Date:  Fri, 16 Oct 1998 15:23:40 +0000
From:  Holger Thiemann

Hello,

I'm sorry for the late answer, but I had no time the last week. OK. let us advance to the next round :-) By the way. Of course you may publish or discussion on your pages. I think they could perhaps inspire other people to link in.

First I agree with you about the free will. I Misunderstood your Point of view last time. The Problem about the difference of two identical things is a physical or metaphysical. If you are not able do distinguish two twins, they are of course not the same, because you can at least distinguish them, if you see them both. They are not the same, because they differ in their location. But if they wouldn't differ in their Position, let us say they melt together and will perform the same actions in the future so they will never unmelt again, then I think it's a pure metaphysical question if they are one or two, because practical they are the same. And once again, in quantum physics there are laws, that two particels in nearly the same location must not have the same state. And the uncertainty relation of Heisenberg says that it is not possible to get both the position and impulse of a particle with great accuracy. This both does not mean that we aren't able to distinguish the particles any more, but it means that the universe itself is not able to distinguish them. The uncertainty relation is the cause why electrons can't exist in the core of an atom. Their mass is to small so that their position can't be known as exact as the position of protons and neutrons. Because the core of an atom is so small, they simply can't be there, because even the universe is not able to give such a light particle an position as exact as an atom core. So you see sometimes the argument that we can't do anything could mean that it is impossible at all even for the universe and so it could be possible that even the universe could no longer distinguish between the two universes. I agree to you with your explanation of the moral consequences. I didn't mean that all combinations of particles should exist in parallel. Of course just the "possible" universes could exist in parallel, which are linked with a chain of causality back to the big bang.

Unfortunately I must agree to your statement about humanity. I don't know which time theory is right. Therefore I hope that Time Travel will never be discovered, because humanity would surely manage to extinct itself if your theory is right.

But I think the problem with the multiple version of a time traveller is not solved satisfactorily. Let us say we are approaching point D. Someon has to travel back in time before point D because otherwise time would snap back to an infinity loop. The chances that someone travels back exactly at Point D are zero, even if time perhaps is quantized. So there a two possibilities.

1. Nobody travles back before Point D (but perhaps would a few seconds later), so future is destroyed by an infinity loop.

2. Somebody travels back before Point D (perhaps a few seconds or fractions of a second), so that the resulting Point D lies before Point B. Of course any further Point F,H,J has to lie beforer it's predecessor, to avoid an infinity loop. So the peaks of your sawtooth snap would not form an horizontal line, but a falling line.

The arrival has the same problem of zero chance to lie exactly at Point A (or C or E). So you have two possibilities for the arrival, too.

1. You arrive a little bit earlier (before the last arrival). Then the lower peaks of the sawtooth would form a falling line, too and we have no problems with duplicate time travellers, because the previous arrival is overwritten. The problem is, that the sawtooth will grow deeper and deeper in the past and eventually nobody will be able to travel back so early. Thus an infinity loop will occur.

2. You arrive a little later than the last time. Then I think there has to be an other you. Think about travelling back 10 years and then after 5 years travel back again 3 years. Would you meet your other version who has arrived 2 years earlier? Or is the original timeline restored till the point of your second arrival, because the first departure is overwritten (or is it not because point D lies before Point B and the departure at B does still exist?) If it is restored, then if I travel back near Point D and I travel back just a few seconds than I should create a short E-F Segment where the history from A-B is restored from A-E? I don't think, that you mean this. So do I meet my other self or not?

To clarify the second possibility. I Travel back at B let us say ten years. Then I influence my younger self to travel back not 10 years later at Point D but just 5 years later. And I influence him to travel back just 1 year. Then he should meet me again 4 years after my arrival and this would not astonish him, because from his Memory he knows that I was there in his History. Is that all right?

So there are 3 Possibilities for every sawtooth.

1. Nobody travels back before the autommatic snap back and we have a Infinity Loop.

2. Someone travel back before the automatic snap back and arrives earlier than the last lower peak of the sawtooth.

3. Someone travel back before the automatic snap back and arrives later than the last lower peak of the sawtooth.

If you endlessly repeat 2, then your sawtooth would move more and more to the past, eventually before the invention of the time Machine, so the next time you have case 1. If you repeat endlessly 3, then the segments become shorter and shorter until you will have only the possibilities 1. or 2.

So I see no possibility for traveling back in time without causing an infinity loop in the end. Therefore if, according to Stephen Hawking it is a daily event, that energy quants and perhaps even particles travel back in time through black holes, than time should be caught in infinity loops back till shortly after the big bang.

What do you think about it?

