Taxonomy of teleportation models

Teleportation is when a physical object travels from one place to another without passing through the intervening space.

Teleportation is, at least to a first-order approximation, fictitious. However, when it does appear in fiction, it frequently has some kind of logical underpinning, and it becomes interesting to break down those various models. In fact we come up with a sort of taxonomical tree.

Wormholery

The subject travels through some sort of "exotic matter tunnel", "Einstein-Podolsky-Rosen bridge", "folded space" etc. etc., reaching a distant location through what essentially amounts to a shortcut. Examples: Stargate, Portal.

This is not teleportation. Although it is true that the subject did not travel through most of "the intervening space", there are numerous physical routes between locations in the real universe; a wormhole in the usual sense is nothing more than regular space, highly distorted or contorted or warped or compressed to present one route which is much shorter than all of the others. This is basically just walking.

"Printing"

The subject is physically scanned and dismantled; a signal representing the scanned information is transmitted to the destination, where nanobots assemble a copy from raw matter already present there. Example: Glasshouse. (I think?)

This, also, is not teleportation. The signal (the "transporter buffer", if you will) is not matter; the matter at the source stays where it is and the matter at the target was already there.

Note that this is already completely possible to a relatively low degree of fidelity, all you need to do is hook up a 3D scanner to the internet to a 3D printer. And, oh, make sure you break the original apart with a hammer once you're done.

Accidental duplication is absolutely a potential problem here. Preventing deliberate duplication is also a problem, as there's no serious reason why the transmitted signal can't be stored indefinitely and reused.

If used successfully on a human, this is simultaneously murder and something significantly more legally and ethically complicated; the production of a new living human from thin air, one who is unquestionably not the original. (Plus, the whole "souls" deal.)

*

Alright, with those "fools' teleporters" discarded, we can break the remaining models down using a simple question: What happens at the destination?

"Nothing at all": Fraudulent Teleportation

What appears to be, and is popularly sold as, a "teleportation unit" is in fact merely a disintegrator. The receiver/reassembler technology does not exist, or exists but is not in use; smoke, mirrors and cajolery are used to conceal this fact from the victims. "Oh, the destination colony is four and a half light-years from here! You won't get a response for nine years... Unless you feel like following them?" The operator collects the victims' assets. Source.

This, again, is not teleportation.

Crowbar Teleportation

When the teleporter fires, a gap is somehow forced open at the destination and the source volume of matter is inserted. This probably leaves a vacuum at the source, which implodes noisily unless something prevents this. In this model, the crowbar effect is a direct result of using the teleporter — maybe the arriving "packet" of data forces everything out of the way as it descends/unfolds from some higher dimension. (As opposed to some secondary machine opening the gap deliberately to make room. More about that in a second.) Example: can't provide one off-hand; I used something similar in Ra, but that's really nanobot "printing".

Forcing air molecules or even grass or dirt out of the way at the destination probably isn't too much trouble, whereas teleporting into a volume of solid steel is cause for more concern; how much force does this take? How much force does the incoming matter exert to create this space? What happens if it isn't physically possible to force a large enough gap open? Does the source volume get compressed into a smaller space? Does it bounce back to the source somehow?

This has the interesting side-effect of turning teleportation into an effective way to selectively distort the internal structure of physical objects.

Telefragging

All the matter at the destination is annihilated to make room for the incoming matter from the source. Again, a vacuum is left at the source; again, the annihilation effect is considered to be a direct result of applying teleportation technology. There is NOT some secondary device which "clobbers" the target volume to prepare room for what is incoming. Example: Team Fortress 2 (sort of).

This, like the crowbar model, has an interesting side-effect: completely aside from the teleporter, you have just created a working, potentially arbitrarily far-ranged disintegrator. Just teleport fresh air over the top of whatever it is you want gone!

Real, live, working teleportation is, in all its forms, a colossal game-changer. Like time travel, it undermines and destroys fictional universes.

This model possibly violates the law of conservation of mass/energy, unless the matter at the destination is e.g. converted into energy (boom) or perhaps displaced into some other dimension. Or maybe, like the second domino, it is catapulted off to some third destination, where it displaces still more matter off to a fourth destination, and so on?

Splice Teleportation

Nothing happens to the matter at the destination; all of the particles of the source volume are interleaved with the particles at the destination. Example: that one issue of Top Ten (basically). Maybe The Fly?

This is almost certainly fatal for all living creatures, because there shouldn't be air inside all of your cells and organs, let alone solid matter.

The standard method to prevent this is for some kind of secondary machine (remember?) to deliberately open a hard vacuum at the destination prior to the arrival of the source matter.

Without these precautions, a person can end up phased through a wall or a floor or another human. Even if being riddled with unwanted oxygen and nitrogen molecules doesn't kill you — which maybe it won't, I'm no biologist, corrections will be along soon I'm certain — this is very bad news. You're going to lose that part of your body.

Some interpretations of this model hold that the inevitable result is a nuclear explosion, because the source atoms and target atoms end up close enough together for atomic fusion to occur. This... doesn't seem too likely to me? Atomic nuclei make up only a tiny fraction of a whole atom. And even if a few nuclei ended up genuinely interpolated into one another, creating a heavier nucleus and releasing some energy, why would that cause a chain reaction?

Free Exchange Teleportation

The matter at the target destination is sent back to the source. Effectively, using the teleporter near-instantaneously exchanges two (presumably identical) volumes of space.

This is the interesting one.

