Diagonal And Vertical Time Travel

This is a bit of a thought dump where I try to work out the details of something I’m planning to use in a story, along with other bits I’ve adapted from elsewhere. It’s about time (travel).

I want to talk first of all about metaphors for the passage of time in language and, well, gestures I suppose, and it’s possible that this also comes into sign language. We tend to talk about going forwards and backwards in time, about “past” events and events “to come” and so forth. We also have links between the direction of writing, and what follows from that, and that of time. Our clocks move clockwise and progress bars on audio and video place the “early” direction on the left and “late” on the right. This has been going on for longer than the existence of easy video and audio playback on digital devices, because on tapes, for example, we have fast forward and play, with arrows pointing to the right, and rewind, with arrows pointing to the left. One thing I don’t know is whether Arabic and Hebrew use the same convention, even though their writing proceeds from right to left, but I would expect the dominance of Western culture to have dictated this. A less well-known aspect of this is somewhat more jarring for us as humans, as opposed to us as humans literate in Latin script. Languages are often described as having features to the right or the left, for example as having prefixes to the left and suffixes to the right, focussing on spoken language, but written language doesn’t always go that way, so it means that Hebrew, for example, might be described as having the definite article to the “left” of a noun even though as written that would be on the right. Incidentally, when people pause to think during a conversation, they will look to their right and up in cultures where writing is left-to-right and to their left and up where it’s right-to-left, and since this is learnt from other literate individuals and diffuses through culture that way, it’s even true of illiterate individuals such as small children. This illustrates how pervasive our time flow metaphors and conventions are. It should also be mentioned, for the sake of completeness as this probably won’t come up again here, that time can be thought of as linear or cyclical, and in theory cyclical time could be moving in any direction, although again this would depend on clockwise or anti-clockwise convention.

I could be wrong about this but I seem to remember that Chinese culture, inasmuch as it’s a single culture, agrees with my own view that the passage of time is vertical, falling from top to bottom. I presume the reason for this is the vertical direction of Chinese and related scripts, which brings me to wonder how it worked in Mongolia when it too had a vertical script. Another set of options for script direction exists in boustrophedon, where direction alternates and characters can be either inverted or mirrored, and I have no idea if that has any bearing on temporal metaphors. However, I want to put a case for a vertical time flow metaphor besides script direction, which seems fairly arbitrary, and then I can get on with this.

X, Y and Z axes are usually organised in order of left-to-right, front-to-back and low-to-high. On a graph, the Z axis usually points into the paper or screen and away from the viewer. The time axis is often referred to as W, because they ran out of letters and had to go backwards. As H.G. Wells pointed out in ‘The Time Machine’, gravity conventionally restricts our movement in the third dimension, i.e. height, in that if we consider the centre of, in our case, Earth as below us, we are liable to fall in that direction without support and have difficulty increasing our height above a reference level because it pulls us down. This difficulty is paralleled by our perception of the passage of time, because we are relentlessly propelled into later time from earlier, a process which is usually described as “forward” in time. Because of this similarity, it makes more sense to me to think of the passage of time like a waterfall, falling from top to bottom, and also as facing upwards since we have greater difficulty with accurately perceiving the future than the immediate past. This also has the advantage of working better in gestures and diagrams, because a vertical picture of the passage of time is the same for all observers, unlike time itself, whereas a time flow metaphor of forwards and backwards, or left and right, is reversed for someone opposite. That said, I’m pretty sure I don’t consistently gesture in this way. This vertical metaphor also works for the likes of family trees, and may also be used for timelines although this contradicts the order in which, for example, strata are laid down. A chronicle written in Latin script would, however, proceed vertically down the page, in a scroll, and in a codex (spined book) this would also be true when it was closed – the Book of Genesis is at the “top” of the Bible and Exodus is underneath it, in an English Bible, though in the Tanakh it’s the other way round. Family trees, incidentally, are actually the other way up compared to real trees.

