed.
From the perspective of historic time, the answer seems to be either that it will be changed or it will not be changed at a particular moment. Our theory of two-dimensional time, though, suggests that there is an original history of the universe in which no time travel events ever occurred, and then “when” someone traveled to the past, we moved laterally across time to the altered history. That lateral shift, though, is not something we can perceive or experience; it also is not something that happens at a specific moment in the historic timeline: it happens to all of history simultaneously. Thus at time L1, the original history of the world, no one can detect any change in history. Then at time L2, following the “first” time travel event, everyone who can detect such events detects that one simultaneously.
To clarify, let us suppose that the time patrol base in the past exists for a thousand years. In the L1 moment, no one ever detected any change in the history of the world. Then as we moved to the L2 moment, a change occurred. That change became detectable–but it was detectable simultaneously through every second of those thousand years. Then the L3 moment occurs, due to another trip through time, and both changes are detectable for that entire thousand years. More significantly, those who live in the time patrol base when it reaches L3 cannot know which of the two detected anomalies occurred first. Further, those who live at year 1 have no means of knowing whether they are actually detecting a change made by their own people at year 5. In fact, every time someone is sent back to the base, it creates a detectable anomaly, a change in the history of the world, a next tick on the lateral timeline. Without a complete roster of everyone who was recruited and sent for training, the people at year 1 cannot sort out who is what.
You might think it a simple enough matter for the people at year 1000 to send a that complete roster to the people at year 1, so that they can use that to compare against whatever they detect. The problem is, as time moves laterally the information at year 1000 will change but the information already sent to year 1 will not–otherwise, the record of the history of the future society these people are trying to preserve would also change, and they could not know whether history had changed or not, or what it was they were trying to preserve. In order for the people at year 1 to have current information, the people at year 1000 must send back an update with ever click of lateral time. That, though, is impossible. Even were we to suppose that our time travelers have a way of detecting clicks of lateral time, they cannot act in lateral time, only in linear time. They can send a roster back from the earliest lateral moment in which they have that roster, but in order to send an updated roster they would have to be able to send both rosters simultaneously. Again, if we assume that having sent the one roster at L1 they automatically will have sent the most currently updated roster at L1000, we must also assume that whatever history of the world was sent back from the distant future is that version that exists at L1000, having been updated by virtue of the fact that the people in that future will have sent the most current version.
Too, this ignores the detail that the very sending of the current roster is itself an event, a change to history which needs to be recorded on the roster of those events which are to be ignored.
The concept of lateral time does not solve the problems created by the Time Patrol stories, nor does it appear to resolve any other problems. My impression is that the replacement theory is still the best theory. However, I offer this as a starting point for any readers who think there might be something of value here, and invite you to make your suggestions for how this might be brought to a functional theory of time. I am available by e-mail, but would prefer to have such discussions publicly, and so invite anyone interested in posting at the official Multiverser forum at Gaming Outpost, where there are at least a few persons interested in such discussions.
May 3rd, 2009 at 11:13 am
I read some of this. I stopped when my brain started to bubble, and am now letting it cool off by imbibing large quantities of vanilla ice cream, and watching kids’ cartoons. Not really.
I’ll be back to it later.
The idea of lateral time is used in ‘Arc Riders of the Fourth Rome’ which is also time travel. One of the members of the travel team is a lady who was born in a timeline that no longer exists.
The problem of genocide with lateral time is what prompted me to come up with the I Forget the Name Right Now, but its a Thirteen-sided Time War. In that particular dimension, people are Broad (We are Narrow) in their Lateral Time Sense. A person is a function of Potential Temporal Energy which gets expressed in Actual Events. Its sorta like Schrodinger’s Cat except there are a lot more possibilities than just two.
And with this, as you move in lateral time, you don’t commit genocide because the same people still exist, but their expression is different.
May 3rd, 2009 at 11:15 am
The 13-sided time war is a Multiverser world that I playtested for Ed. It had its problems.
May 3rd, 2009 at 10:57 pm
Ah, Schroedinger’s Cat.
Did you know that Schroedinger created that particular thought experiment to demonstrate that the multiple dimensions theory was utter nonsense, and now it is cited to explain how the multiple dimensions theory works? If the explanation means what the person who wrote the explanation meant by it, then the explanation is that it doesn’t work.