This model is elegant and effective, simple, non-fatal, plausible... and incidentally implies causality violations. At least one, possibly both of the volumes involved in this "instantaneous" exchange have travelled backwards in time from certain perspectives.

This model can perfectly adequately support quite a lot of really good stories in the same way that Newtonian mechanics can support quite a lot of really good physics, and it's only once you start actively pushing the extreme limits that the causality problem rears its head.

Note that if the target volume doesn't return to its destination instantaneously, then we have to revert to one of the prior models when that target volume does arrive. Something else has to happen: it has to obliterate the destination, interleave with it, or force it aside.

Simple variant: Three Exchange Teleportation: source arrives at target, target volume "disappears", matter from a MYSTERIOUS THIRD PLACE arrives at source.

*

Good! What other ways are there to classify teleportation models?

Orientation conservation

It would be easy to conceive of models where the orientation of the teleported volume at the source and target have to match, so that when beaming down from a spaceship to a planet, you usually arrive upside-down or at some stupid angle. Conservation of spin, maybe?

What's less easy is conceiving of a useful in-story reason for this to be the case, which is why you generally don't see it.

Velocity conservation

Slightly more interesting is the question of retained velocity. Without something to match the relative velocities of the source surroundings and target surroundings, teleporting down from a spaceship invariably leaves you hurled into the nearest wall at several kilometres per second. To my knowledge, this never happens in Star Trek, even in that one episode where they were transporting in-flight bullets around. It gets employed to pretty great effect in the Discworld book Interesting Times, though.

Of course, if this isn't a fundamental feature of the science of teleportation, then presumably some secondary machine is helping you out here. Which is to say, modifying the velocity of a group of particles at will. What a useful machine that must be to have!

*

Conclusions

Each teleportation model has its own little clutch of dangers, implications, ethical questions, obvious and non-obvious storytelling possibilities. I guess we already knew that. Teleportation can be central to a story or, if it wishes, it can — unbelievably — be entirely incidental.

It also seems that the existence of a working teleporter invariably implies the existence of one or more other fantastically powerful and dangerous technologies — disintegrators, momentum shunts, time travel. These other technologies often arise directly from teleportation science itself but equally often are simply separate, necessary prerequisites before any of this can work.

I wrote this mainly to clarify my own thoughts. I feel as if these are the primary colours. The next step is start mixing stuff up, like real stories do.

Back to Blog
Back to Things Of Interest

Discussion (50)

2016-06-24 00:13:24 by bbot:

Larry Niven's Known Space universe had teleportation booths that worked on the free exchange principle: https://en.wikipedia.org/wiki/Known_Space#Transfer_booths

He spent a couple stories working out the effects: https://en.wikipedia.org/wiki/Flash_Crowd etc etc

2016-06-24 01:05:32 by Mr. Eldritch:

There's another important distinction here - do teleporters "push", "pull", or both, and what (if anything) has to be on each end?

Like, Star Trek teleporters need only one non-portable machine, which can pull stuff from arbitrary locations to the machine, or push stuff from the machine to arbitrary locations.

Eve Online's jump drives can jump from anywhere using a portable machine they can carry, but they can only jump *to* locations that have a beacon ("cyno field") set up. The jump drive is doing the heavy lifting, the cyno's just there to give it a place to jump to.


So I suppose this set of distinctions would be which end (sending or receiving, or either, or both, or at some midpoint separate from either) the actual teleportation machinery needs to be on, and what if any secondary machinery needs to be on the other end. (Just a marker to designate it as a teleport location? Secondary machinery that can't send, but is needed to rematerialize a teleported target? Safety equipment to ensure the transportee arrives in good condition?)

2016-06-24 01:42:55 by ChanandlerBong:

Stargate actually does a printing type thing as well:
http://stargate.wikia.com/wiki/Stargate?action=edit&section=9&veaction=edit

2016-06-24 02:29:52 by Kp80:

I never understood the need to destroy the original in the "Printing" type of this. Do people hate the idea of a second "me" somewhere? Cory Doctorow handled it best in a short story.

2016-06-24 03:11:00 by Sunrek:

Stargate's Transporter Rings work on the Free-Exchange model. It's a little inconsistent, but for the most part it seems to be the case that the contents of each Ring Platform swap places.

Also, in addition to the Free-Exchange transfer booths, Lary Niven's books have "Stepper Plates." In "the Ringworld Engineers," the Velocity Conservation issue actually comes up, with plates too far apart on the Ringworld becoming dangerous to use. The traveler ends up arriving slightly charred if memory serves, as the difference in energy is expressed as heat.

Also, Halo uses the Orientation Conservation effect once as a comedic moment in the first game.

2016-06-24 03:50:00 by DanielLC:

Orientation conservation, like free exchange, has problems that aren't obvious at first. Under general relativity, orientation is a local property. If you move from A to B without turning, your final orientation will still depend on the path you take. This isn't a big practical problem though. It just means that the teleporter still technically has a path, even though nothing seems to move across it. Unless you have a really long range or access to a nearby black hole, you're not going to be able to take advantage of that to rotate objects during teleportation.

By extension, velocity conservation doesn't make perfect sense either.

In Harry Potter, teleporting makes a loud bang. This could be that it's crowbar teleportation, but I feel like that would be a lot louder than a gun. It could just be free exchange combined with slight differences in air pressure.

2016-06-24 04:14:13 by Fancybone:

Kp80: You should read "Think Like A Dinosaur", by James Patrick Kelly, for one potential reason why the original has to be destroyed.

