The Dungeons & Dragons Antiteliphone

[Totema]

Oh my god, what happened to all these poor catgirls!?

[DigoDragon]

How does that work with physics?

It's sort of like you folded space-time in such a way so that your starting and ending points overlapped. Then you unfolded it, remaining on the end point. No distance traveled.

Oh my god, what happened to all these poor catgirls!?

Pah, that's what Nekomancers are for.

[mathmancer]

First, big shout out to Mewtarthio. He not only understands it, he seems to understand the physics behind it better than I do!

I was thinking of this scenario earlier:

You are on Earth and your friend is on Mars. For the argument, let's assume the distance between the two planets is such that at the speed of light, the travel time will be 12 minutes. You send a message to your friend using a beam of light. The message asks your friend to send you back a package by way of a Teleport spell. Your friend receives the message 12 minutes after you sent it. He messages back that he's sending the package and teleports the package over at the same time.

From your perspective, you sent the message and after 12 minutes you receive the package. 24 minutes after you sent your message, you receive the reply that the packing is on it's way.

The package circumvented the distance. From you and your friend's perspective nothing seems all that odd (You did get a 12 minute delay between receiving the package and your friend's response, but that's to be expected because the message had to travel the distance while the package did not). From the package's perspective, it left with your friend's reply, but got to it's destination first by about 12 minutes because it skipped the transit part of the trip.

It still causes a paradox, because we're taking the "now" for granted. Your friend gets the message 12 minutes after you send it. He teleports the package to you. The package arrives "now" but... when is "now"? from HIS frame of reference, and from YOUR frame of reference, those may mean very different things. From his perspective, the package reaches you "now", so that (with a strong enough telescope, or maybe a scrying spell), he could watch you receive the package 12 minutes after you sent the message to him (from HIS perspective). For you on the other hand, the package wouldn't arrive 12 minutes after you sent the message. I can't actually predict when it would arrive for you, not without knowing what your Frame of Reference actually IS, but the package may arrive 12 minutes before you send the first message (because in your frame of reference, the sequence of events got flipped), or you may even receive the package an hour after sending the message.

I'm finding out, as I read more about it, that a frame of reference isn't strictly limited to a geographical location. Two frames of reference may occupy the same point in space. A frame of reference is sort of like a super confusing way to rephrase that "an object in motion stays in motion". It's turned it into "a point of view in motion stays in motion". So, depending on the relative velocity of ALL points of view (sadly, not just yours, or else I might be able to make sense of all of this), that package will get back to you at an unpredictable moment. With this in mind... I can't even say for certain distance is required anymore. You may be able to invoke causality breaking paradoxes by teleporting to a spot in the same room (maaaaybe)!

This STRONGLY suggests that the teleport spell has a time delay built into it (which has been suggested many times by many people already in this thread). In a sense, we could even add a new rule to the games magic mechanics: "All spells obey relativity". We might even have to, because as BRC says, there are a LOT of ways to bump into the anti-telephone if that rule isn't there.

Spoiler: MATH HERE

Show

I would like to propose a way for calculating an arrival time with a 1 plank time delay.

(d / C) + 1pt

d=distance, C="the speed of light", and pt=plank time
This would be the smallest possible delay without creating an anti-telephone for ANY magical effect.
Using the sending spell to talk to some one a light second away? It'll appear to get there 1 second late.

Planes make things weird though. As Red Fel pointed out, the Astral Plane is timeless. There is no "time travel" spell that I know of in the core books, but it's not inconceivable, within the context of d&d, that travel through the Astral Plane could be exploited magically to cause time travel (and at that point, arriving at an interstellar destination earlier than you could if you traveled at a sub-light speed would just be gravy to an effect that already collapses all of science into a flaming ruin).

Problem: my friend is on mars. I am on earth. The data I send goes through the entire planet, across barriers designed to block light and electric signals, and my friend receives tem in his nested bunker of airtight and signal-proof anechoic chambers wherein there is no possible line of effect for instantly-fast travel to actually make the transition from.

He still gets it, because it stepped outside of space.

How does that work with physics?


Teleportation doesn't go in straight lines very fast; if it did it would be useless (well, "useless"). Teleportation says "the closest distance between two points is literally no distance at all and I am already there".

Well, with physics, the scenario you described still invokes the anti-telephone. Even if you found a way to block gravity (lets just tack on an anti-gravity spell to your scenario) you are still spatially connected to the rest of the universe. I have to apologize actually, because I was confused about the use of the word "observer" by physicists. Physicists basically mean "frame of reference" when they say "observer", which isn't what most people (including me in the earlier parts of this very thread) think of when we think of an "observer".