But this is fiction, of course, so it’s allowed to work in some universes.
What I have most trouble with, I think, is the notion that just because a theory of time is complete irrational nonsense doesn’t mean it can’t be true in some universe.
What I’m trying to do here, though, is devise a theory that is not complete irrational nonsense which makes possible some kinds of time travel stories that are not possible under the existing theories. I don’t believe I have as yet suceeded, though.
–M. J. Young
May 18th, 2009 at 11:46 am
I think, the problem with the above theory is that it does not treat lateral time as a truly temporal dimension. The idea is to treat lateral time vs. time as time vs. space. We do not see changes made in some place instantaneously affect the entire space. In fact, relativity tells us nothing is affected at all beyond the boundary that light can reach within elapsed time. Similarly, changes made at a particular instant of time do not spread across the entire timeline in one lateral click. By the way, lateral clicks happen with or without time travel, and timeline is being refreshed across the entire stretch due to quantum wave functions collapsing into different states.
As a consequence, chronological history does not exist ‘simultaneously’ but is created at a fixed rate (one year of time per one unit of lateral time equal to say 10^30 clicks). There is no single present, each instant of time is recreated at each click of lateral time across the entire timeline. Once that instant is recreated its previous version is lost ‘forever’, but not before it creates a latter (in time) instant of a latter (in lateral time) timeline. Both the past and the future are mutable due to random events with changing outcomes, or due to deliberate changes made by time travelers.
But changes do not spread across the entire timeline ‘instantly’, they propagate through time at the same rate as we live through it. For example, changes made in 2000 would only spread up to 2030 after 30 units of lateral time. In particular, without time travel we would never become aware of changes made to our past or, for that matter, to our future. Also, there is a detectable moment at which the changes are made, they do not happen to all history ‘simultaneously’.
In this picture, Anderson’s future time travelers have nothing to worry about. Even if their past is erased they will never be affected by changes spreading at the natural rate. They should only be concerned if they are vain enough to want to preserve the entire history that led to their appearence. To accomodate Time Patrol stories one has to assume that it is possible for time jump effects to spread faster than the natural rate. Only such temporal shock waves could threaten the founders of Time Patrol.
Still, even the shock waves do not spread instantly and the founders will have time, lateral time, to eliminate the cause of the shock wave before it reaches them. The shock wave might still erase them but the new one, the correction wave, would recreate them again. Such a theory makes Time Patrol meaningful, and placing it into a distant past makes sense assuming the shock waves only spread forward in time. From the dinosaur past Time Patrol is able to correct the alteration even after its founders were completely erased. Of course, what a clever time criminal should do is destroy their base in the past, and then make changes that would erase them from the future.
May 18th, 2009 at 8:41 pm
Thanks, Sergey, for your thoughts.
You wrote
This is very similar to the objection you expressed (via e-mail) to the Spreadsheet Illustration of Time Travel; but the answer is not exactly the same, as that replacement theory and this two-dimensional time theory are distinct in critical ways related to this point. However, perhaps I can address the concept here.
There are two ways to consider linear time. One way is that it is as it appears to us, that as we move from instant to instant the past ceases to be and the present is created, the future not existing until it, in turn, is created. The other is that it is more like a highway, the entirety of it existing in static form but we moving along it at a fixed rate. The odd part is, if the former theory is correct then time travel probably is impossible, because only the present actually exists. Time travel would have to change the entire universe, in essence by making “now” a different time, causing everything after “now” to have never existed and restoring the universe to a previous “now” from which to move forward–and leaving the presence of the time traveler as an inexpicable anomaly. Only if the latter view is true does it make any sense at all to speak of traveling in time. We can go to “then” because “then” exists as its own temporal “place”.
Under the replacement theory, when you change “then”, if it is in the past, every effect that flows from that moment must also change. In most of the discussions on the Temporal Anomalies site, time is treated as if it is progressing from one “now” to another; only in the Spreadsheet Illustration is this larger view presented, mostly for those whose understanding of time allows perceiving the entirety of time as a single highway.