This recommendation is neither an endorsement nor condemnation of the reasoning in the story.

2016-06-24 04:30:03 by Mozai:

In the venerable role-playing game "Traveller," they made attempts at making it hard sci-fi... despite having psionic supernatural powers. The "Teleportation" psionic power had a limit of distance and altitude because the psychic had to conserve angular momentum of the teleported object (usually the psychic, clothes optional). The only way to do the instantaneous acceleration for changing momentum like this was to gain/lose heat in the teleported object. So teleporting between two points at the same altitude and latitude was okay, but going to a different altitude or travelling north/south, and you risk giving yourself a fever or arriving with hypothermia.

2016-06-24 06:16:07 by Aucuparia:

Glasshouse is indeed an example of printing, and some of the ramifications of the existence of general-purpose matter printers (and how they can go wrong) is a pretty major plot point. It also includes wormholery.

One example of crowbar teleportation is apparition in Harry Potter. There's the distinct crack of air filling the vacuum left by disapparition, and a similar noise caused by air being force out of the way at the point of arrival.

2016-06-24 08:54:05 by Voidhawk:

There are multiple different methods of "appearing in a flash of light" in Stargate, many of which work subtlety differently to how they appear.

The titular Gate establishes a wormhole (through subspace), but it is microscopic and one-way. The rippling blue "puddle" is the event horizon of a matter-energy converter: it turns all objects that pass through it to a beam of energy, projects that beam through the wormhole, and the puddle on the other side reintegrates you. Since it is able to do this without any (noticeable) flaws, and you are entirely converted before the copy appears, it sidesteps most "Ship of Theseus" type arguments. Another factor is the inability to maintain a connection for more than 38mins (conveniently the length of an episode) without enormous power input, since the ends are moving relative to each other this puts tension on the wormhole. There have been some interesting episodes centred around what these effects mean, such as when a small spaceship got stuck half-way into an active gate, and the currently disintegrated half was *the half with the controls.*

The second most common method are Ring Transporters. A robust and mature design, these appear on first glance to be Free-Exchange teleporters, but are really a cleverly implemented version of disintegrator/re-integrators. When turned on they enclose an area at either end in floating rings, and whatever is at either end vanishes and is replaced with the other side. However, they have an elaborate activation sequence which is used as a distraction from what is actually going on: establishing a connection with the receiving set. Once a connection has been established it can time the two energy-streams to be dispatched at the same moment, pass each other, and arrive at an empty receiver. In the event that a passenger arrives prematurely or unexpectedly (a frequent occurrence), they are held in a buffer until the rings have finished activating and dispatched a return payload.

The third most common method are Asgard Beams, and they are the most powerful by far. Unlike the other methods they do not require the passenger to stand near a transmitter/receiver, simply moving an object from anywhere within their sphere of influence to anywhere else. The passenger is disintegrated for the duration of the trip, passing through subspace in a cloud of atoms before being reassembled. They seem to have a small crowbar effect on air at the destination, but are unable to beam a target into solid matter simply failing to send instead (and generating error messages), or beam through shields. Among other things, they have been used to: 1) beam nukes onto enemy ships, 2) beam an exploding office building into space, 3) beam people from one side of the USA to the other rather than take a plane, 4) beam a parasite out of someone's brain (required alot of calculation), 5) beam a grounded enemy fleet and army into nothingness, 6) be used with a CAD/CAM program to create a matter-replicator. Needless to say, they are one of the most powerful pieces of tech seen in the show.

2016-06-24 16:52:43 by hobbs:

In Philip K. Dick's _The Unteleported Man_ there's a group who are pretty sure that the government is running a fraud teleporter, but they're wrong. I think. It's hard to tell because it's PKD.

2016-06-25 23:38:25 by Carl Feynman:

With regard to teleporting and landing "on top" of an equal volume of air, it probably wouldn't be bad, as long as you didn't do it twice in rapid succession. Your body is already saturated with air at the pressure of the air around you ("ambient pressure"). We know from centuries of experiments on decompression sickness that it is dangerous to carry too much air in you body because it comes out of solution and the bubbles cause various colorfully named symptoms: the bends, the chokes, the staggers, etc. but we also know the limit below which symptoms do not appear. And that limit appears to be right around twice ambient pressure. If you fill your body with a double load of ambient pressure air, you'll probably be fine. You will gradually lose the extra air, over a timespan ranging from a few seconds for your lungs to more than a day for your cerebrospinal fluid and joint lubricant. If you teleport again during this period, you will be over the threshold of bubble formation and will start to bend, stagger, choke, etc.
All this assumes the arriving air molecules are allowed to slide gently in between your existing molecules and not jammed in willy-nilly.

2016-06-26 02:49:34 by Sam:

The printing model has a variant where you use quantum teleportation of a person's state, so you are not just incidentally destroying the original; the copying is impossible without destruction. Whether this still qualifies as murder may be left as an exercise for the reader.

2016-06-26 10:03:04 by traverseda:

> one who is unquestionably not the original.

Really depends on how you define "original", or whether or not the idea of original even makes sense in this context.

If you copy a file, and delete the original, and md5sum says that they're both the same, do you not still have the original file?

Something happens, but saying "original" is loading the situation with hidden inferences that may or may not make sense.

The point of this isn't that it is the original, the point of this is that you should remove the "unquestionably".

2016-06-26 10:52:17 by Mark Whybird:

Recommended relevant movie: The Prestige (2006). Look up a plot summary if you don't mind spoilers and want to know why.

