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mathmancer
2014-09-29, 08:02 PM
EDIT:please read most of the thread before posting.

Also, I am NOT, nor was I ever, stating that Teleportation is the same thing as motion through space (you'll see what I DO mean if you read through the thread though). No where do I state that any kind of motion at all is necessary. All you need (still) is special relativity, and the teleport spell.

And that's the end of the Edit. The rest is the unedited post in its entirety:

Hello every one! My first post on the forum.

I was reading the "Ultimate guide to the tippyverse" thread. It started out by reading that atomic rockets web page. Atomic Rockets mentioned that FTL would ALWAYS result in time travel and the break down of causality. "But how?" I wondered. I had to think back to what little I know about General relativity (I'm a laymen, and I wont claim to be otherwise). I vaguely remembered how, in essence (Again, I'm a real physics laymen, so I have to throw in lots of qualifiers), relativity states that all observers have to see the same thing. Is that what atomic rockets meant? If some one traveled faster than the speed of light, they would APPEAR to arrive at the destination before they left the source. Since it would appear like that to some observers, it would appear that way to all observers. So in effect, the traveler would go back in time.

It turns out, that was pretty close to what actually happens. Then I stumbled onto a Wikipedia article that affirmed that that's more or less how it works. I stumbled into it because I remembered that Tachyons were a theoretical particle that is FTL (and therefore travels backwards through time). That lead me to the Wikipedia article on the Tachyon anti-telephone. I wont repeat it here, but I highly encourage you all to read it to see what I'm talking about.

So, to finally relate this to d&d, I realized that teleportation (as the spell) of any kind is essentially Faster Than Light Travel. It might not screw with causality very badly when teleporting around the same planet, because the distances are so small. You only travel back in time a fraction of a second (a time that could be expressed in plank times). But what about when you're traveling on one of those outer planes that continue infinitely in every direction (like Arcadia)?

Then there are some other strange possibilities. Spelljammers are also a good way to teleport. If a ship with a spelljammer helm found an area in the material plane that is a few light years across, it could teleport back and forth until it goes far enough back in time to do... well whatever it wants. This allows a LOT of screwy things.

1.Some one could use this to solve p=np and crack hard encryption.
2.Time travelers from a future that NEVER TAKES PLACE can start appearing (or even invade).

If THE spelljammer (that giant manta with a city on it's back) discovered such an area in the material plane, and could willfully exploit it, that would explain why the spelljammer is so hard to find. But then you have the fact that a continuous civilization (if not one continuous nation) that lives LONGER THAN THE UNIVERSE ITSELF is riding on the spelljammers back. And you wouldn't know which tech level you would encounter either. If a party encountered the spelljammer twice, they might find a civilzation equal to the d&d level of tech, or they might find a civilization that has been developing technology for trillions of years.

This is all a thought exercise I've been working on, and I wanted to share it with all of you, because I realize it would have LARGE implications for the Tippyverse. It's compatible with ANY d&d edition (you just need a teleport spell to exist). It's also the source of the big bad evil guy in my next game.

The bbeg is actually going to be one of the good guys, except they are from a future that never comes to pass, because the bbeg was evil all along and has been exploiting the teleport spell to alter history. Since the history of the world is a result of the bbeg's meddling, no one's even aware the past was ever different. So the bbeg is an ancient spell caster with access to super high tech.

Even knowing that, there are all kinds of SHOCKING REVEALS in the story as the players unravel all of the bbeg's impact on history. ("Ok, you knew the bbeg is the reason the Human empire fell, but did you also know that..... the bbeg IS JIMMY'S CHARACTERS FATHER?!"..... eh, you get the idea.)

I actually hope to create a few more threads about how, with a basic understanding of physics, you can exploit even some "harmless" spells or magic items to completely change society.

Beleriphon
2014-09-29, 08:55 PM
Hello every one! My first post on the forum.

I was reading the "Ultimate guide to the tippyverse" thread. It started out by reading that atomic rockets web page. Atomic Rockets mentioned that FTL would ALWAYS result in time travel and the break down of causality. "But how?" I wondered. I had to think back to what little I know about General relativity (I'm a laymen, and I wont claim to be otherwise). I vaguely remembered how, in essence (Again, I'm a real physics laymen, so I have to throw in lots of qualifiers), relativity states that all observers have to see the same thing. Is that what atomic rockets meant? If some one traveled faster than the speed of light, they would APPEAR to arrive at the destination before they left the source. Since it would appear like that to some observers, it would appear that way to all observers. So in effect, the traveler would go back in time.

Okay, I looked it up. It hurt my brain. I'm a bright guy and I don't often admit this, but damn that really hurts my brain.


It turns out, that was pretty close to what actually happens. Then I stumbled onto a Wikipedia article that affirmed that that's more or less how it works. I stumbled into it because I remembered that Tachyons were a theoretical particle that is FTL (and therefore travels backwards through time). That lead me to the Wikipedia article on the Tachyon anti-telephone. I wont repeat it here, but I highly encourage you all to read it to see what I'm talking about.

Does this involve getting messages from yourself from the future? If it doe sI want no part of those shenanigins.


So, to finally relate this to d&d, I realized that teleportation (as the spell) of any kind is essentially Faster Than Light Travel. It might not screw with causality very badly when teleporting around the same planet, because the distances are so small. You only travel back in time a fraction of a second (a time that could be expressed in plank times). But what about when you're traveling on one of those outer planes that continue infinitely in every direction (like Arcadia)?

Teleport isn't FTL though, its more like a worm hole, or exploiting the three dimensional nature of the universe.


Then there are some other strange possibilities. Spelljammers are also a good way to teleport. If a ship with a spelljammer helm found an area in the material plane that is a few light years across, it could teleport back and forth until it goes far enough back in time to do... well whatever it wants. This allows a LOT of screwy things.

1.Some one could use this to solve p=np and crack hard encryption.
2.Time travelers from a future that NEVER TAKES PLACE can start appearing (or even invade).

If THE spelljammer (that giant manta with a city on it's back) discovered such an area in the material plane, and could willfully exploit it, that would explain why the spelljammer is so hard to find. But then you have the fact that a continuous civilization (if not one continuous nation) that lives LONGER THAN THE UNIVERSE ITSELF is riding on the spelljammers back. And you wouldn't know which tech level you would encounter either. If a party encountered the spelljammer twice, they might find a civilzation equal to the d&d level of tech, or they might find a civilization that has been developing technology for trillions of years.

This is all a thought exercise I've been working on, and I wanted to share it with all of you, because I realize it would have LARGE implications for the Tippyverse. It's compatible with ANY d&d edition (you just need a teleport spell to exist). It's also the source of the big bad evil guy in my next game.

The bbeg is actually going to be one of the good guys, except they are from a future that never comes to pass, because the bbeg was evil all along and has been exploiting the teleport spell to alter history. Since the history of the world is a result of the bbeg's meddling, no one's even aware the past was ever different. So the bbeg is an ancient spell caster with access to super high tech.

Even knowing that, there are all kinds of SHOCKING REVEALS in the story as the players unravel all of the bbeg's impact on history. ("Ok, you knew the bbeg is the reason the Human empire fell, but did you also know that..... the bbeg IS JIMMY'S CHARACTERS FATHER?!"..... eh, you get the idea.)

I actually hope to create a few more threads about how, with a basic understanding of physics, you can exploit even some "harmless" spells or magic items to completely change society.