You state that change cannot happen faster than the speed of light. That has one impact on the replacement theory, which I will address by e-mail; but it has a different impact here. Your problem in connection with this two-dimensional time theory is you fail to grasp that the linear time we experience is, by this theory, entirely atemporal, and the perpendicular lateral time is temporal.
What that means is that if there is a time travel event at year 1000 in linear time, it does not matter if it takes all of time for the effects of that event to reach the entire universe, because “all of time” is static, and thus instantaneous from a meta-temporal perspective. Certainly it might take a hundred years for the information related to the time traveler’s arrival to travel a hundred light years, and it might take a billion years for that information to travel a billion light years; but the time it takes for the information to travel is irrelevant, because from the lateral time perspective everything in linear time has already happened, all in the same instant of lateral time. Whether we believe time has a beginning and an end, or whether we believe it is infinite in one or both directions, the entire point of lateral time is that it is a step from one complete history of the universe to the next. Regardless of how long it takes for information to travel through the entire universe, it will have done so within the confines of the linear time that constitutes one “tick” on lateral time, because lateral time is by definition the movement from one complete history of the universe to the next.
I agree that lateral clicks could happen without time travel; I disagree, though, that there is any correlation between linear elapsed time and lateral elapsed time. The entire point is that there is no such correlation, that lateral time represents the medium against which the entire history of the universe can be changed from one complete history to the next.
This is also why your suggestion that it takes thirty “lateral” years for a change in history to propagate forward thirty “linear” years fails. A lateral tick is the replacement of the entire history of the world, all causes played to their effects.
Your belief that there are random events (which I do not share, but that is a discussion for our e-mail) gives some validity to the progression of lateral time without time travel. It suggests that those random events would be different in each progressive version of the universe. However, I find it difficult to accept. By this reasoning, it seems not merely possible but entirely likely that my birth has been erased but I do not yet know it, and the parents with whom I conversed earlier today have false memories of me being their son, but history has not yet caught up with any of us. If such random events can be changing the universe from tick to tick, then the universe has changed untold times. It is even possible (although somewhat unlikely) that my birth has been undone, that the propagation of that fact is working its way forward through time toward me, but that my birth has since been restored, and that I am alive now and alive then but do not exist for some time between.
Unless I badly misunderstand what you are proposing, that seems an inescapable conclusion of your position.
It is possible that your theory might work for the Time Patrol stories; at least, Anderson might have something like your theory in mind. It is still a very shaky notion.
Thanks again for your thoughts.
–M. J. Young
May 20th, 2009 at 12:28 pm
“There are two ways to consider linear time. One way is that it is as it appears to us, that as we move from instant to instant the past ceases to be and the present is created, the future not existing until it, in turn, is created. The other is that it is more like a highway, the entirety of it existing in static form but we moving along it at a fixed rate… Time travel would have to change the entire universe, in essence by making “now” a different time, causing everything after “now” to have never existed and restoring the universe to a previous “now” from which to move forward–and leaving the presence of the time traveler as an inexpicable anomaly. Only if the latter view is true does it make any sense at all to speak of traveling in time.”
I do not believe that there is such a strict dichotomy. One can think of driving along the highway of time with past ceasing to be and present being created, instead of moving along a static landscape. The question is if there is a single car (the Now) driving, or a neverending chain of cars (nows) in rapid succession. Our experience being restricted to a single now we do not know one way or the other. But believing that our now is the only Now is akin to placing the Earth into the center of the universe, so I opted for the pluralistic view. It still makes sense to talk about time travel with our car extending wings, flying away and landing on a different part of the highway. Since there are multiple and co-equal nows there is no need to switch from one to another or erase anything.
Perhaps you meant that in such a model time is not really time anymore, but just another dimension of space. I am inclined to agree, but any theory of time travel casts time as a dimension of space in some sense. And one does not get to create a landscape while moving along other space dimensions, so time is still special. But if you are saying that time travel is only meaningful if all new causes are instantly played to their effects then we disagree on the definition. This links directly to a philosophical position on chance and free will so I will not expand on it here.
“Your problem in connection with this two-dimensional time theory is you fail to grasp that the linear time we experience is, by this theory, entirely atemporal, and the perpendicular lateral time is temporal.”