2016-06-26 11:20:01 by Mark Whybird:

I've always wondered how teleport devices define the boundary of what they are teleporting. Some used closed booths, so you could then get away with taking the whole contents of the booth, but otherwise, while leaving clothes behind is comedic, it would be worse to leave your skin behind.

I've thought a lot about this, and I think perhaps the interface between the solids and liquids that make up most things we want to transport and the gasses (atmosphere) around them is important, which is why in the system I have in mind, you have to jump or fall (ie be airborne) to teleport - though internal gasses (notably in lungs, but possibly elsewhere in body - could cure the bends) is an issue.

Then there's the idea that the mass of what you are transporting is important... And inadvertently trying to transport someone/something that is touching the ground is effectively trying to transport the whole planet, and equipment shorts, or if it is a person rather than equipment, it feels like attempting to pick up Thor's hammer.

2016-06-26 13:54:30 by qntm:

> If you copy a file, and delete the original, and md5sum says that they're both the same, do you not still have the original file?

No, you have the copy, obviously. Like you just said, the original was deleted.

2016-06-26 14:06:56 by Omegatron:

It depends on if you subscribe to pattern identity theory or not. This comic (http://existentialcomics.com/comic/1) is relevant.

2016-06-26 17:09:19 by Voidhawk:

Atoms do not have "history", that is merely an artefact of human perception. There is no method of differentiating between atoms: indeed, the universe behaves as if such an idea is nonsensical. There is no such thing as "original" when it comes to arrangements, there is merely degrees of difference from a set reference pattern.

Certain changes can be more or less preferable of course. I wouldn't mind so much if a teleporter "ate" 1 gram of blood to use, but would issue many complaints if they left behind tumours. ("Question: I teleported bread!")

2016-06-26 18:29:17 by qntm:

> I never understood the need to destroy the original in the "Printing" type of this. Do people hate the idea of a second "me" somewhere?

It's not like both of us can live on the same salary.

2016-06-26 19:20:01 by brightlinger:

An example of crowbar teleportation might be the X-Men's Nightcrawler. His teleportation is always accompanied by the sound effect BAMF (at both source and destination), to indicate the sudden change in air pressure. Although he generally doesn't teleport into solid objects, and sometimes the story mentions that it would be a bad idea, so he might actually be using splice teleportation with a secondary power that has only limited ability to clear space for him.

2016-06-27 08:41:15 by Voidhawk:

>It's not like both of us can live on the same salary.
In a world where a machine can make an instantaneous copy of any object, accurately enough that organic creatures are both alive and indistinguishable from the orginal, economics is probably ruined enough to be beyond salaries. Either for good (everyone is free and has as much of anything as they want) or ill (everyone is slaves to the three guys who own the machine).

2016-06-27 12:56:31 by frymaster:

>In a world where a machine can make an instantaneous copy of any object, accurately enough that organic creatures are both alive and indistinguishable from the orginal...


.... you probably WOULD download a car!

But I'd get it from github. The engine would be more efficient and the sound system would kick ass, you just wouldn't get the "designer" badge of commercial offerings

2016-06-28 01:50:40 by dsm:

KP80: Of course I hate second me - he's a dick. He keeps trying to take all my stuff and have sex with my girlfriend.

2016-06-28 02:14:10 by Mark Whybird:

I've only read the free sample chapter of this, but it is an exploration of the economics of complete non-scarcity due to replicators that I actually might buy, despite not being an economist:
<a href="https://www.goodreads.com/book/show/27040338-trekonomics">Trekonomics: The Economics of Star Trek</a>. I recommend reading at least the free chapter :)

I also just spent about 30 minutes googling for a very old site that seriously explored how all of Star Trek technology could have been made fully internally consistent by simply starting with having planetary-distance teleporting... eg warp drive is just repeated teleportation of the entire ship. Can't find it though... anyone know the site I'm talking about?

2016-06-28 02:17:55 by Mark Whybird again:

For anyone with a mathematical/computer bent (i.e. qntm readers, probably), the books be Greg Egan https://www.goodreads.com/author/show/32699.Greg_Egan (hey! Look! he learned to read the note and not try to put html in!) are very cool - and in them, people being mostly software, the multiple-me issue/non-issue is explored several times.

2016-06-28 06:11:21 by Benjamin S.:

I'm partial to crowbar teleportation. The question of what happens when something less flexible than air is causing an obstruction seems clear to me; /so what/ if the destination space is obstructed? Think of it like trying to take a step forward i n our regular 3 dimensions, but instead of moving air out of the way you hit a wall. You just stop moving, no need for it to be a big deal.

Except instead of only banging your head into a wall, every atom in your body that overlaps the obstruction hits it and stops moving in that higher dimension. I if your arm is obstructed at the destination but the rest of your body has clear passage, one of three things could happen. 1) You're strong enough to deform / move the obstruction, to allow the passage of your arm into the space it occupies. 2) The rest of your body moves but your arm stays behind, kind of like 'splinching' in Harry Potter. 3) Imagine if you had your arms permanently outstretched and tried to pass between two posts that weren't far enough apart to pass through; the forces that hold all your atoms together prevents your body from moving without your arms; you don't get to go past the posts. and you stop. You might put strain on your body trying to move but realistically you won't do much harm to yourself if you're gentle.

The real thing to consider with crowbar teleportation is how much /pushy push/ your teleporter can generate in order to force you into place on the other side; you wanna make sure not to push too hard when met with resistance or Bad Things™ happen.