I just say crib from any Doctor Who plot that makes use of time travel as a major plot. I'd personally avoid using Newtonian phyics within anything approaching D&D styled magic, the two just don't really mix. Quantum physics for all of the theoretical stuff that could happen might as well be magic so mix away.

Cazero
2014-09-30, 03:52 AM
Teleport isn't FTL though, its more like a worm hole, or exploiting the three dimensional nature of the universe.

Basically this. Teleport time-altering paradoxes can be handwaved away by the fact that teleport might not rely on FTL travel. Instead, it uses multidimensional travel through spatial dimensions unreachable without magic to push the teleported item on a very short distance.
To better understand how this works, this video (http://www.youtube.com/watch?v=uDaKzQNlMFw) might help. Now, imagine that nothing limits you to 4 dimensions. You could have 5, 6 or even more accessible via magic, allowing to connect any 3D point in our universe to any other 3D point in the same universe, or a different set of 3 dimensions (aka a different plane), via a very short nD path.

But if you want to use teleport-FTL time travel shehanigans in your setting, nothing stops you from doing so. After all, both methods are valid way to reach another place instantly.

mathmancer
2014-09-30, 07:28 AM
Teleport isn't FTL though, its more like a worm hole, or exploiting the three dimensional nature of the universe.

Its true that you aren't, within your local frame of reference, moving any faster than normal. That's not actually important for relativity though (as far as I can tell). You mentioned worm holes, for example. Wormholes, and ansibles(another scifi artifact) are also often used by physicist in thought exercises exploring this exact same break down of all causality. Wormholes are often used as a convenient way to go back in time, because they can do it the brute force way.

But one version goes like this: You have a wormhole between two solar systems that are maybe 1 light year apart (but, surprisingly, they don't have to be that far apart at all). The two ends are "linked" to the same time (within all frames of reference), but then they "drift" apart. Eventually the two ends are hundreds of light years apart. You run into the exact same problems that Tachyons do. Objects that enter the worm hole at the source, will arrive at the destination before they leave. Even stranger, you will have the same effect in both directions, so a round trip will only take you further back in time.


Instead, it uses multidimensional travel through spatial dimensions unreachable without magic to push the teleported item on a very short distance.

Nope. Unless the spell says you're using multidimensional travel, you're still in 3d space (as much as anything is. Again, I wont pretend to be anything other than a laymen, but I can't quite understand the connections between 4d and teleport).


I just say crib from any Doctor Who plot that makes use of time travel as a major plot.

*rolls a 1 on nerd lore* I have never watched Doctor Who.


I'd personally avoid using Newtonian physics within anything approaching D&D styled magic, the two just don't really mix. Quantum physics for all of the theoretical stuff that could happen might as well be magic so mix away.

au contraire! It's the perfect place to mix Physics (though in this case, not NEWTONIAN physics. Pretty sure Einstein and his contemporaries were the ones who figured out the relativity('s). Unless Newton DID understand general and spacial relativity and was holding out on us? But I digress ). Unlike a Tachyon, the teleport spell doesn't travel FTL within it's medium (you'll probably want air), so no nasty Cherenkov radiation killing every one. EVEN BETTER: because it's magic, because it's SUPER natural, and not natural, you don't invalidate the usual laws of the universe (you violate them, but you don't invalidate them). In this case, I'm using the word "natural" the same way they do when saying words like "natural history" and "super natural" and "natural philosophy", to mean "without magic" or as the archaic way of saying "physics". In a d&d world, we can easily say that physics work the same way they do here, in real life. Things just get muddled when wizards and dragons start screwing every thing up with magic. If it wasn't for them literally CHEATING THE LAWS OF THE UNIVERSE, causality and relativity would be true ALL the time. Another way of saying it is: the rules of physics are still the same, we just have people using magic to ignore them.

If we found a way to do the things the teleport spell does, but without some supernatural means, then we would have to re-write all of physics. But since teleport is only possible through a mage, or monster, or magical trinket, and can't be reproduced by physics (that we are aware of. oh so many qualifiers), then physicists have nothing to do with teleport (except where it can aid them in learning about the universe, but they don't need to tack it onto the standard model or anything).

A mage who happens to discover another planet (through scrying) or is on an infinite plane, could even discover relativity accidentally if they take a round trip, or a couple round trip.

Alternatively, they could learn more about the teleport spell itself. They description in the phb (any edition) is brief. That's fine. If wizards were to get some lawers and physicists involved, each spell description would fill a library. It just wouldn't be fun. But narrative-ly it could be a source of story. Say they find out that the teleport spell isn't ACTUALLY a teleport spell, and that it always takes you some place at the speed of light. In such a case, the spell only breaks the laws of thermodynamics (like that's some small thing), but not relativity, or causality.

I always wonder why mage's don't go on to explore space, and one explanation is that teleport only takes you to your destination a moment after the light from the source arrives there. Mages teleporting interstellar distances mysteriously "disappear" never to be seen again, because it takes them a decade or longer to make a round trip (if they even accounted for having no atmosphere or hyper gravity, or all of the crazy things that could kill them before they can return). Then, as natural philosophy catches up, every one realizes what had happened to all of those wizards who teleported too far, and they realize that a NEW spell would need to be "invented" to achieve the effect they wanted. This "superluminal teleport" spell might then be invented, but would be a distinct spell from "regular teleport" (Jack Vance fans will jump on the chance to make a name like "Evards Awesome Translocation" or some such).

This also makes the whole thought experiment similar to Leplace's Demon (if you're familiar with that one), in that magic is being used to exploit the rules of physics without working within their constraints.

All that being said..... don't just SPRING THIS on your DM. You'll be THAT GUY instantly. Talk to your DM before you screw up causality.

AGH! Look at how little it took to get me to post so much!

TheCountAlucard
2014-09-30, 09:07 AM
Mathmancer, pretty much all the teleport spells explicitly express the fact that the teleportation magic works via shunting yourself through the Astral Plane.


A teleportation spell transports one or more creatures or objects a great distance. The most powerful of these spells can cross planar boundaries. Unlike summoning spells, the transportation is (unless otherwise noted) one-way and not dispellable.

Teleportation is instantaneous travel through the Astral Plane. Anything that blocks astral travel also blocks teleportation.


If I have a circular racetrack that is 1.1 light-seconds long, and observe that the finish line is right there by where the starting line is, and so turn around when the starter pistol goes off and cross the finish line in a second, I didn't really travel faster than the speed of light - I just took advantage of a shorter route.

Effectively, the Astral Plane is the shorter route to everywhere.

Ettina
2014-09-30, 09:23 AM
Teleportation isn't faster than light travel, it's taking a shortcut through another dimension.

mathmancer
2014-09-30, 11:23 AM
Teleport isn't FTL though, its more like a worm hole, or exploiting the three dimensional nature of the universe.




Teleport isn't FTL though, its more like a worm hole, or exploiting the three dimensional nature of the universe.
Basically this. Teleport time-altering paradoxes can be handwaved away by the fact that teleport might not rely on FTL travel.


Teleportation isn't faster than light travel, it's taking a shortcut through another dimension.


Mathmancer, pretty much all the teleport spells explicitly express the fact that the teleportation magic works via shunting yourself through the Astral Plane.




If I have a circular racetrack that is 1.1 light-seconds long, and observe that the finish line is right there by where the starting line is, and so turn around when the starter pistol goes off and cross the finish line in a second, I didn't really travel faster than the speed of light - I just took advantage of a shorter route.