Thinking of spacetime as a block, and simplifying space to two dimensions to make it possible to visualise it, it can be thought of as a kind of transparent cube with events embedded in it like flies in amber. The longer something goes on for, the longer its world-line is, from top to bottom, and at ordinary speeds, something moves around horizontally but is always earlier at the top than at the bottom. Then there’s the light-cone, which I regard as a crucial concept for time travel. The Sun is eight light minutes, Alpha Centauri four light years and Betelgeuse six hundred light years away. The upside-down, but still vertical, version of the light cone can be illustrated thus:

Flipping this over, events occurring above, such as the emission of light from a star, have only impinged upon an observer at the peaks of the cones if it happens within the top cone, and events occurring below, i.e. in the future, will only influence other things if they are within the light cone below the point where the peaks meet. The surface of the cone is defined by the speed of light because nothing can exceed it, and therefore there can be no causal connection between anything outside the light cone. Every location at a particular moment has these light cones.

This is where time travel comes in. The classical objection to travelling backwards in time is that it can create two types of paradoxes, or rather involves two types: the grandmother paradox and the ontological paradox. The grandmother paradox is illustrated most starkly by the possibility of becoming one’s own grandparent, leading to a loop in time with no cause and also a contradiction with recorded or otherwise “known” events. I know I’m not my own grandparent, or have a high degree of confidence that I’m not, because their identity and history aren’t mine. A slightly different paradox is the ontological one, exemplified by such events in fiction as the apparent eighteenth century CE glasses given to Captain Kirk by Bones in ‘Star Trek’ which were later pawned in 1986 in San Francisco, later possibly being acquired by McCoy and regifted. This means that certain complex objects have no origin at all, and raises questions such as what happens if someone sends a 21st century signed copy of the sheet music for Beethoven’s Fifth Symphony to Beethoven which he then copies instead of composing it for himself. It might be less disturbing if all that happens is a single electron or photon is transported in time.

My long-standing answer to this is to evoke what is called either the Novikov Self-Consistency Principle or the Blinovitch Limitation Effect, depending on whether you go with the real world or science fiction version of the effect. The Novikov Self-Consistency Principle holds that if an object travelling in time would cause a paradox of this nature, the probability of that occurring is zero. The Blinovitch Limitation Effect is similar and originated in ‘Doctor Who’, and means that either timelines cannot cross themselves or that if they do, some kind of catastrophe occurs. This happens for example in ‘Father’s Day’, where Rose encounters herself as a baby and it leads to damage to the time stream which can only be resolved by her father meeting his fate, that is, death under the wheels of a car.

My own solution to this has been to suppose that time travel “upwards” is only possible outside the light cone. That is, for example, you can move upwards in time but if you did so you would find yourself displaced at least the same distance in space from your point of origin as it would take light to travel to it by the moment of your departure. Hence if you travel three years upwards in time, say from 2023 to 2020 you might find yourself near Alpha Centauri because it then means that you can’t have any influence on where you came from. You might send a radio message warning people about Covid-19 but it wouldn’t get there until after the outbreak, for instance.

For this reason, I have tended to portray time travel as a “diagonal” process. You can’t stay in the same place and travel into the past, but will be displaced by the same distance in time and space: four light years for four years and so on. I also applied this to the idea of parallel universes, which I see as separated from us by extra dimensions, so your creation of a different history would simply mean that you had been transported to a parallel universe where that would always have been the case. The problem with this is that it kind of makes it look like any significant historical event was caused by time travel, or that there would be duplicate universes different only because in one a time traveller had turned up and made the same change as had happened without such intervention in another parallel universe. Thus in one universe, JFK isn’t shot because the guns jammed but in another someone came along and secretly did something to the guns in advance which caused them to jam. This seems suspicious.

There is a further problem with intersecting light cones, because events which can’t impinge on one light cone can do so on another, but I have to admit to being rather hazy about that, so I won’t go further. That, then, is diagonal time travel. There’s also vertical time travel.