A weird thing to consider is like... If this form of teleportation is another dimension to travel in, another axis of movement, where space is not as... linear, what's the difference between pushing 5meters along that axis, and pushing 50? How do you know how far to push to get to the place you want to be at.

2016-06-28 06:43:08 by Ben:

Mark whybird, found it.

http://www.xibalba.demon.co.uk/jbr/tre
k/7.html

Magical teleportation is no Plane-walk either. Mlp fim fanfic has several different answers to that. "Blink", with destructive scan and copy, "dying to get there" with wormhole-ish properties, and estee's tryptych continuum, which hashes out the crowbar effect. thin or fragile solids can be telefragged, water is uncomfortable to displace, but it can be done, and attempting to jump to an already occupied space will cause random movement in any direction except down, until a sufficiently large volume is found.

2016-06-29 03:54:53 by Mark Whybird:

Thanks Ben! re-reading later today :)

2016-06-30 07:31:13 by Speising:

In the german pulp series Perry Rodan, the character Gucky can teleleport with a kind of crowbar type. He leaves a distinct clapping sound and produces a wind at the destination, but i don't know if the consequences of tp'ing into solid matter were explored.

2016-07-01 14:53:54 by Creaphis:

@Carl Feynman

There's still the potential that a sudden influx of air molecules in the exact wrong places could disrupt protein structures, cell membranes, etc. Plus, a single mote of dust overlapping with your brain could cleave through entire fibre tracts. Frequent customers of teleportation tech would suffer Alzheimer's-like symptoms in this case.

2016-07-01 15:01:34 by Creaphis:

In one episode of the X-men Evolution cartoon, Nightcrawler can't teleport from a plane to the ground because his power is velocity-preserving. I'm not sure if that's consistently the case or just a one-shot screenplay hack.

2016-07-02 03:59:15 by Mark Whybird:

Fun to be had with free-exchange TP:
1. teleport into smoke: person-shaped smoke cloud is visible (possibly inadvertently giving away target location of teleport). (If you use an enclosed booth, then the booth fills with smoke instead; same effect.)
2. assuming no booth, but that the air interface defines the edge, of the teleportee, teleport into rock for a perfect statue, even down to the hairs (though note that many hairs will immediately fall off, as rock lacks the tensile strength to weight ratio of hair. Also, rock commonly has micro-cracks in it already.)
 2.1. if the air interface defines the edge of what you can teleport, this is fatal, as you can't teleport out again. You may think you can teleport into a position where just your head is inside a roughly head-shaped piece of rock to make a perfect bust, and then have your friends or self smash away the remaining rock now encasing your head, but what about the air gaps in your sinuses that are now filled with rock?
 2.2. if the total mass of teleporting stuff is part of what determines the energy needed, then you can cap the energy input or 'feel around' exact target locations to prevent accidents like this... except:
   2.2.1. you could easily still be off by a little bit... if you wind up with even, say, a single finger (let alone hand) in a perfectly form-fitting, unyielding substance (rock, steel, whatever), can you escape without breaking your bones?
   2.2.2. if relative velocity change is also a factor in the energy required, you could be fooled by that

I always thought also that the distances would be quite limited, perhaps by requiring massively more energy to go far (inverse square/cube law?) or literal line-of-sight to the target (this is more for a magic, psychic version than a machine version, but could be adapted), and also that the transfer is speed-of-light; therefore there would be a very, very brief moment of hard vacuum in both places, which would definitely start to collapse ever so slightly in the case of transfer into air or, especially, liquid... resulting in.. maybe a weird tingling feeling in the skin as the interleaving effects (ranging from micro-fusion explosions, to physically ablating the extreme surface of the skin as things readjust) and perhaps elsewhere (tiny tiny quantum matter-antimatter explosions because of particle/antiparticle pairs having had time to spontaneously form in the vacuum); greater distances clearly exacerbate these effects due to the greater time lag.

Note, however, that I've still broken causality: if my transporter machine/person is at A, me staring to transport from A to B caused something (hard vacuum) to happen at B instantaneously. Perhaps my teleport device needs to be at the half-way point (whatever that means), or at least that nothing can start until light has had time for a round trip... hopefully nothing much has moved in that time... once again, distance is constrained.

2016-07-07 01:08:20 by Sean:

I once thought of a variant of free-exchange teleportation that preserves causality, at the expense (?) of introducing a "stasis" technology that stops the flow of time in some region of space, and also requiring (symmetric) machinery at both endpoints. It's somewhat inspired by quantum "teleportation" (which of course is not really teleportation at all, but has some similar features to this method). The idea is that something like this happens:

1) Region A and region B are both put into "stasis", not in any particular order. This implies that their contents are unobservable, since with no flow of time, they can't interact with the outside world.

2) Frozen regions A and B are synchronized with the assistance of some signal that travels at the speed of light (or slower). Each region is "treated" on its surface, using some information obtained from the surface of the other region (or physical entities, e.g. particles that have interacted with the surface of one region, which are then sent to the other).

3) A and B are "thawed" and resume the normal flow of time, their contents becoming observable again. When this occurs, B has the former contents of A, and A has the former contents of B, and the teleportation is complete.

Of course, this raises several new issues:

1) How "compatible" do regions A and B have to be, in terms of volume contained, velocity, and various typically-conserved quantities (energy, momentum, charge). What happens when there's a (mild or large) mismatch in any of those things?