Actually, I have no problem with the two-dimensional theory, and I agree that it has no problem with relativity unlike the replacement theory. I suggested a different theory of lateral time for the Anderson’s stories since your model does not work for them very well. Relativity is only an analogy here: we have gradual propagation of changes in space, so why not also in time since we are treating it as something like a space dimension? This does require a correlation between linear and lateral time and a new fundamental constant analogous to the speed of light, the maximum speed of temporal shock waves. Your two-dimensional theory emerges as a classical limit when the maximum speed goes to infinity. My theory sets the maximum speed equal to the natural rate of living through time.
“By this reasoning, it seems not merely possible but entirely likely that my birth has been erased but I do not yet know it, and the parents with whom I conversed earlier today have false memories of me being their son, but history has not yet caught up with any of us.”
Your description of events surrounding your birth is entirely accurate, but I would change the tonality. Your birth might have been erased and you will never know it under normal conditions (no shock waves). Your parents’ memories are not false, metaphysically and causally you are *their* rightful offspring, but the moment of *your* birth is no longer along the highway. Instead, somewhere up the road there is a couple of people, much like your parents, that do not have a son. And that history will never catch up with any of you, again under normal conditions. Causality moves not along time, which is like space, but along lateral time, exactly because it is the truly temporal dimension. Due to the correlation however, there is a simultaneous shift along the time highway.
“It is possible that your theory might work for the Time Patrol stories; at least, Anderson might have something like your theory in mind. It is still a very shaky notion.”
Is time travel ‘really’ time travel under the above circumstances? People may disagree, but my model is as descriptive and logically consistent as the replacement theory. Shock waves spoil the sport though. Why should changes made by a time traveler propagate any faster than changes made by other drivers? Let me offer an interpretation of Anderson’s story that does not require any shock waves.
Suppose the universe of the Founders in the distant future faces imminent doom at time X. It has nothing to do with time travel, could be the Big Crunch or the Big Reap that some astrophysicists are prophecising. They are working to avert it or to live through it, but they need time. Time travel technology being available to them, they go back to an earlier time, share their research with their ancestors and collaborate to find a solution. They repeated it multiple times but did not succeed yet. They can not go too far back since the people are not ready to comprehend their science, etc. If somebody in the past makes changes that prevent certain key discoveries from being made, their operational time segment will eventually start shrinking even without shock waves. Its forward end keeps rolling into time X, and its backward end is being rewritten into unusable wasteland. Since the Founders do not know when they will find a solution they need to keep this segment as intact as possible for as long (in lateral time) as possible. Hence the Time Patrol.
P.S. It has been a while since I read Time Patrol (15+ years), but I seem to recall that Anderson explicitly adopts a version of parallel worlds with return to the branch one creates. He only allows one active branch at a ‘time’ though, the rest remaining mere possibilities. There was one story with 20th century looking like brushed up 19th and the Founders erased. The character had to travel to the branch point to fix it.
May 20th, 2009 at 3:26 pm
I’m inclined to think that time travelers under your your theory face the problems I address in The Two Brothers: Why Parallel Dimension Theory Is Not Time Travel, which I know you have read. Assuming that change propagates one linear year per lateral year, a time traveler could well be caught by a very slowly advancing change in the past, travel back to the branching point, make the necessary correction, but in returning to the future wind up in the history he has already erased, because it will take that many years for the correction to propagate.
As for me, I have trouble with non-linear realities. Things are or are not. I do not think it possible that my years in college have been erased but I still remember them and my name appears in their alumni records. If those years have vanished, then everything subsequent to them must also have vanished. I’m a stickler for chain of causality, which is what drives the replacement theory more than any other single factor.
I do thank you for your input, though. Your notions do seem closer to Anderson’s stories, although I think he would insist on instant change of all history, protecting only those who have traveled from one point of time to another.
–M. J. Young
May 22nd, 2009 at 12:16 pm
Sorry M.J., I do not mean to bother you too much, but I could not help but respond. We can continue elsewhen via email.