Vertical time travel is what any object or person does when they’re sitting still, although of course real sitting still (or standing still) is not a trivial, or maybe not even a possible, thing because of things like orbits, rotation of planets and so forth, and the probable complete absence of an absolute frame of reference. Hence a vertical path through time is not a straight line, although it might look straight to observers who are stationary with respect to the object or event in question. Simplifying this, as in fact we always have to deal with this in other ways but generally think of ourselves as moving or stationary with respect to the scenery or neighbourhood as opposed to the reality that we are on a rotating, orbiting planet and in a solar system orbiting through the Galaxy, and so forth, time travel from the past to the future for most of us is almost perfectly vertical in nature. We are moving straight “down” in time, not diagonally. Sunlight is diagonal. In fact, all light in vacuo is diagonal because its velocity is the same for all observers.

Back to vertical time travel. Ignoring the complications mentioned just now, vertical time travel into the past should be impossible. Into the future it’s the norm. However, the conventional depiction of time travel in most popular culture is that of the protagonist moving through time, either into the future or the past. The latter clearly brings up the question of paradoxes, and conjures up the idea of a wise and intervening Universe for which there is no evidence stopping such things from happening. This is not, though, the only conceivable way an object or entity might move through time, and this is where my new ideas come in, and where this becomes a kind of world-building thought dump.

There is a second, less often used, version of time travel in fiction which is not used to explore paradoxes so far as I know, and it’s this which I’m going to call “vertical time travel”. This is illustrated only occasionally, as far as I know. The first example which comes to mind is found in Isaac Asimov’s ‘The Ugly Little Boy’. In this story (SPOILERS!) a Neanderthal child is brought into the twentieth century, although he eventually returns to his time with his H. sap. nurse. In this story, energy is required to hold objects in the modern world and budgetary constraints lead to them being returned to the past, including ultimately the Neanderthal boy, so this is not a one-way street and paradoxes are still possible. The TV series ‘Primeval’, which I haven’t seen, seems to have the premise of a similar effect where animals arrive in the present through temporal anomalies, but again this seems bidirectional. You also see the same kind of thing in «Les Visiteurs» and ‘Catweazle’, where a similar process brings characters from the Middle Ages into the twentieth century. Most of the time, perhaps to provide resolution in plot terms, the protagonists or objects are returned to the past and I can’t offhand think of any unidirectional time travel stories. They probably do exist as they allow for “fish out of water” stories. In fact most of the time this is satisfied by the idea of someone going into a state of suspended animation and being revived, as with ‘Rip van Winkel’, ‘Idiocracy’, the story that was based on, and Woody Allen’s ‘Sleeper’. This is a device allowing for time travel in a much more realistic manner than something like ‘Doctor Who’. However, actual vertical time travel allows for other possibilities which are quite intriguing and not available to such tales.

Time travel into the past can never be invented, only discovered. Look at it this way: the first time in history someone devises a time machine that goes upward in time, it will already have gone into the past. Hence it will have come into existence before it was invented. It might not be discovered in the sense that someone comes across it on its trip furthest back into the past, but the “inventor” has come across the machine at a later time than when it first sprang into existence. Alternatively, time travel might exist due to a peculiar combination of events and circumstances arising without the intentional use of technology, perhaps, for example, where a wormhole has orbited another at relativistic speeds due to one side being close to the event horizon of a black hole, resulting in an object able to capture masses and transport them to an earlier time in its history because time has passed more slowly at one end than the other. Incidentally, I’m not saying this is feasible, but such a situation could be discovered and wouldn’t’ve been invented. Hence there is a sense in which it’s impossible to invent a time machine completely aside from any technical reason why they would be impossible in themselves. Even possible time machines cannot be invented.