Best regards,

Holger

Holger--

No problem about the delay--I can always use a breather to get to some of my other web sites.  Let's see where we are in the new round.

"If you are not able do distinguish two twins, they are of course not the same, because you can at least distinguish them, if you see them both. They are not the same, because they differ in their location."

Perhaps here is our complication.  If we are to assume that universes diverge from each other, it seems to me that intrinsic in that is that they must develop a different location.  In one of the letters I've recently posted, I explain why time is a concrete dimension by showing that two objects cannot exist in the same dimensional location, but doing so at different times enables them to do so in three spatial dimensions.  If two universes are to diverge and continue in the same three spatial and one temporal dimension, there must be some sense in which they are not in the same spacetime.  Although it is plausible to suggest that they occupy distinct points in a fourth spatial dimension, it is more commonly held that they occupy different points in a second temporal dimension--thus the concept of "sideways time".  Our two universes must occupy different locations in a dimension which we cannot perceive--else they would interfere with each other.  Once one universe has moved sideways in this way, even were it to move back such that all of the events within it in "the present" matched the universe from which it diverged, it would, like my twins, still be in a different "place" dimensionally, and so could be distinguished by this.

Particle physics is not my field--far from it.  However, the Heisenberg Uncertainty Principle states that it is not possible to measure the position of a particle and its energy level at the same time.  If I understand it correctly, it would be somewhat analogous to trying to understand the movement of an object in a still photograph.  The photograph enables you to see with great accuracy where the object is at that exact moment, but tells you nothing of its velocity or direction.  Heisenberg doesn't mean that a particle doesn't have both a position and an energy level at any given instant; it only means that its energy level and its position cannot be detected simultaneously.  Also, it has nothing to do with why electrons are not found in atomic nuclei.  Quite a few particles smaller than electrons, including muons and tachyons, are found within the nuclei of atoms, and are also ruled by that principle, if I understand it aright.  (This doesn't prove you wrong--it merely means that you can't prove it by that argument.)

You agree with my observations on moral choices, and suggest that "just the 'possible' universes could exist in parallel".  I would push the argument further.  I think that there is only one "possible" universe, the one which actually exists.  My argument has been that there cannot be so many universes in which I and everyone else have inexplicably chosen evil, chaotic, and destructive actions, in large part because we each make our moral and ethical choices based on aspects of our characters and personal belief systems so ingrained that someone who knew us well enough would know what choice we would make.  But I suggest that this is true of every choice we make, right down to which words I will use in this sentence to express the thought which has been inspired by the letter you wrote me, which was inspired by the letter I wrote you.  As free as we are to choose whatever we wish, we will always have chosen what we chose were we able to live it over again for the first time, that is, without any knowledge that it was repeated and without any change in the events leading to it.  I think the notion of an unpredictable event is merely a limitation on our ability to collect and process information rapidly and completely enough.  I am one who believes that God knows the end from the beginning--but much like a chess grand master, could that not be because He is able to comprehend the entire chain of effects from the original cause, and know precisely how each of us will respond to any move He makes?  Once you admit that our choices are deeply rooted in our histories and personalities such that they would be predictable given total information, you have established that there are no alternate worlds based on different choices.

Yes but, you might say, the other me could have experienced something different in his past which causes him to choose differently in the present--but you only push the problem back a generation, because there is no reason for anything to have been different to cause that change of experience; and you push it back generation by generation, century by century, eon by eon, until you have determined that there were two different big bangs--and at that point, you're not talking about a universe which diverges from this one, but one which was always distinct.

I, too, hope that time travel will never be discovered, and for the same reason.  I've written a short story along those lines, and am seeking a publisher to carry it--perhaps an e-zine, although I would by pleased to have it appear in more traditional media.

You think the problem with the multiple version of a time traveler is not solved satisfactorily.  You suggest that "the chances that someone travels back exactly at Point D are zero, even if time perhaps is quantized."  I'm afraid I'm going to have to object to that.  But first, you've brought up a significant point--are there minimum units of time?  It appears that there might be minimum units of space somewhere below the subatomic level.  If time exists in "chronotons" or some such particle, it might be that there is some infinitesimal fraction of a second which is the smallest difference in time possible, and that two events which happened during the same chronoton would be simultaneous in some ultimate sense.