Effectively, the Astral Plane is the shorter route to everywhere.

Every one seems to be getting hung up on the fact that the persons velocity (yes, velocity), within their frame of reference, isn't actually super-luminal.

I'll admit I didn't read the spell description very closely, but it still doesn't really have any effect.

I should make a distinction here between FTL Travel and FTL velocity.

FTL Velocity: your Delta-Position is greater than C (the speed of light) at any moment (don't invoke Zenos Paradox please. The burden would be on you to show why people actually ARE in motion).

FTL Travel: You arrive at the destination BEFORE the light cone of your departure. This includes all the sci-fi tricks. Wormholes, Hyperspace travel, Alcubiera drives, Stargates (a manmade wormhole... according to the shows lore), Jump drives, Spelljammer helms, using the Astral Plane as a shortcut, using ANOTHER UNIVERSE as a shortcut, Spice Navigators from Dune who will you to the other end of the universe without moving, Warp Travel (Like in warhammer 40,000), Quantum Tunneling, Laplaces Demon, and more.

The key here is when the light catches up to you.

Example: Planet A is 10 light years from Planet B. Melf starts on planet A. Melf uses SOMETHING to go to Planet B. No matter how he did it, if he arrives at Planet B any sooner than 10 years, he has just traveled back in time and violated causality. If he arrives 10 years exactly or later, causality is just fine.

Teleport is used in the case of my d&d anti-telephone concept, but if you really think about it, there could be a variety of spells that do this. You could even exploit Sigil (THE CITY OF DOOOOOOOORS) and just find portals to two places on the material plane sufficiently far apart (as long as those portals behave consistently enough for you to reliable exploit them).

TheCountAlucard
2014-09-30, 11:36 AM
So what you're saying is that by teleporting to a remote enough location on the same plane - some pretty vast distances involved here for it to be worth trying - you could look at the light from events that happened in the past of where you were prior to the teleporting. Correct?

Considering how even with a clear line of sight with no obstructions, at those distances we can't really see much in detail - it'd take effort to notice a planet exploding - I don't see how this is remotely useful on its own, even assuming that you're doing this on a plane that has these remote distances and know exactly where and when to look. You might as well ask about a spell to scry into the past - it does the same thing, without you having to survive extra-perilous environment and also develop a means of seeing back across all that distance.

Besides, there's also a distance cap and a miss chance on Teleport, and if you're high enough in level to have reliable access to the greater teleportation spells, then you're pretty much already capable of spreading causality across a bagel like cream cheese and eating it for breakfast.

mathmancer
2014-09-30, 11:52 AM
So what you're saying is that by teleporting to a remote enough location on the same plane - some pretty vast distances involved here for it to be worth trying - you could look at the light from events that happened in the past of where you were prior to the teleporting. Correct?

Considering how at those distances we can't really see much in detail - it'd take effort to notice a planet exploding - I don't see how this is remotely useful on its own, even assuming that you're doing this on a plane that has these remote distances and know exactly where and when to look.

You've almost got it. For the purpose of physics, you observe things whether or not you're cognitive of it. An observer can only indirectly see things some times. There aren't any microscopes that can see something smaller than an atom, but we still observe the macroscopic effects of atomic physics all throughout life. You don't have to have a microscope and watch your cesium atoms as they touch water in order to ensure they still react and explode.

In the same way, if the traveler is making a round trip, the observer at the destination will see this effect. In the example I gave with my games bbeg. The bbeg is from a future THAT NEVER HAPPENS. In the context of that story, the observers are the player characters who are being antagonized. They don't need to have any direct observations of the bbeg's journey across the stars, they just need to have a time-invader harassing them.

edit: sorry, I forgot something else. On the macroscopic scale, you don't have to worry about collapsing quantum wave states (little known fact(fiction)= Shrodenger owned a cat that was smaller than one photon). I know the rules of relativity I mentioned use an observer, but as far as I can tell (again, physics laymen), that's not strictly necessary. In the case here, the event is simply appearing the same to all POSSIBLE observers in ALL POSSIBLE frames of reference.

Fiery Diamond
2014-09-30, 12:18 PM
Every one seems to be getting hung up on the fact that the persons velocity (yes, velocity), within their frame of reference, isn't actually super-luminal.

I'll admit I didn't read the spell description very closely, but it still doesn't really have any effect.

I should make a distinction here between FTL Travel and FTL velocity.

FTL Velocity: your Delta-Position is greater than C (the speed of light) at any moment (don't invoke Zenos Paradox please. The burden would be on you to show why people actually ARE in motion).

FTL Travel: You arrive at the destination BEFORE the light cone of your departure. This includes all the sci-fi tricks. Wormholes, Hyperspace travel, Alcubiera drives, Stargates (a manmade wormhole... according to the shows lore), Jump drives, Spelljammer helms, using the Astral Plane as a shortcut, using ANOTHER UNIVERSE as a shortcut, Spice Navigators from Dune who will you to the other end of the universe without moving, Warp Travel (Like in warhammer 40,000), Quantum Tunneling, Laplaces Demon, and more.

The key here is when the light catches up to you.

Example: Planet A is 10 light years from Planet B. Melf starts on planet A. Melf uses SOMETHING to go to Planet B. No matter how he did it, if he arrives at Planet B any sooner than 10 years, he has just traveled back in time and violated causality. If he arrives 10 years exactly or later, causality is just fine.

Teleport is used in the case of my d&d anti-telephone concept, but if you really think about it, there could be a variety of spells that do this. You could even exploit Sigil (THE CITY OF DOOOOOOOORS) and just find portals to two places on the material plane sufficiently far apart (as long as those portals behave consistently enough for you to reliable exploit them).

No.

FTL Velocity is what FTL Travel means. You and a beam of light departing from point A and you arriving at point B before the beam of light does does not mean that you have traveled back in time. When light catches up to you is utterly irrelevant. Explain to me, entirely in non-physics terms, how going faster than C and folding space are at all the same. The racetrack analogy is spot on. Explain how it isn't. For example... assume we have a racetrack that looks like this...

||===============A=================||
||xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx||
||===============B=================||

Where the track is follows the double lines (the || and =). xxxxx is an area where light cannot travel due to the fact that it is another dimension or similar - light is forced to follow the path of the track. The race begins at point A and proceeds in either direction to point B. The track is long enough that if we cross the other dimension from A to B, we arrive faster before light along the track does. In what way have we traveled back in time?

Red Fel
2014-09-30, 12:19 PM
Let me start by saying that, as others have mentioned, if this is how you want to run your campaign, nobody's stopping you, and I happen to think it sounds like fun.

That said, I think you're making an assumption. Let me illustrate a situation, and then I'll get to that assumption.