“I’m inclined to think that time travelers under your theory face the problems I address in The Two Brothers: Why Parallel Dimension Theory Is Not Time Travel…”
I am cautiously optimistic that it does not face the egregious ones (see below). To the extent that it does, the replacement theory (and indeed, any time travel theory) has the same problems. But I understand where you are coming from. To me, the prime motive was to save room for chance and free will. I fancy my model to be the most conservative alteration of the replacement theory, provided the free will is taken seriously and played out to its logical conclusions. There is still a tint of dissatisfaction that one can not erase one’s own life and replay it better, probably the most powerful emotion behind seeking time travel. But hey, there is a price to pay for making choices: what is done is done, time travel or not. ‘Tomorrow never comes until it’s too late’.
“Until it has been demonstrated that a block of pure carbon can be reliably moved from the present to the past, no one is going to allow a human being, nor even an earthworm, to make a trip in any such machine… The ultimate problem with parallel dimension theory is that if it works it can’t be demonstrated. Thus time travel dead-ends under this theory, as no one can know whether those who vanish are in another physical world, or have merely had their atoms scattered across the cosmos.”
In short, ‘it will never get this far’ problem is obviated in any parallel dimension theory, where one can return to both the left and the created branches. In my model this is achieved by their segments sharing the same spacetime.
Suppose researchers test a time machine by sending a carbon cube one minute back. They may be discouraged by the fact that it did not pop out of nowhere one minute prior to the experiment. But they proceed anyway. The cube does pop out of nowhere in front of almost identical group of researchers that are one minute behind the original group along the highway. They proceed with their experiment and conclude that time travel works. They may notice that the returned cube is not exactly identical to the one sent, but this can be attributed to any number of effects of the trip. As long as travel times remain small their experiments will be mostly successful and will attract lavish funding.
Of course, eventually they will be shocked by receiving a tapeworm right before sending a rainworm. I trust that my hypothetical colleagues will figure out what happened. With any luck, they will confirm their hunch by having one of their own converse with their future counterparts, and come back to resolve the tapeworm paradox. It is also possible that they will first come up with a contraption that automatically returns objects back to them after a short time trip. In that case, they can perform a disappearing-reappearing act in their lab in front of senators and generals without any anomalies.
“Yet he is not your brother; or perhaps more precisely, you are not his brother… Meanwhile, back in your own world, your brother died. You did not save your brother; you saved someone else’s brother… It isn’t time travel unless the traveler arrives in his own past. That means he can impact his own life; and that means we need a theory that addresses what happens when someone impacts his own life. The theory of this site does that…”
I am afraid, *no* time travel theory can do that. Even in the replacement theory the time traveler does not impact ‘his own’ life but that of his younger self, who by that very action grows into a different person. When the traveler returns he faces this alter ego, who is the *true* kid brother’s brother. And well, he is a stranger, and he will always be a stranger. This is the outcome of the two-dimensional theory. The replacement theory is even worse: if I am not mistaken, it predicts an infinity loop here. The alter ego does not build the time machine, his kid brother being cured, and the traveler has nowhere to return, the time being trapped between 2000 and 2030.
In fact, there is no difference between the parallel words and the two-dimensional theory predictions except for a purely metaphysical question of whether the old history is preserved or erased. It may seem important that if the old history is there you only compounded the net misery, but if it is erased you took one for your brother and stayed alive. But is it really a *moral* achievement that you erased an entire world full of people to create a new ‘less miserable’ one? This sounds like something the god of gnostics would do.
For time travel to impact ‘own self’ it would have to transmute the time traveler into his younger self after he made the changes. Somehow the memories of the time travel have to be preserved but not affect this new person. Perhaps, they only resurface at the time when the jump originally occurred, etc. I am sceptical as to logical consistency of such a theory. The replacement theory, the two-dimensional theory and even the parallel worlds do the next best thing. They duplicate a person into a changer and a changee, cause and effect. This duplication destroys the possibility of changing *own* past even if you start with exactly the same past. The only difference with my theory is that I replace ‘exactly’ with ‘more or less’ simply because ‘exactly’ leaves no room to chance.
May 22nd, 2009 at 8:42 pm
Sergey, I much prefer having such conversations in open forums. That way when someone else has the same questions, they can read the answers I’ve already written instead of forcing me to write them over again. Incidently, I have been working, in bits and pieces, on my response to your treatise, in a sort of “format this to web page, and answer it on this other web page” process. I’m about half through that, and will let you know when I’m finished. I will probably also post the brushed-up version of this article to the Temporal Anomalies site at the same time.