It also raises the opposite question--is there some level of allowable variance in the time travel event?  Time travel in dramatized science fiction is never instantaneous:  the time machine always requires a moment to achieve its result.  If we suppose that the time travel process involves the operation of a machine which builds up a temporal displacement field or charge over the course of three minutes, and then releases that in the transfer of matter across time--and were we to further suppose that once this is begun, it cannot be stopped or reversed--then it might be possible to suggest that a time machine started in the CD segment two minutes later than it was started in the AB segment would maintain the chain of causality--it would at that point be inevitable that someone would go back in time, even though the temporal event itself would not happen until two minutes after point D was reached.  These are questions about the physical nature of time and the technology which would be able to breach it, and well beyond our meager abilities to predict.

But my objection is that I believe it quite possible that a time traveler would leave point D exactly and return to point C (or E) exactly.  It has to do with the nature of the CD timeline.

Let us assume for the moment that the time machine is part of a space mission.  We are going to send a probe to a distant galaxy; the probe contains powerful transmitters, information gathering equipment, and a time machine.  We will launch the probe in our time, and let it travel at near light speed into a distant galaxy--arriving not less than hundreds of thousands of years in the future.  As it arrives, the energy of that galaxy activates the dormant time machine, throwing the probe into the past hundreds of thousands of years.  It then gathers tremendous amounts of information, and transmits it back in our direction--a transmission which will take hundreds of thousands of years to reach us.  We are waiting for the transmission, which arrives shortly after we launched the probe, giving us a tremendous amount of information about the other galaxy in the distant past.

In fact, that probe's presence in the other galaxy long before man existed on earth is a change in history--time in the universe must be repeated to accomodate this alteration.  But I think that you would agree that the effect of that change on any aspect of the launch of that probe would be negligible--you might even accept the contention that such effect would be zero.  I maintain that any events which are not influenced by the time traveler will be unchanged.  Thus, to cite myself from elsewhere on this site, if in the AB segment I decide to make a random choice by flipping a coin, and I reach into my pocket, draw out a coin, flip it, and follow the results of that random action; then in the CD segment, if the time traveler has not affected me in any way, I will make the same decision to flip a coin at the same instant, pull the same coin from the same pocket, assign the same values to the two sides, toss it with the same force on the same point at the same angle, catch (or miss) it at the same instant, and get the same result.  Even the wind which shifts the coin will be identical in the CD timeline, because for everything except the time traveler, this is the first time, and it is precisely the same as the first time, except in those ways in which it is altered by the ripples of the presence and actions of the time traveler.

Thus if the time traveler does not do anything which would in any way affect his younger self, the time machine, or those involved in creating and operating the time machine, then at point D, the same traveler should make the same trip from the same instant to the same instant.

I admit before you object that a time traveler could go out of his way not to affect the time travel in advance and still influence it; but I think it possible for the time traveler to perform his actions precisely at the end of each time line if his history has not been altered in a way which would cause him to act differently.  (I will note that this becomes a problem for Back to the Future 1, as the Marty McFly whom we see going back in time at the end of the CD segment is acknowledged by us to be a changed Marty McFly with a different upbringing; yet it is still within the realm of possibility that those changes to Marty would not change the way he reacts to the Libyan attack at all.)

But your scenarios are still interesting.

If nobody travels back before Point D (but perhaps would a few seconds later), the future is destroyed by an infinity loop;  apart from the musings a moment ago regarding the possibility that the inevitable preservation of causality might stretch the deadline, this is correct.

If somebody travels back before Point D (perhaps a few seconds or fractions of a second), I would treat these trips as distinct temporal events.  That is, if in the CD segment anyone including either temporal version of the original traveler goes back to any point in the past from any moment before point D--whether it be a year or a picosecond (overlooking for the moment our doubts regarding the necessary level of exactitude in the timing of the event)--is making a different trip, beginning a new anomaly; once that anomaly is resolved, point D could be reached in the original anomaly, and would still have to be resolved by a trip back in time.

And again, if there are no changes in the CD timeline that would affect anything related to the time trip itself, the unchanged traveler of the changed timeline should land at exactly the same instant in the past as his original version, unaware that he is not the original.

Still, you could have a series of nested time trips or overlapping time trips reaching farther into the past, and in some cases these would overwrite previous subsequent histories.  However, it would require a very careful consideration of a much more detailed scenario before I could determine whether you would find your future self in that past--the recently added Lost In Space page contains similar convoluted overlapping temporal anomalies, but it's not a good example.  Back to the Future 3 includes a look at the interlocking timelines of all three films, which loop and snap and jump in many contorted ways.  But since it is not intrinsically necessary that the traveler in the later segment would not be able to reach the identical point in the past, we are not ultimately forced to an infinity loop.