Now, you opened the thread with a situation in which a person travels faster than light, and therefore appears to arrive at his destination before he left, and therefore actually arrived before he left, and therefore traveled through (an infinitesimally small amount of) time. Fine. You then go on to observe how the same holds true of D&D-style teleportation, which is extradimensional via a universally coterminous plane. Let's examine that scenario. Ulric the Wizard is in the Deserts of Hotendrai. He casts Teleport to leave that horrible place and return to his home in Kuhlendahmp. One standard action later, Ulric vanishes into the Astral. Ulric reappears in the Material, in (or close to) Kuhlendahmp.
Now, as I understand you, your assumption is that, like FTL, teleportation results in the person being objectively observable at his destination before he leaves his starting point, and therefore that he has in fact arrived before he departed. I'm not sure that teleportation supports this, for several reasons: Relativity is based upon motion through space. It does not, to my recollection, presume the existence of instantaneous transit, such as teleportation. Applying the one to the other seems a bit tenuous. The passage of time is more complex in a multiplanar cosmology. Note that the Astral was originally written as a slow-time plane, with years passing on the Astral for each day on the Material; it was updated to be a timeless plane, meaning that time does not actually pass while traveling in the Astral. In effect, this turns relativity on its head; ages can pass for Ulric, who will emerge precisely when he departed. Physics fails in a D&D setting. Try to model an explosion. Or calculate pi. Or determine an object's terminal velocity or the damage it can cause while falling. Physics fails.
As a final point, I'd like to note that all observers do not see the same thing. The classic example is the "lightbulb on a train" problem (http://www.phys.vt.edu/~takeuchi/relativity/notes/section09.html). (I make no guarantees for quality; I grabbed the first example I could find.) You have three parties - one fixed to the ground, one fixed to the train car, and one moving faster than the train car. At a certain point, the one on the train car turns on a light in the train. Each one observes the light reaching the different parts of the train in a different relative frame. That's how relativity works. The light does not move differently based on what each one sees; rather, the idea is that the passage of time (e.g. before and after) is dependent upon the observer; it is not objective.

In other words, the fact that one observer sees Ulric arriving prior to his departure (and I'm still not quite sure how we got to that) does not mean that he actually arrived prior to his departure; rather, it means that he arrived prior to his departure relative to that observer.

... And now I'm giving myself a headache...

Steel Mirror
2014-09-30, 01:04 PM
You could also say that teleportation isn't actually instantaneous, it is rather nigh-instantaneous, and in fact allows travel at velocities approaching the speed of light. That is so damn fast that it makes no practical difference to anyone using the spell, but prevents major head trauma from trying to understand causality and tachyon spellcraft.

Or you could rule that light does, in fact, travel instantaneously in your D&D universe, making the issue a non-issue. Or that physics is wacky in some other way.

Of course, if what you really want is to have fun with combining D&D spells and real world relativistic physics in fun ways just for the sake of seeing where it takes you, have at it!:smallwink:

Sith_Happens
2014-09-30, 01:12 PM
... And now I'm giving myself a headache...

TL;DR: The OP is arguing that an event hasn't occurred from your frame of reference until you've had the chance to see it happen. This is empirically false (see: astronomy and cosmology).

SiuiS
2014-09-30, 03:58 PM
Teleport does not move you, it circumvents distance. It specifically messes with space, not speed or anything.

mathmancer
2014-09-30, 04:51 PM
You could also say that teleportation isn't actually instantaneous, it is rather nigh-instantaneous, and in fact allows travel at velocities approaching the speed of light. That is so damn fast that it makes no practical difference to anyone using the spell, but prevents major head trauma from trying to understand causality and tachyon spellcraft.

Or you could rule that light does, in fact, travel instantaneously in your D&D universe, making the issue a non-issue. Or that physics is wacky in some other way.

Of course, if what you really want is to have fun with combining D&D spells and real world relativistic physics in fun ways just for the sake of seeing where it takes you, have at it!:smallwink:

That's actually exactly what I suggested in one post. I love you forever.

Anyways, the HARDEST posts to respond to are actually the ones that ask the "simplest" questions. I'm struggling with Fiery Diamonds post right now. I'm trying to answer it, but the most difficult demand he made was "Explain to me, entirely in non-physics terms, ...." but he's asking me to explain Relativity of Simultaneity....... that's not an easy thing to do EVEN WITH gobs of equations and fancy physics jargon. I'm really struggling to find away to break it down.

I wanted to respond to you though, because we basically agree, and it's easier. I will get to every one else though.

Steel Mirror
2014-09-30, 05:35 PM
That's actually exactly what I suggested in one post.Haha, sorry, I can see that now. I read through the previous posts, but I was clearly skimming a bit, and missed that on the first readthrough. :smallredface:

As for questions like Fiery Diamond's question, yeah that is difficult. This link (http://www.askamathematician.com/2012/07/q-how-does-instantaneous-communication-violate-causality/) explains some of the issues with defining "instantaneous" and reordering causality that happens in different inertial frames of reference once you introduce faster than light transmission of information (whether by moving at 10x c or by taking shortcuts), but unfortunately it doesn't quite fulfill the criteria of "entirely in non-physics terms", which is difficult...

DigoDragon
2014-09-30, 06:31 PM
Teleport does not move you, it circumvents distance. It specifically messes with space, not speed or anything.

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.

BRC
2014-09-30, 07:07 PM
Poking around, I found a quote that FTL Communication is just as bad here as FTL Travel, for the same reasons.
So, assuming the Teleport trick works, Sending should work just as well.

You have a contact on a distant planet. You use Sending to give them a message, they Send a message back, you receive that message in the past.

Fiery Diamond
2014-09-30, 07:29 PM
In other words, the fact that one observer sees Ulric arriving prior to his departure (and I'm still not quite sure how we got to that) does not mean that he actually arrived prior to his departure; rather, it means that he arrived prior to his departure relative to that observer.

Exactly.


TL;DR: The OP is arguing that an event hasn't occurred from your frame of reference until you've had the chance to see it happen. This is empirically false (see: astronomy and cosmology).

Yeah. Precisely.


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

QUOTE=DigoDragon;18189295]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.[/QUOTE]

Right.


Haha, sorry, I can see that now. I read through the previous posts, but I was clearly skimming a bit, and missed that on the first readthrough. :smallredface:

As for questions like Fiery Diamond's question, yeah that is difficult. This link (http://www.askamathematician.com/2012/07/q-how-does-instantaneous-communication-violate-causality/) explains some of the issues with defining "instantaneous" and reordering causality that happens in different inertial frames of reference once you introduce faster than light transmission of information (whether by moving at 10x c or by taking shortcuts), but unfortunately it doesn't quite fulfill the criteria of "entirely in non-physics terms", which is difficult...

...I'm reading that link and it's actually making a surprising amount of sense. The thing is, this all has to do with motion through space, which is precisely what teleporting is not. Furthermore, I'm reminded of a particular xkcd what-if. (https://what-if.xkcd.com/37/) The song is not being played backwards, even if that's how you perceive it.

...

I've finished reading the link. (That qualifies as entirely non-physics terms to me, by the way, or close enough.) Hm. I think I see the problem. When presupposing teleportation as circumventing distances rather than traveling them instantaneously, we tend to automatically assume that the two frames of reference - here and there - are NOT moving with respect to each other. If the here and there are both static with respect to the other, you don't run into the time travel shenanigans.

The trick is that in calling it a circumvention of distance rather than traveling, we ARE violating the basics of relativity: as the link said, that all reference frames are equal. They aren't if we have circumvention of distance. We have a meta-frame which is static to all other frames, and it is this frame that forms are medium of teleportation. In other words, two frames not static to each other are also at the same time static to each other for the purposes of teleportation. We're not violating causality, we're violating a completely different aspect of reality: mutually exclusive things are both true. We're breaking relativity by brute-forcing all frames of reference to be treated as static with respect to each other, even if they aren't.