2) What is the surface of one of these regions like? Is incoming light reflected, or simply absorbed and later released during the "thaw"? How is the synchronization signal created?

3) What happens if the synchronization process is incomplete? Specifically, what if A sends the synchronization signal to B (which is used as normal on B), but then A is "thawed" before the signal from B arrives? To preserve causality, we need one of the following sub-models:

a) Fancy printing: The "signal" is really a copy of all information needed to reconstruct a region, so this whole method is similar to printing, except that it uses some novel physics rather than nanotechnology to perform an atom-by-atom reconstruction. If the synchronization is incomplete as in the example above, the contents of region A are duplicated at both locations.

b) Destructive imaging: Similar to the above, except that when region A is thawed, it turns out to contain "garbage" (maybe plasma of approximately the same mass as the input). Once the signal is prepared for transmission to B, region A no longer possesses its original contents. This version avoids the problem of duplicating objects/people, and arguably is easier to justify with respect to physical principles such as conservation of information and the second law of thermodynamics.

c) Handshake: Each region has to send two signals, one at the beginning of the process, and a second after being "treated" using the first signal from the other region. If A is thawed before receiving the *first* signal from B, it contains its original contents (but B will never be able to receive those contents). If thawed after the first signal but before the *second*, it contains garbage. If thawed at the end of the process, it contains the contents of B (i.e. a successful teleportation). At this level of complexity, we can start to introduce some results regarding the security of the process (e.g., if A receives matter that's verifiably from B, this guarantees that there is one and only one copy of the contents of A, that it is an exact copy, and that B received it). Introducing even more signals could lead to arbitrarily complex variants on this idea.

d) Permafrost: Once a region begins the synchronization process, it becomes *physically impossible* to thaw that region until the process is complete. (Whether or not the process is complete before thawing must be agreed upon by all observers for this solution to work, so we need some kind of "handshake" to guarantee that observers near both A and B agree that they have completed synchronization.) This guarantees that we don't have to deal with the incomplete form of synchronization above; the teleportation process is always "pending" until successful completion. If the synchronization process can be attempted multiple times, then we effectively get an infinite number of "tries" to teleport a region. But if we can only attempt the process once for a given region, that means that it's possible to, for all practical purposes, permanently destroy the region of space, and everything in it. You simply start the teleportation process, then "throw away" some critical component or piece of information that would be necessary to complete the process.

2016-07-07 01:27:31 by Sean:

I suppose I should point out that if the "signal" in my free-exchange variant requires some kind of physical transmission of particles, and not just a complete copy of the classical *information* needed for reconstruction, then it probably counts as real teleportation rather than a just a weird form of printing.

But one of the interesting things about teleportation is that most methods imply a massive increase in the rate at which two locations can transfer information. If I could teleport a stack of hard drives to another continent (or planet!) once a second, that's obscenely faster than any (currently) conventional method for transmitting data. If I can do this by transmitting a handful of particles from one place to another, the effective data compression in that process is extreme.

2016-07-08 21:44:36 by JJJS:

Have you read Niven's "Theory and Practice of Teleportation"? Covers similar topics: http://www.e-reading.club/chapter.php/75689/7/Niven_-_All_The_Myriad_Ways.html

2016-07-12 06:22:14 by Evonix:

Of you make it inconvenient enough you could do it without affecting the rest of the place too much, need to spend power to equalize speed/gravwell and it not working otherwise, two ended, splice teleportation so the receiver needs to be in near perfect vacuum,the teleporters being big and slow enough that it would take months to teleport enough parts for a teleporter and so on, possible to do on a whim but not practical for most application beyond travel, supply of high value low mass goods, ect.

2016-07-15 21:31:00 by RainHappens:

> Some interpretations of this model hold that the inevitable result is a nuclear explosion, because the source atoms and target atoms end up close enough together for atomic fusion to occur. This... doesn't seem too likely to me? Atomic nuclei make up only a tiny fraction of a whole atom. And even if a few nuclei ended up genuinely interpolated into one another, creating a heavier nucleus and releasing some energy, why would that cause a chain reaction?

Some thoughts.

Let's say you teleport a cube of iron into another cube of iron. Classical nuclear radius of iron is ~4.6 * 10^-15 m. So each cube of iron is ~3.5 * 10^-14 nucleus (~3.5 * 10^-12 %). Simple stats indicate that you'd end up with ~the corresponding %age interposing. Working it out, it'd end up with ~3*10^9 atoms interposed per cubic cm. Not much at all, really. mJ of energy at maximum. Mind you, that could be a half-decent way of making some isotopes. Take a chamber full of gas or liquid at a high pressure, and repeatedly teleport one half of the gas into the other half. In practice you'd probably want a heat exchanger in the center, as otherwise you'll melt the chamber.

The bigger problem would be *chemical* effects. Or rather, electro-repulsive ones. You've effectively just compressed the iron to double its normal density. This has a *lot* of potential energy. Read: kJ / cm^3, if not more. Easily enough to vaporize said iron. (It'd be as though you teleported a chunk of the Earth's core.)

So it wouldn't be a nuclear explosion, scale-wise - but it would be bad nonetheless. And I think you underestimate just how bad it'd be - even teleporting into air would be fatal. There are enough spots where a rogue air molecule *wouldn't* be accepted to cause... problems. You'd (briefly) end up with two atmospheres of pressure inside, and one outside - oddly similar to sudden vacuum exposure in some ways. Lung damage, etc. 14.7 pounds / square inch is no fun at all. (Also: you'd die of a pulmonary embolism, even if nothing else killed you.) And every dust particle in the air would cause localized damage.