Given that, there is also a sense in which instances of time travel from the past might be discovered rather than deliberately or accidentally perpetrated, but I’ll come back to this. For now, imagine the following scenario. Objects move from the past to the present without ageing. By “ageing”, I mean any change due to the passage of time, so for example if a watch reading 4:45 pm moves an hour down the line, it still reads 4:45 pm on arrival, at 5:45 pm, and it still works. This amounts, I suppose, to the suspension of entropy, although it would seem inevitable that the object in question would not have a location, and in a sense would not exist, between the two occasions. It isn’t frozen in time: it has discontinuous existence. Otherwise any object on the surface of this planet, assuming it follows Earth, would remain in the location it succumbed to time travel and would seem to be a frozen item whose location could be discovered, and it would be observed. But maybe it wouldn’t, because this would involve interaction with the rest of the universe, and this would seem to imply change. Being subjected to millions of years of ionising radiation in an instant, and millions of years of thermal energy in the same time, would be likely to destroy such an object. Therefore suspension of entropy would mean the apparent absence of the object, perhaps existing in a merely latent state for geological epochs. After all, if time isn’t passing for an object, its electrical charges cannot attract or repel, its particles can’t change energy state, preventing their ability to emit or absorb photons, it has no weak interaction in its nuclei and so forth. It literally does nothing and does not interact with the Universe, although it has to be assumed that it retains momentum or it would end up buried inside the planet or in deep space.

This, then, is the fictional scenario I wish to present. There are objects which enter a kind of dormant state of existence for various intervals, or perhaps they simply enter a dormant state of existence until disturbed in some way. Then, after a period of time, a device comes along which can revive them back into existence. This does not occur causally, i.e. this is not a device which can actively retrieve objects from the past, although that is what it appears to do, because sub specie aeternitatis this is what would always have happened to such objects. Because of this, there can have been no interaction between such objects and the operator of the “discoverer” machine, or a paradox could be created. Even so, the operator of the discoverer subjectively experiences the decision to focus the machine on a selected target in the past which they would then bring into the present. That decision, though, was always casually determined, perhaps like all apparent instances of free will. Therefore, as far as the operator is concerned, they are making a decision to retrieve an object from the past, operating the machine and being presented with the intended object. So far, so good.

From this description, there seems to be no possibility of paradox, which makes it rather boring. Consider this though. If you have already interacted with an object in some way, you cannot bring it into the present. You can’t target last night’s dinner just after you’ve cooked it and eat it tonight, because if you did that you wouldn’t have had last night’s dinner. That said, what if you targeted someone else’s dinner from last night? You’ve had no causal interaction with that dinner. It could be in a kitchen you’ve never visited and be eaten by a complete stranger. What if that led to them developing a false memory that they had eaten the meal, because in one timeline they had but in yours they hadn’t?

To be highly specific, just suppose you went back to the set of ‘Moonraker’ and removed Branche Ravalec’s braces. You would then know what had happened, but everyone else would have the false memory of her having braces when they watched the film. In other words, and I would stress that this is fictional, this is an explanation for the Mandela Effect.

And it has legs! Now imagine a sealed box containing a cat. You have no knowledge whether this cat is dead or alive owing to a poison gas canister broken or remaining intact according to radioactive decay values. Also, you save the cat by removing her from her predicament before the canister is at all likely to be broken. A familiar example, but with a twist involving time travel. If you’d opened the box, you would never have succeeded in bringing the cat through time. Schroedingers Cat of course, but with a twist.

Now imagine a young woman shopping for groceries – yes, this is a heteronormative example. Her bag falls apart and her orange rolls along the pavement, to be picked up by a handsome young man. Their eyes meet and the rest is history. There are wedding bells and children. Then, one day a third party focusses their discoverer on the aforesaid orange and removes it to their present day. For that individual, this was always going to happen because they don’t know these people and it has no consequences for them. Meanwhile, spouses wake up in their own beds, perhaps at opposite ends of the country married to different people, with different children, with no memory of how this happened or anything, but with distinct memories of meeting each other, getting married, settling down and having children, who will now never exist. On the other hand, assuming they can do anything about this, and I suspect they can’t unless they can trace who did it and stop them without causally interacting with them, and how could that happen, they would end up back together but again, their own children conceived with their other partners would, again, never have existed.

I would maintain that all these possibilities are highly fruitful, and intend to write a story based on them. In the meantime, this post has served as a means of working out this detail of such a story for me. Thanks for your patience.