Steel Mirror
2014-09-30, 07:47 PM
The trick is that in calling it a circumvention of distance rather than traveling, we ARE violating the basics of relativity: as the link said, that all reference frames are equal. They aren't if we have circumvention of distance. We have a meta-frame which is static to all other frames, and it is this frame that forms are medium of teleportation. In other words, two frames not static to each other are also at the same time static to each other for the purposes of teleportation. We're not violating causality, we're violating a completely different aspect of reality: mutually exclusive things are both true. We're breaking relativity by brute-forcing all frames of reference to be treated as static with respect to each other, even if they aren't.If you want an absolute reference frame in order to describe your D&D physics, I would suggest looking into the luminiferous (http://en.wikipedia.org/wiki/Luminiferous_aether) aether (http://physics.about.com/od/physicsitol/g/LuminousEther.htm). It is one of my favorite defunct theories, which stated in essence that space is pervaded with an invisible substance (or is made of this invisible substance) called aether, through which light propagates in a manner reminiscent of how waves ripple across the surface of a pond. In an aether based cosmology, there is an absolute frame of reference, the frame of reference of the aether itself. Objects moving through the aether at some velocity might observe events in different orders compared to other frames of reference, but you can always resolve any apparent inconsistencies by referring to what the aether frame observes; it is authoritative. Then you can brush any tachyon shenanigans under the rug (unless you want them to happen).

Plus aether is such a good word to dust off for your D&D campaign, it lends that veneer of Victorian credibility to any arcanist's mad mutterings about his teleportation time travel theory. :smallsmile: ("THEY CALLED ME MAD! MAAAAAD!!!)

SiuiS
2014-09-30, 07:54 PM
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.

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".

mathmancer
2014-09-30, 08:17 PM
I will try to answer this in order.

No.

FTL Velocity is what FTL Travel means.

Alright, well it will only get more confusing if we start arguing somantics at the same time we argue physics, so I'll make another attempt to find some common language. That IS what you are objecting to with that statement right? Because if not... then you're defeating your own argument (are we arguing?)

By the transitive property, if a=b and b=c then a=c. in this instance, a would be FTL Velocity and b would be FTL Travel. By what I just quoted above, you're statement is a=b.

By what I said:

FTL Velocity: your Delta-Position is greater than C (the speed of light) at any moment (don't invoke Zenos Paradox please. The burden would be on you to show why people actually ARE in motion).

FTL Travel: You arrive at the destination BEFORE the light cone of your departure. This includes all the sci-fi tricks. Wormholes, Hyperspace travel, Alcubiera drives, Stargates (a manmade wormhole... according to the shows lore), Jump drives, Spelljammer helms, using the Astral Plane as a shortcut, using ANOTHER UNIVERSE as a shortcut, Spice Navigators from Dune who will you to the other end of the universe without moving, Warp Travel (Like in warhammer 40,000), Quantum Tunneling, Laplaces Demon, and more.

FTL Travel (b) = set C{Wormholes, Hyperspace travel, Alcubiera drives, Stargates (a manmade wormhole... according to the shows lore), Jump drives, Spelljammer helms, using the Astral Plane as a shortcut, using ANOTHER UNIVERSE as a shortcut, Spice Navigators from Dune who will you to the other end of the universe without moving, Warp Travel (Like in warhammer 40,000), Quantum Tunneling, Laplaces Demon, and more}

so by the transitive property, FTL Velocity = set C.

Which would mean that you're saying FTL Velocity = teleportation. But since that's what you're arguing against, then you clearly don't mean that when you say


No.

FTL Velocity is what FTL Travel means.

So we need to find some common language, because we ARE talking about two different things. That's what I was trying to do when I made the distinction between the terms FTL travel and FTL velocity, but I suppose I failed at that. So now I have to come up with a term or word for what I'm describing, which is just about any way of arriving at your destination sooner than what is, by the current known theory of physics, possible.

If I was to name a catagory that included teleportation, hyperspace, wormholes, and simply having an FTL Velocity, and more, but not use the name "FTL Travel" for that catagory.... well... I guess it can't be a name that describes the catagory then. Lets just call it CATAGORY DS. an item in CATAGORY DS would be a form of CATAGORY DS travel. DS is for Doc. E.E. Smith, a scifi author known for writing space opera. The methods of space travel in a space opera will always move at the speed of plot(that's a joke).

Continuing this, that means that FTL Velocity is one item in CATAGORY DS, but it is not the only one. Another item in CATAGORY DS is teleportation.

The logical statement (not the equation or phenomena those equations describe) would be:
If an item appears in CATAGORY DS, then that item breaks causality.

And it is, apparently, my burden to show that that logical statement is true (I will, keep reading).

I'm trying to clarify things, because your statement revealed that I needed to be more explicit, but I'm afraid that by being more explicit and technical I'm also being more confusing.


You and a beam of light departing from point A and you arriving at point B before the beam of light does does not mean that you have traveled back in time. When light catches up to you is utterly irrelevant.

This is, I must concede, technically correct. But only because light will travel slower within a medium. So there ARE times when you could travel slower than C, but faster than the beam of light, and you would NOT travel back in time or mess with causality. I am partially to blame here, because I was being lose with my terms earlier. I will continue to make such mistakes, even willfully, because I'm trying to explain it easily and I'm still a laymen myself.


Explain to me, entirely in non-physics terms, how going faster than C and folding space are at all the same.

They are very different methods, I will agree, but they both violate causality. I'm assuming (and I know it's bad to assume) that when you say "folding space" you're folding space in order to achieve the same end result as the teleportation spell. I also have to assume that you don't want me to simply "explain...(how those things)... are at all the same" because that's open ended enough to let me say something like "Because they're both not real!"(a joke, come on lighten up people!). So now I have a bigger assumption. I'm assuming you want me to show how moving faster than C and folding space BOTH result in causality violating time travel.

So, hoping I have guessed your INTENT correctly, here is my attempt at doing what I believe you have challenged me to do (Oh god the number of qualifiers I have to use to dance my way through every sentence is getting unbearable!) I can restrict myself to non-physics terms, but I can't explain very much that way. Here's my best attempt:


How moving faster than C and folding space BOTH result in causality violating time travel.


The principle of causality is fairly straight forward. According to causality, if there is some effect which is produced by some cause, then the cause must precede the effect. So, if for some observer (in some frame of reference) an effect truly happens before its cause occurs, then causality is violated for that observer. Now, recall our discussion in Section 1.1 concerning when occurrences happen in a frame of reference. There I took a moment to explain that when I talk about the order of events in some frame of reference, I mean their actual order, and not necessarily the order in which they are seen. One can imagine a situation whereby I could first receive light from the effect and later receive light from the cause. However, This might be because the effect is simply much closer to me than the cause (so that light takes less time to travel from the effect I observer, and I see it first). After I take into account the time it took the light to travel from each event, then I will find the order in which the events truly occurred, and this will determine whether or not there is a true violation of causality in my frame. This true violation of causality is what I will be talking about, not some trick concerning when observers see events, but a concept concerning the actual order of the events in some frame of reference.

Ok, so this explains more or less what causality is, and how, depending on where you are and what you're doing you can start to see some strange things.

Also, incidentally, I see now that I WAS confusing the concept of an "observer". I thought it all WAS a trick on observing things out of order, but Dr. Hinson just explained that Relativity goes a lot.... DEEPER than light tricks.


I refer you back to Diagram 2-9 (reproduced below as Diagram 8-1 ) so that I can demonstrate the causality problem involved with FTL travel. There you see two observers passing by one another.