Which also begs the question of where that energy came from. It'd "have to" be supplied by the teleporter, unless you want to throw conservation of energy out the window too.

2016-08-03 05:21:10 by Miëtek:

> Atoms do not have "history", that is merely an artefact of human perception. There is no method of differentiating between atoms: indeed, the universe behaves as if such an idea is nonsensical. There is no such thing as "original" when it comes to arrangements, there is merely degrees of difference from a set reference pattern.

Just because we don’t have such a method doesn’t mean we cannot conceive of such a method, especially in a fictional setting. Consider the universe as a virtual machine: the virtualisation platform has the opportunity to inspect its memory will, taking as much time between ticks of object-level time as it requires, and distinguishing between patterns indistinguishable from within the virtual machine by tracking their spatio-temporal coordinates.

2016-08-03 05:21:59 by Miëtek:

s/memory will/memory at will/

2016-08-16 00:07:47 by FeepingCreature:

Count me in camp "Printing teleportation *damn well* is teleportation".

To me the notion of a 'copy' of a mind isn't even coherent; my mind is a pattern, not a particular set of atoms.

This is basically just the uploading debate again anyways.

2016-09-04 23:34:55 by dmytry:

For the causality issue with the swap teleporter... you could introduce a preferred reference frame.

If you go 1 year into the past and 10 light years away, you won't be able to come back and tell yourself not to take the trip, unless you come back via another teleporter that doesn't move you 1 year into the future (the way your original teleporter would).

If the swap teleporters always work instantaneously in one preferred frame of reference (e.g. coincident with universe's "at rest" as determined by observing doppler effects on the microwave background), while they do travel in the past according to other frames of reference, they never pass anything into it's past light cone.

2016-09-06 18:45:22 by BillMann:

Although not technically teleportation, The Long Earth Series uses some sort of Crowbar effect for stepping and if you try and "step" into something, you just can't, you bounce back.

2016-09-10 21:26:35 by Matulraz:

Note about the X-Men's Nightcrawler. He doesn't technically teleport, he uses "Wormholery" to jump into a Hell-dimention, where spatial laws don't quite match up with our own, and back. I believe the smoke he leaves behind with every jump is supposed to smell like brimstone!

2017-04-05 14:37:01 by Almonaster:

For a detailed exploration of the velocity conservation variant, try "Witling" by Vernor Vinge.

2017-05-17 16:36:39 by Aegeus:

Schlock Mercenary has a blend of Printing and Wormholing with its Teraport. They can't open a wormhole big enough for a whole object, so they use trillions of tiny wormholes instead. Disassemble the object, move the pieces, and reassemble.

("So you call it a 'tear-apart'?")

2017-11-13 14:16:59 by Tahrey:

*skips a rafts of comments that are almost certainly fascinating and may already contain this idea but will take about an hour to read*

One that seems to be missing: paired booths that *don't* exchange matter, but maintain vacuum within them. Preferably more like spherical rooms than booths, with antigravity and intertial compensators, to allow for orientation issues and reference frame velocity differences.

Teleportation is between two fixed points and requires that the location has already been reached by conventional means at least once. Also, the items being teleported have to be happy with exposure to hard vacuum and zero-gee. Lifeforms or other objects that require an atmosphere would have to be contained within some kind of environment suit or other protective structure *which is teleported along with them*; similarly any requirement for sustained gravity would have to be taken care of by the container.

It's a small modification to the Niven or Star Trek type, but one I feel is A) more realistic, B) more practical, and, moreover, C) much safer for all involved. No thunderclap of displaced or suddenly-missing air, no potential atomic annihilation, no biological shock at being momentarily exposed to the hammer-blow (if you'll excuse me stealing that term from Best Thing Since Sliced Bread, as I re-read it only a few hours ago) of zero / double (or more) air pressure. Etc, etc.

A slightly different variation would be allowing teleportation to or from some other abitrary point, but only if at least the destination and preferably both ends were fully or near-hard-vacuum, i.e. reasonably far into interplanetary space that the number of already existing particles per square metre wouldn't cause a serious issue, or maybe using an evacuated-to-the-limit pressure vessel on a planetary surface as a last resort. Don't know how you'd receive, place, build, and intertially correct the teleporter signal into an arbitrary position (maybe you wouldn't even be able to do a very good job of the latter, or not do it at all, which would be a caveat of such emergency-evac use; the protective container for any non-inherently-rugged items would have to pick up *that* slack as well, cushioning them from the worst of any impact forces), but that's a possible handwaveable.

For example moving a ship between two points in deep space at light speed (or faster if using a subspace layer where the value of c is much higher) - both start and end are near-vacuum, and the ship counts as the environment container. Either can use free-space teleportation, or gigantic "booths" that are essentially a type of stargate. Fly in a ship of anything up to certain maximum dimensions (larger ones could possibly break up into individually transportable modules), choose from a preset list of destinations, hit the button, *ZWUMV*, appear some time later (but instanteously by your own perception) in the booth at the other end, and make a prompt exit. Obviously signal reception, buffering, routing, would be rather crucial in case you had two attempted transmissions arriving at the same time. Possibly some serious handshaking or just plain old fashioned early-days-of-the-railway style timetabling for each possible link combination (and use of high capacity backbones and repeaters to keep the number of links per node to a sensible level) would be required.