If you travel back 10 years and then after 5 years travel back again 3 years, do you meet your other version who has arrived 2 years earlier?  You do.  Imagine it this way.  Traveler 1 leaves point B and arrives at point C.  Before point D, Traveler 2, unaware of Traveler 1, leaves on his own trip--a different time trip initiated within the CD segment.  He leaves from point B2; when he reaches the past, he creates point C2.  If point C2 is after point C, then Traveler 1 is already there, and he becomes caught in the altered history of this new anomaly.  Time will progress until it reaches point D2; at that point, if Traveler 3--the one in segment C2D2 who has never made a time trip--repeats the trip made by Traveler 2, we may have an N-jump, and history will continue past D2 to reach D.  At that point, the larger anomaly must be resolved, in this case by the very unlikely event that Traveler 3 will now duplicate Traveler 1's trip.  Note however that if Traveler 3 does not repeat Traveler 2's actions, our infinity loop is caused, forever alternating between A2B2 and C2D2; but both of these are variants of segment CD, wholly contained within it, so Traveler 1 is present in both of them.

However, for this to happen, Traveler 1 would have to have changed history in some way which caused Traveler 2 to make a trip earlier than the one made by Traveler 1, and to target a different moment in the past.  If Traveler 1 has not impacted on Traveler 2 in any way, Traveler 2 will leave D at the exact same instant Traveler 1 left B, and arrive in the past at point C to repeat the actions of Traveler 1--in a sense, the two merge, as history has stabilized if the identical person makes the identical trip.

If you travel back from B ten years, then I influence your younger self to travel back just 5 years later only 1 year into the past, you will meet yourself there, just as you remembered you being there.  But this is a different trip taken at a different time for a different reason, and creates a new temporal anomaly within the old one.  But you've probably created the infinity loop on the anomaly you caused when you came back ten years, since your younger self is unlikely to be the same person making the same trip if your point D is ever reached.

So there are not just three possibilities, but several things which can happen at the future end of any anomaly.

1) If nobody travels back before the automatic snap back, we have an Infinity Loop.

2) If someone travels back before the automatic snap back and arrives earlier than the last lower peak, this is not the sawtooth snap--this is a second anomaly created within the CD segment of the first and extending before the first anomaly.  It creates very complex time lines.

3) If someone travels back before the automatic snap back and arrives later than the last lower peak of the sawtooth, this again is not the sawtooth snap, but a second anomaly this time contained within the CD segment of the first.

4) If traveler makes the same trip from the same time to the same time, but has been altered in some way which causes him to act differently in this segment, he creates the EF segment and the Sawtooth Snap.

5) If traveler is unchanged, he makes the same trip from the same time to the same time and performs the same actions in the same way such that the history of the CD segment is repeated precisely.  If any segment of the anomaly is repeated precisely, it is established as history--that is, it causes itself, and therefore perpetuates itself; in this case, time continues through the N-jump.

Stephen Hawking's reputation preceeds him; if he says that time travel is a daily event, that energy quants and perhaps even particles travel back in time through black holes, I think it very likely that he is correct.  But with particles and bursts of energy it is even more likely that the events will repeat themselves precisely, because they aren't going to think about it.  If they do indeed exist (and I note first that Hawking would be my first choice for an authority on the question, and second that Omni magazine once published an article stating that some other scientist had demonstrated that if as much comes out of a black hole as Hawking claims, the black hole would dissipate rapidly upon formation, and thus could not exist for more than an instant), a natural jump backwards in time would be driven by physical forces in much the same way as a water droplet on the eaves over your window.  Although you and I might not be able to predict the fall of that droplet with any precision, in fact the droplet is gradually gaining in size and weight as it fills with run-off from the roof above, and at the instant that it is too heavy to hold itself to the eave, it will fall.  So if we imagine a tachyon suddenly jumping backwards in time to another atom, it now is a temporal duplicate of itself, but that same original tachyon is pressed by the same forces which caused it to jump in the AB segment so that it, too, will make the jump in the CD segment made by its temporal duplicate in the AB segment, and the duplicate will continue into the future beyond D.  If it happens as often as you say Hawking says, then the universe is constantly hiccoughing as it progresses--but since none of us are aware of it, it doesn't much matter.

The alternatives to my theory are 1) that each of these seemingly insignificant skips backward in time is creating a new universe with a different history (parallel universe theory), or 2) that causality is illusory, and all events happen in sequence as scheduled, including our prescheduled actions which we incorrectly perceive as choices we make (unalterable timeline theory), or 3) that there's another way to understand timelines which is better than mine, but which we have not discovered.

And as proof of my assertion that people's actions are predictable, I'm willing to predict that you'll have another excellent question for me fairly soon.  In fact, I'm looking forward to it.