Diagram 8-1
(Copy of Diagram 2-9)

http://www.physicsguy.com/ftl/figures/xptp.gif

The origin marks the place and time where the two observers are right next to one another. The x' and t' axes are said to represent the frame of reference of O' (I'll use Op--for O-prime--so that I can easily indicate the possessive form of O as O's and the possessive form of O' as Op's). The x and t axes are then the reference frame of the O observer. We consider the O system to be our rest system, while the Op observer passes by O at a relativistic speed. As you can see from the two coordinate systems, the two observers measure space and time in different ways. Now, consider again the event marked "*". Cover up the x and t axis and look only at the Op system. In this system, the event is above the x' axis. If the Op observer at the origin could look left and right and see all the way down his space axis instantaneously, then he would have to wait a while for the event "*" to occur. Now cover up the Op system and look only at the O system. In this system, the event is below the x axis. So to O, the event has already occurred by the time the two observers are passing one another.

Normally, this fact gives us no trouble. If you draw a light cone (as discussed in Section 2.8 ) through the origin, then the event will be outside of the light cone. As long as no signal can travel faster than the speed of light, then it will be impossible for either observer to know about or influence the event. So even though it is in one observer's past, he cannot know about it, and even though it is in the other observer's future, he cannot have an effect on it. This is how relativity saves its own self from violating causality.

However, consider the prospect of FTL travel with this diagram in mind. As O and Op pass by one another, the event "*" has not happened yet in Op's frame of reference. Thus, if he can send an FTL signal fast enough, then he should be able to send a signal (from the origin) which could effect "*". However, in O's frame, "*" has already occurred by the time O and Op pass by one another. This means that the event "Op sends out the signal which effects *" occurs after the event which it effects, "*", in O's frame. For O, The effect precedes the cause. Thus, the signal which travels FTL in Op's frame violates causality for O's frame. Similarly, since "*" has already occurred in O's frame when O and Op pass one another, then in his frame an FTL signal could be sent out from "*" which could reach O and tell him about the event as the two observer's past. However, for Op, the event "O learns about * as O and Op pass one another" comes before * itself. Thus, the signal which is FTL in O's frame violates causality in Op's frame.

In short, for any signal sent FTL in one frame of reference, another frame of reference can be found in which that signal actually traveled backwards in time, thus violating causality in that frame.

Notice that in this example I never mentioned anything about how the signal gets between the origin and *. I didn't even require that the signal be "in our universe" when it was "traveling" ( remember our definition of FTL travel). The only things I required were that (1) the signal's "sending" and "receiving" were events in our universe and (2) the space-time between the origin and "*" is flat (i.e. it is correctly described by special relativity diagrams). Some FTL ideas may invalidate the second assumption, but we will consider them a bit later. We will find, however, that violation of causality still follows from all the FTL travel concepts.

Alright, so this is where Dr. Hinson explains how regular FTL Velocity violates causality. Interestingly, he makes the same distinction I did between FTL Velocity and FTL Travel.... but I only mention that to help people understand what he's talking about.

Lastly, as Dr. Hinson promised:

9.3 "Folding" Space (Without Special Provisions)

Another concept which pops into the minds of science fiction lovers when considering FTL travel is that of "folding" space. Basically, the idea is to bring two points in space closer together in some way so that you can travel between them quickly without having to "actually" travel faster than light. Of course, by our definition of FTL travel in Section 6.1 (where the light you are "racing" against goes through normal space between the starting and ending points) this would still be considered FTL travel.

A frequently used approach for picturing this idea is to think of two dimensions of space represented by a flat sheet of paper. Then consider yourself at some point on the paper (call this point "o"). If you want to travel to some distant point ("D"), you simply fold/bend/crumple/etc the paper and place "o" and "D" close to one another. Then its just a matter of traveling the now short distance between the points.

Again, we see an FTL concept which is built in order to get around the problem of the light speed barrier. However, we will see, once again, that the second problem of FTL travel is not so easily fixed.

We begin to understand this when we consider again the sheet of paper discussed above. Every object in that two dimensional space has a place on the paper. However, because objects may be moving, their position depends on the time at which you are considering them. Basically, if you are sitting at "o", you imagine every point on that sheet of paper as representing space as it is "right now" according to your frame of reference. However, as we have discussed, what is going on "right now" at a distant location truly depends on your frame of reference. Two observers at "o" in two different frames of reference will have two different ideas of what events should be represented on the paper as going on "right now". This difference in simultaneity between different frames of reference is what allowed for the "unsolvable paradox" problem to exist in the first place. Thus, even though you "fold" the paper so that you don't "actually" travel faster than light, you don't change the fact that you are connecting two events at distant points (your departure and your arrival) which in another frame of reference occur in the opposite order. (In the other frame of reference, you aren't just bending space, you're bending space-time such that you travel backwards in time.) It is that fact which allowed the unsolvable paradoxes to be produced.

In the end, unless special provisions are present, one can use this form of FTL travel in our FTL bullet example (I refer you back to the listing of events in Section 8.3 ). Op will fold space in his frame of reference to connect the passing event with the event "*", while the third observer will fold space from his frame of reference to connect the event "he sees the victim die" with an event "O learns of the victims death before the FTL bullet is sent". Thus, you can used this method to produce an unsolvable paradox as we discussed earlier.

And that's where Dr. Hinson explains how folding space will still create gross violations of causality. And by virtue of that, Teleport, which involves NO MOTION AT ALL, still belongs to the set CATAGORY DS.

I have to apologize. I don't have a Doctorate in Physics. I can't do very much better than "That's what physicists say happens". Dr. Hinson isn't some crackpot Doctor with a shady online degree either. Dr. Hinson isn't even explaining his own theory, he's just describing the implications of theorys that were developed by Einstein and Einsteins contemporary called the theory of Special Relativity and the theory of general Relativity.

Unlike me, Dr. Hinson can do a little bit better than "Hey, that's just what Einstein says ok?", but I can't get him to re-write his webpage to fit your demand for non-physics terms, and I don't know enough about how it works to explain it in simpler terms than he does. really I don't understand it at all, I just understand the conclusions of "FTL = time travel" and "Teleport = FTL too!"

On that note, if you're smarter than I am (which is not at all unlikely), i encourage you to read Dr. Hinsons page at http://www.physicsguy.com/ftl/html/FTL_part4.html#sec:ftleqvofc
I also encourage you to not just take HIS word for it, and to do your own indipendant research. To get you started, check out

Relativity of Simultaniety. That's a good term to research. Don't just settle for wikipedia's page on it either.
Closed Timelike Curves (CTC). Also relavent, but you'll see how every one who believes these to exist are also scrambling to figure out how to preserve causality.
If you can read German (I can't) try reading the publications of the original physicists! Einstein, Heisenberg, Godel, and a few others all wrote stuff relevant to what I'm failing to explain here.
Also, check out http://www.projectrho.com/public_html/rocket/fasterlight.php It's about nuclear space ships, and it mostly just uses the same links that I did, but like me he's trying to relate the implications of physics to literature


This probably does a better job of showing what happens if you make a "Dungeons & Dragons Anti-Telephone" than I did any where else in this thread.

but then Fiery Diamond said

The racetrack analogy is spot on. Explain how it isn't.

Ok, this ones a little easier. The racetrack analogy goes like this (reprinted in a poor attempt to make this slightly readable)

If I have a circular racetrack that is 1.1 light-seconds long, and observe that the finish line is right there by where the starting line is, and so turn around when the starter pistol goes off and cross the finish line in a second, I didn't really travel faster than the speed of light - I just took advantage of a shorter route.