And as suggested above, you could even do an emergency (heck, even a routine) beam-out from a volume where nothing was likely to be damaged or significantly disturbed by a sphere of material surrounding the object of interest also being transported and thus suddenly going missing, which would cause a localised implosion anywhere pressurised to a meaningful level. Full thundercrack and all that. Wheel of Time, maybe, if I'm remembering right? Or Terminator, certainly. On arrival into the vac'd destination, the surrounding material (mostly air, maybe some soil or rock, in most instances, if you've picked a sympathetic place to beam from) would just dissipate/float away if in space, or ultimately fall to the floor/mix with the incoming air repressurising the booth if in a purpose built facility.

The dangerous thing would be beaming *in* to such an environment, even if *from* hard vacuum, because, as you mention, there's all kinds of problems with potentially supra-luminal outward expansion/explosion of the existing material, or it being annihilated (LOTS of energy release!) or ending up integrated with your own somehow - ignoring the all too convenient but physically problematic "exchange" idea. Essentially banned under all but the absolutely most extreme circumstances, limited to a considerable minimum distance from inhabited areas, protected nature reserves or sensitive industrial/military facilities, and pretty much counted as a type of WMD with all the sanction that comes along with any use of such unless you have high-level prior organisation or can prove that Needs very much led to Must.

2017-11-13 14:19:07 by Tahrey:

* inertially correct, even (instead of intertially) ... my barely-concealed dyslexic issues showing through a bit there due to a lapse in the deliberate conscious examine-and-correct routines. Thought I'd got all of them...

2017-11-13 14:38:35 by Tahrey:

Alternative to the routing issue, also - have them work rather like the old pneumatic capsule money / message transport tubes of yore (still seen in some supermarkets...).

Each booth is directly linked to only one other. They're always installed in matched pairs. Quantum-entangled, maybe, for an extra sprinkle of exotica (there's a question - what happens if you teleport one half of an entangled pair of particles? FTL communication possible? Or would we ultimately find that changes of entangled state also take finite, c-bounded time to propagate, we just weren't measuring them carefully enough at first?). So the complexity limit becomes how many such booths you can manufacture and practically install at any one site, and long distance teleporter travel becomes more like moving freight around on the railways ... a series of smaller jumps between major interchange nodes, maybe in a queue at the more popular ones where they just can't build and install additional parallel chambers fast enough... and if you're headed somewhere a bit remote and unpopular, maybe having to take a bit of a roundabout route with the final jump being into a single slightly rickety T-booth shared by your destination and several of its neighbours, then some hours or days (or more?) of onward conventional travel.

Oh and of course, in opposition to the real world air tubes, each one would normally have to be one-way to avoid conflict because of how long it would otherwise take to handshake a transmission. If each link is unidirectional then the transmission can essentially be completely unmediated and the receiver just sits there waiting for any arbitrary incoming signal to appear from the matched transmitter (which opens up some nice potential storylines for hijacking the signal... unless link patency and security was maintained by them continually sending a teletype-style idle-ack or ring-network style token back and forth between each other).

So they'd normally be installed in pairs of pairs... two transmitters, two receivers, with one of each at any given site. Maybe with a fallback mode to allow bidirectional transfer on a timetabled basis, or even with very long-winded handshaking (only really practical with jumps that are less than a light-day apart, so you could organise a teleport within maybe half a week, avoiding a week or more of conventional thrusting to get around the breakage), kind of like cosmic roadworks with traffic lights or stop-go boards ;-) ... with the loss of the aforementioned keep-alive signal eliciting an exasperated sigh from the T-network managers ... "oh, not again... dammit, Bernice, nodelink 5473-7728 has fallen back to bi-di for the third time this year, you think we're EVER going to get that thing working properly?".

The alternative being of course a big problem in that it might work in one direction but not the other, which if it's a great enough distance effectively means you're stranded on an outer space desert island, and it'll take years or decades to get back to civilisation if no-one sends through the parts and an engineering crew to fix it. Could even be done deliberately through sabotage, or with specific one-way links for waste disposal or even as an alternative to normal prisons. Punish your wrongdoers by putting them in a ship that has all the things needed to sustain life, but only a conventional interplanetary drive on board, and T-jump them far enough out from the main network, through a one-way gate, that means their sentence is served on that ship whilst making their way back in-system. Their choice then whether they do that, or go off to prospect new worlds at sublight speed, or top themselves, or go rogue and prey on new arrivals (just part of the punishment, the risk of being attacked by pirates - for the duration of your sentence, you are a literal outlaw), whatever.

AKA, turn the failure of your fancy futuristic device to be a universal panacea into a plot generator instead. The more interesting artworks always seem to come from interacting with the limits, rather than being unlimited...

Right, I think that's my head emptied on this one.

2017-11-13 14:43:16 by Tahrey:

Oh aye. Just realised that what I've described there is essentially fibre optic networking between backbone switches (either inside corporations, or through the shared WAN), so there's certainly precedent for that kind of long distance "information" transmission. Just... massively scaled up. And the switches that the fibre lines connect into are essentially the terminus nodes, which would become the deep space equivalent of mainline train stations.

(Has anyone actually done a sci-fi series - book, TV, whatever - that focusses on such a place? I mean, there's B5 and DS9, but they're more waypoints, halfway-house stagecoach inns, rather than proper transport hubs... even when we consider the presence of a jump gate near to one of them... it's a single, multi destination device. I'm thinking a setup rather more like the powerstrip in Wreck-It Ralph... and I can't think of anything more literary than those two relatively pulpy TV shows...)