BUT. Lets adjust your scenario even more. Lets say your friend is in a pocket dimension. By using a spell, you create a demi-plane on Mars, and instead of using teleport you use a spell that OTHERWISE behaves exactly like a teleport spell, except it also includes planer travel (I believe gate does that, but I'm being fast and loose and not looking it up, and may even have the spell name wrong). Now, your friend is like Shrodengers cat so far as your friends state is unknowable by science (but it wouldn't actually be running into a Quantum Mechanics problem, so your friend isn't TRULY like the cat. Your friends wave function is collapsed whether we see it or not, there just isn't a way for US to see it... at least I think that's how it works. QM is sort of a competing theory to relativity so I'm really hesitant to predict anything with regards to QM).

IN THAT CASE, causality would still be preserved depending on the state they are in when they leave the demiplane and return to Mars. If, for ALL cases when they leave the demiplane before 12 minutes, AND they have not received your message or magically teleported any packages back to you, then causality is fine. In all other cases, causality will go on the fritz.

Teleport does not move you, it circumvents distance. It specifically messes with space, not speed or anything.

It's sort of like you folded space-time in such a way so that your starting and ending points overlapped. Then you unfolded it, remaining on the end point. No distance traveled.

And none of those qualifications have bearing on the d&d anti-telephone either. As discussed, folding space in exactly the way you describe, still leads to time travel (and all the paradoxes that THAT implies).

You may have seen the edit I made to the original post, because this keeps coming up. The big confusion here is that people believe I'm equating teleport with superluminal velocities when i say that it's a form of FTL travel, or that I'm some how suggesting that some one is changing their velocity in some way. For that reason, I added a quick little comment at the very beginning of the thread that, I hope, will clarify every thing.

I sort of have to apologize in some way. I really just wanted to present an interesting Case study about d&d's magic, but it turned into this huge THING where we argued about physics. To every one, I want to say that I'M SORRY!

I still plan on making more threads like this one. Just talking through it all, I learned a LOT about relativity because i forced myself to understand things in order to respond to every one. I just hope future threads will be less confrontational.

[Segev]

I only have an M.S. in Physics, not a Ph.D., but I did study relativity and this sort of phenomenon. The OP is correct: teleportation across sufficient distance that you would notice that you'd beat the light from where you started to where you wound up would result in anti-telephone type effects.

One of the easiest illustrations I can give without drawing diagrams (always the physicist's friend) is this: Everybody is at least colloquially familiar with the idea that relativistic speeds cause time to slow down for you. That's a gross oversimplification, and is actually reciprocal. We'll rely on this for our example, because I want to put us as the experimenters in this thought experiment on our hypothetical rocket ship.

The faster the rocket goes, the more we'll see the rest of the universe slow down from our perspective. If we could, due to magic, actually achieve the speed of light, we'd see the universe literally stopped. For light - the only thing actually capable of moving at c in reality - there is no time. A photon exists at every point in its trajectory simultaneously from its perspective, and all is static.


This phenomenon produces a truth we know of as the "light cone" in relativistic discussion. If a flashbulb goes off at the moment of an event, the light will travel at c away from that event. When it reaches the location of your detector, you "see" the flash and know the event occurred.

We are only able to meaningfully establish causal relationships between things which occur "within" each other's light cones. That is, two events happening can only establish a "before" and "after" when observed from a point in time and space where their light cones overlap.

To illustrate, if you conduct the measurement at a point of space-time wherein the two light cones exactly intersect, such that "before" on whatever timeline you're using is outside of either of them and "after" on the same timeline is within both, the two events appear to have happened simultaneously. The relativistic effects of variable reference frames can cause your personal timeline to instead intersect them such that one occurs before the other. Picture, instead of a line passing through the nexus where the two cones meet, it passing through to the right or the left, so that it "sees" one first and then the other.

Now, recall that the speed of light is as fast as information can go. You can't have a steeper timeline than following the light-cone's edge exactly. The more your timeline arrow is tilted to the right or the left, the closer to the speed of light you're moving. If you tilt so far that you pass from inside the cone to outside, you're going to see the event "unhappen" instead of happen - this is backwards-in-time-travel. It's why "going faster than light" is said to also be going backwards in time.