Effectively, the Astral Plane is the shorter route to everywhere.

It needs some adjustment. To fit it into the topic, you have to assume that ALL OF THE SPACE INSIDE THE LOOP MADE BY THE RACE TRACK as well as the line that segments the Finish and Starting Lines are divided by the Astral Plane.

I can't see it fitting any other way, or else you're suggesting that the destination is spatially next to the source, which would mean that light wouldn't travel on your race track (it would take the same path as the guy who turns around and walks back over the start/finish line). Since 3d space doesn't cross the finish line, we can say that the start and finish are 1.1 light seconds apart. If not, then the source and destination are only a foot step away and the whole rest of the track can be ignored. Important thing isn't how fast your moving, or what route you take. The important thing is that the start and the finish are spatialy 1.1 light seconds apart (in this analogy) within the context of the material plane, and you went from one to the other in less than 1.1 seconds.

The start and finish aren't close together physically in the material plane. An Astral Plane shortcut doesn't speed up the propagation of the very rules of the universe. As Dr. Hinson explained, it's not a trick of the light. If a permanent portal was open, and some one could shine light from the source onto the destination 1.1 light seconds away in under 1.1 seconds, that would only break down causality AND link those spots spatially.

Looking at Fiery_Diamonds version of the analogy, it's interesting that he makes all of the corrections needed to relate the analogy to a one way trip. The issue is the same though. If you get from A to B (in your analogy) by "... we cross the other dimension from A to B, we arrive faster before light along the track does." then you're just describing the space-fold scenario that Dr. Hinson addresses. There is a frame of reference where you arrive at B before you leave A, and because "now" depends on your frame of reference, and ALL frames of reference are equal, you DO arrive before you leave.


you don't change the fact that you are connecting two events at distant points (your departure and your arrival) which in another frame of reference occur in the opposite order. (In the other frame of reference, you aren't just bending space, you're bending space-time such that you travel backwards in time.)

Now, onto...

TL;DR: The OP is arguing that an event hasn't occurred from your frame of reference until you've had the chance to see it happen. This is empirically false (see: astronomy and cosmology).

That's ... not really what I was "arguing" at all. I was trying to understand Relativity of Simultaniety, not the collapse of Quantum wave functions. However, like you suggested I went back and looked at... well not astronomy... or cosmology. I looked at physics instead, and hopefully you'll agree that the second look at physics created something more relevant to the topic. In the explanation from Dr. Hinson, the CORRECT interpretation of Special Relativity agree's with the results of the "Dungeons & Dragons anti-teliphone"

I'm.... not sure what you mean by "empirically false". That seems to be the opposite of what Dr. Hinson suggests. Empirical is
based on, concerned with, or verifiable by observation or experience rather than theory or pure logic In this situation, my understanding of the theory was wrong, but if the event ever did occur, we would observe the same thing, that is, we'd see time travel.

I really only wanted to single out the use of the word Empirical, because that's one of my pet peeves (that and the words Proof, and Logic, and Science. I have too many week spots for people to zing).

Lastly, just for giggles, here's a funny quote I like from Atomic Rockets:

About every six months or so, some science writer stumbles over a reference to "quantum entanglement" or "Bell's Inequality" or "spooky action at a distance", then immediately writes an article or blog post about OMG! Quantum Mechanics can send radio messages faster than light!

Short answer: No, it won't work.

Slightly longer answer: When you send the message, it will technically arrive faster than light. But the message will be in two parts: a scrambled sequence of numbers at the source, and a second scrambled sequence at the destination. The only way to decode the message is with both sequences. So the source has to send the first scrambled sequence to the destination over conventional just-as-fast-as-light radio. Which sort of defeats the purpose.

After receiving both parts of the message at a rate equal to the speed of light, you can find out after the fact that yes indeed there was some faster-than-light communication. Oh, my, wasn't that pointless?

Longest answer:
Back in 1930, several physicists in general and Albert Einstein in particular were quite upset when Quantum Mechanics was invented. Everything about QM was offensive to those who like their physics logical, deterministic, and non-weird. Einstein and co-authors Boris Podolsky and Nathan Rosen wrote a paper in 1935 demonstrating that Quantum Mechanics had to be utterly wrong, or at the very least quite incomplete. The paper set forth a paradox. The two solutions were [a] Quantum Mechanics is wrong or incomplete or [b] there exists bizarre spooky action at a distance which travels faster than light (actually it is instantaneous). Since [b] was obviously impossible, Einstein and his co-authors smugly sat back and waited for Quantum Mechanics to be discarded into the dust-bin of history.

Unfortunately for Einstein et al, in 1964 some clown named Dr. John Stewart Bell wrote a paper showing how to test the paradox (called "Bell's Inequality"), and to the horror of the foes of quantum mechanics it turned out that bizarre spooky action at a distance which travels faster than light actually happens.

This saved quantum mechanics from the EPR paradox, but now all the physicists had to deal with this obnoxious FTL action at a distance. As mentioned above, physicists hate FTL because it destroys causality and thus makes the entire structure of Science collapse into a flaming ruin.

As it turns out: yes, the FTL effect is real but no you can't use it for anything useful. Physicists heaved a sigh of relief (and science fiction writers became quite angry).

It's funny, and notice how it's dealing with Quantum Entanglement, which doesn't have anything to do with FTL VELOCITY as is being understood in this thread. No matter, not even a quantum particle, is traveling the intervening distance. Even in that situation, they basically have to censor effects of QE in order to preserve causality.

Red Fel, I am sorry, but this post is getting long and the conversation is moving on without me. I will respond to your post in a later post of mine.

mathmancer
2014-09-30, 08:51 PM
{{scrubbed}}

Red Fel
2014-09-30, 09:41 PM
Red Fel, I am sorry, but this post is getting long and the conversation is moving on without me. I will respond to your post in a later post of mine.

Well, I must apologize, but I'm about to complicate things further. Consider the Alcubierre drive (http://en.wikipedia.org/wiki/Alcubierre_drive), which subverts the FTL limit by distorting the space around a body through the manipulation of gravitic fields. This is a simplification, but basically, by expanding space behind it and contracting space in front of it, a ship can move forwards - even at seeming FTL speeds relative to outside objects - without actually moving. Do you remember that episode of Futurama, where Cubert Farnsworth suddenly realized that the Planet Express ship is able to move in its impossible manner, not because the ship itself moves, but because its engines move space around it? It's sort of like that, except not.

If we accept that the Alcubierre drive provides us with a scientifically feasible method of subverting the FTL limit, and despite approaching light speed relative to outside observers does not create temporal issues, then it is reasonable to accept that methods of travel that distort space around a body rather than involving the body itself moving may not raise FTL concerns.

If, in turn, we accept that it is possible to move a body relative to other objects, without actually moving the body, by distorting space around it, then we can move on to the next step - the Astral. We can draw an imperfect parallel between movement through the Astral and use of gravitic distortion fields. But where the Alcubierre drive involves creating gravitic distortions in front of and behind the object, teleportation via the Astral involves planar distortions. Both systems involve a body that need not be actually moving. In fact, the Wizard casting Teleport does not move - he is displaced by outside forces. Specifically, he is displaced into the Astral, and then shunted back into the Material at (or close to) his destination. The Alcubierre drive, again simplifying, operates on a similar principle - because we are not accelerating the object, the object itself does not move. We do not need to expend any energy to propel it forward. Instead, gravitic distortions simply cause it to be displaced in space.