You wrote:
That may be a matter of perspective.
If we consider my construction of Back to the Future Part I, I maintain that the original Marty McFly whom we have followed through the film ceases ever to have existed at the moment that the altered Marty McFly leaves the parking lot. If we assume that that altered Marty manages to disrupt his parents’ meeting and bring them back together sufficiently like the original Marty did, leading to his own departure from 1985, then the Marty who awakens the next day finds the affluent McFly home, but is not at all surprised by it because he has always known about it. Yet this is the same Marty, son of Fred and Lorraine, with many of the same interests. Marty really has changed his own life; he just does not know what it was before he intervened. In any case, there is no alternate Marty running around his universe; he is the only one.
The points raised in The Two Brothers: Why Parallel Dimension Theory Is Not Time Travel focus on the fact that there would now be two Martys in that world, one of whom came from the other world and the other who grew up in this one. Conveniently for parallel dimension theory, one of those Martys decided to run off and start another universe, and we do not know where he is now. However, there is this sense of displacement, that the Marty who awakens in the affluent McFly house does not really belong there, and it seems just a matter of time before he is identified as an imposter. He probably does not know his own financial position or any of his passwords (and yes, the wealthy had that technology in 1985).
Indeed, under the replacement theory the two brothers story does create an infinity loop; but it is real time travel, and not movement to another universe.
You further wrote:
I see your point, but I’m not sure it’s entirely correct.
Mind, this draft is an effort to explore whether such a theory is plausible; it is, to my mind, full of holes I cannot plug. Your efforts with supertime are fascinating, but that is not the discussion here. I am in no way committed to defending two-dimensional time; I think it inadequate for time travel. I do not, however, think that lateral movement in two-dimensional time is destroying people.
Thinking strictly in terms of linear time, I was recently declined representation by a well-known literary agent. Had he undertaken to represent me, it is possible that my next book would have made a significant impact to my immediate financial situation and my long-term future. In that sense, his choice “erased” a possible future and “replaced” it with one I find less promising. Yet I have no memories of either future at this point, and will only remember the one in which he declined to represent me.
There are those who suggest that at any given now all possible futures exist, but there is only one past; that by making our choices moment by moment we eliminate most possible futures and create a single past. Based on that perception, that agent destroyed the bright future that has me collecting royalties on books and doing speaking engagements, and created the one in which I remain a lesser-known celebrity still struggling to get on the D-list, as it were. Yet we would not say that he destroyed anything; he simply made a choice which caused changes which formed a future different from some other possible future.
If we accept lateral time, then choices made which involve time travel do exactly that, but do so across all of history. Thus if someone from the future travels back and tells that agent, “You’re making a mistake, you really need to represent this guy,” the step laterally unmakes the future in which I am not represented and replaces it with the future in which I am. That is not different from what the man (I am very tempted to use his name or agency, but I think that would be inappropriate) did initially, choosing one of the many possible futures by his initial choice. The lateral change is not different from what we now think the linear change is.
Again, thank you for your comments and insights. I hope my responses have been helpful.
–M. J. Young
May 26th, 2009 at 2:03 pm
I think Andersen had a propagation time for changes in his Time Patrol stories, but I could be wrong.
May 26th, 2009 at 5:22 pm
I think you’re right about propagation time in Anderson, but it’s rather unclear. It seems to some degree as if such changes move faster than the speed of time, and in other cases it seems otherwise. Also, in at least one story they spent the entire tale investigating an anomaly in history which they themselves create near the end of their investigation–they are trying to determine why this woman and her male friend are regarded as seers protected by the gods to the point that history is changing in response to her advice, and they trace it back to a moment when some sailors attempt to rape the young girl and one of the time travelers rather dramatically intervenes. Of course, they could not reasonably be investigating the consequences of a cause they have not yet created on pretty much any theory of time, but the point was to make a puzzling story.
That may be Anderson’s real theory: what can I write that plays mind games with temporal mechanics? I think a lot of writers in the time travel business give no thought at all to a theory of time, and instead create stories that have a feel of plausibility so they can challenge theoreticians like me to explain how they could or why they could not ever happen.
–M. J. Young