Note, from our "move the timeline left or right" example, that you can choose by virtue of where you place the timeline which event appears to happen first. Since you can only measure simultaneity from the perspective of a reference frame that is within both light cones of the two possibly-simultaneous events, if you're at a point in time and space that is outside of either of them, you can't tell if the other has occurred "yet."

This isn't some foolish "just because you can't see it doesn't mean it didn't happen" thing, either. If you're in a different reference frame, you will see their timing (even if you use back-calculation to determine "real" timing based on the speed of light) as different, because the perpendicular intersection with your timeline will be different that with somebody else's in a different reference frame.

...and this all is why diagrams are so important. >_< This is probably very confusing.

All of this to say: if you teleport from one point to another "instantaneously," you create two events which, in theory, are simultaneous: your disappearance from one point in space (and time) and reappearance at another point in space (and time...though notionally, you're at the same point in time). The problem is that the notion that these events are simultaneous requires that the reference frame be the same in both locales. If they're not, we now need to decide whether you magically adopt the new reference frame as well as the new location, or not. If you teleport from shore to floating ten feet above a boat, are you stationary wrt the boat or wrt the original shore? If you teleport from one boat to another, and they were moving different directions, do you retain momentum from the original boat and risk falling over, or is the new boat's momentum now yours without any need to transfer force?

This is important if you consider, say, teleporting from Earth to a colony on Mars. Again, let's assume magic is involved, so we can arbitrarily set our rules for how it works.

Since Greater Teleport actually takes us any distance, let's set ourselves up as teleporting from one end of the galaxy to the other, between two ships moving on whatever courses they like.

• If we assume that we retain our old reference frames, we (very briefly, before turning to a smear of strawberry jelly on a ragged hole through the hull of the destination vessel) are moving at relativistic speeds at the other end wrt the destination vessel. This causes observational problems all its own.
• If, on the other hand, we assume that we take on the new reference frame, we get the behavior we expect, notionally, from teleporting from one place to another: we appear at the other end and are stationary wrt it.

Let's assume we go with the latter, as it "feels" more like what we expect when somebody uses magical teleportation to galavant across the galaxy.

Remember how moving at different speeds makes our timeline "lean" in different directions relative to other reference frames, and how this causes a simultaneous event in one reference frame to be non-simultaneous in another? Well, now you've moved between two RADICALLY different reference frames. Whereas, in the highly tragic first bullet point, we at least know that the two events were simultaneous in the timeline of the reference frame we occupied before and (very briefly) after teleporting, the second bullet point doesn't afford us that luxury.

But, let's say that the magic is such that it prefers the starting point's reference frame, and uses that to determine simultaneity. So when the light from your arrival event arrives at your origin point, it will indeed seem (calculating backwards for how long it took light to reach from your destination back to your origin) that it happened simultaneously.

When the light from your origin point reaches your destination, however, an observer back-calculating the same information wrt light speed and distance will determine that the two events were not simultaneous. It's possible that it would determine that they happened such that you left, then some time passed, and you arrived...but it could also turn out (depending on the relative speed and direction of the two frames) that the destination sees you as having arrived before you left the other side.

Normally, such observations don't happen because the speed of light is such that information cannot get from one point to another faster than light...and in all reference frames, light arrives at a destination after it leaves its origin. How soon after will vary and contain disagreement, but it always will be causal.

Having gotten from one place to another faster than light, however, different reference frames will disagree on whether you arrived or left first.

So, let's say you teleported between the two frames as described, magically assuming the destination frame's reference when you got there so no messy deaths occur and you can have meaningful interaction with the people on your destination starship. So far, not a big deal; you're the only point of contact between them and so it seemed simultaneous to you, so things seem fine.

Unfortunately, two events which are measured as simultaneous in the destination reference frame when they happen at your destination and at your origin will also appear, at your origin, to have the event at the destination frame happen AFTER the event at your origin frame.

Let's say that the skew is such that, if you waited for the light to arrive and calculated backwards, you would determine that you arrived at your destination 10 minutes before you left your origin point, at least as far as your destination frame of reference is concerned.

This means that an event that your destination would say happened simultaneously there and back at the origin would, on the origin ship, seem to have happened 10 minutes after it occurred on the origin ship.

So...what happens when you teleport BACK from the destination to the origin? You arrive, from the perspective of the origin to which you're returning, 10 minutes before you left the destination. If you stayed for only one minute at the destination, this means you arrive back at your origin 10 minutes before you left to arrive at the destination in the first place.