And... discuss. :smallamused:

Steel Mirror
2014-09-30, 09:48 PM
And... discuss. :smallamused:From the perspective of how the antitelephone phenomenon works, I don't actually think it matters how the FTL movement/communication happens. It could be straight up breaking relativity by somehow moving at superliminal speeds, it could be teleportation, it could be wormholes, it could be mucking with spacetime like an Alcubierre drive, it could be an ansible/sending spell. All of those allow for faster than light communication, so all of them allow for causality to be violated thanks to how inertial frames of reference work, if you keep insisting on a world where general relativity applies.

All of those methods of breaking the lightspeed limit have their own interesting quirks and are cool to think about in their own right, but the antitelephone concept creeps in if any of them are possible, or if all of them are, equally. I think...

mathmancer
2014-09-30, 11:13 PM
Told ya I'd respond Red Fel! Here I go!


That said, I think you're making an assumption. Let me illustrate a situation, and then I'll get to that assumption.

Now, you opened the thread with a situation in which a person travels faster than light, and therefore appears to arrive at his destination before he left, and therefore actually arrived before he left, and therefore traveled through (an infinitesimally small amount of) time. Fine. You then go on to observe how the same holds true of D&D-style teleportation, which is extradimensional via a universally coterminous plane.

Let's examine that scenario. Ulric the Wizard is in the Deserts of Hotendrai. He casts Teleport to leave that horrible place and return to his home in Kuhlendahmp. One standard action later, Ulric vanishes into the Astral. Ulric reappears in the Material, in (or close to) Kuhlendahmp.
Now, as I understand you, your assumption is that, like FTL, teleportation results in the person being objectively observable at his destination before he leaves his starting point, and therefore that he has in fact arrived before he departed.

Yes, exactly. You understand my words and my intent. I think.


I'm not sure that teleportation supports this, for several reasons: Relativity is based upon motion through space.

Ah. Yes that's the hang up that a lot of people have had so far. I could just point you at some of the other posts I've made since then, but instead I'm simply going to say that Relativity has many far reaching implications. The one that I'm exploiting for the d&d anti-telephone is called Relativity of Simultaniety. No motion is needed, as Dr. Hinson points out.


It does not, to my recollection, presume the existence of instantaneous transit, such as teleportation.

directly? No, but if you look up the EPR paradox, you'll see how the creators of the Theory of Special Relativity were setting out to show that instantaneous transit is impossible.


Applying the one to the other seems a bit tenuous. The passage of time is more complex in a multiplanar cosmology. Note that the Astral was originally written as a slow-time plane, with years passing on the Astral for each day on the Material; it was updated to be a timeless plane, meaning that time does not actually pass while traveling in the Astral. In effect, this turns relativity on its head; ages can pass for Ulric, who will emerge precisely when he departed.

Yes. Look at the second post I made in this thread. I discuss how magic in general, violates the laws of physics. That's the defining feature of magic.


Physics fails in a D&D setting. Try to model an explosion. Or calculate pi. Or determine an object's terminal velocity or the damage it can cause while falling. Physics fails.[/list]

don't mix your science and math! Pi is simply (haha, simple?) finding the ratio between the circumference and the diameter of a circle. As long as circles exist in d&d, and they have a circumference (would it still be a circle if it didn't?) and these d&d circles have diameters (again, how could they not?) then I don't see why we can't divide one by the other. It's just a ratio.

As for the other things, yes, d&d does screw up mechanically. It can sort of model an explosion, and it can sort of determine a terminal velocity, but those values would not match up to a universe like ours. As for damage, there is a lot of discussion on what damage in d&d "is", so we have no way to relate damage to real life.

Case in point, the peasant rail-gun (which would actually be ANOTHER method of creating a d&d anti-telephone by the way). That's just not possible in real life, but the mechanics of d&d allow it. Generally though, every one would agree that that's not Rules As Intended. The rules don't even attempt to model real life physics, and they don't need to. That would make a very boring game! But the rules of the game don't carry over into the narrative in many many ways that allow real life physics to leak in. There aren't, generally, any rules for gravity in d&d, but people still have to have wings or magic to fly.

Another good case: The astral plane! You brought up how it's timeless! However, the mechanics for a fight in the astral plane are the same as they are on the material plane aren't they? There are still turns that are meant to represent 6 seconds of time passing.

And while it's not d&d, d20 Future even tried to introduce rules for time dilation.

Ultimately though, we either just need to agree that the d&d setting either includes relativity, or we don't agree. To keep a MEANINGFUL discussion going, lets just proceed as though relat


As a final point, I'd like to note that all observers do not see the same thing. The classic example is the "lightbulb on a train" problem (http://www.phys.vt.edu/~takeuchi/relativity/notes/section09.html). (I make no guarantees for quality; I grabbed the first example I could find.) You have three parties - one fixed to the ground, one fixed to the train car, and one moving faster than the train car. At a certain point, the one on the train car turns on a light in the train. Each one observes the light reaching the different parts of the train in a different relative frame. That's how relativity works. The light does not move differently based on what each one sees; rather, the idea is that the passage of time (e.g. before and after) is dependent upon the observer; it is not objective.

In other words, the fact that one observer sees Ulric arriving prior to his departure (and I'm still not quite sure how we got to that) does not mean that he actually arrived prior to his departure; rather, it means that he arrived prior to his departure relative to that observer.

... And now I'm giving myself a headache...

Haha, you're actually making the same mistakes I was earlier in the thread. The first mistake you and I both made is that "Observer" is being used in a different way than what we are thinking. The the purposes of special relativity, a reference frame IS an observer.

That's a gross over simplification, so I'll just post the wikipedia definition for "Observer (special relativity)":

In special relativity, an observer is a frame of reference from which a set of objects or events is being measured. Usually this is an inertial reference frame or "inertial observer". Less often an observer may be an arbitrary non-inertial reference frame such as a Rindler frame which may be called an "accelerating observer".

The special relativity usage differs significantly from the ordinary English meaning of "observer". Reference frames are inherently nonlocal constructs, covering all of space and time or a nontrivial part of it; thus it does not make sense to speak of an observer (in the special relativistic sense) having a location. Also, an inertial observer cannot accelerate at a later time, nor can an accelerating observer stop accelerating.

Physicists use the term "observer" as shorthand for a specific reference frame from which a set of objects or events is being measured. Speaking of an observer in special relativity is not specifically hypothesizing an individual person who is experiencing events, but rather it is a particular mathematical context which objects and events are to be evaluated from. The effects of special relativity occur whether or not there is a sentient being within the inertial reference frame to witness them.

Continuing the light bulb on the train scenario (which I was familiar with before), with this new understanding of what they mean by "Observer". You're right, the light does NOT move differently, but you are ALSO right that the passage of time does not remain the same for all observers. But it's fine if the passage of time is different. In that same example of the lightbulb on the train, lets explore what happens to all of those observers.

The observer in the train will see the light from the light bulb bounce off of the front wall of the train car and the back wall of the train car at the same time. This is because, for that observer, those walls are not moving away or towards him.

The observer on the platform will see the rear of the train car coming towards him, while the front of the train car is moving away. To THAT observer, the light will bounce off of the rear of the train car first, because it has less distance to travel, while light will bounce off of the front last, because it has MORE distance to travel.

ANOTHER observer, lets put him on a train moving twice the speed of the first train, will see the light bounce off of the front of the train car first, and the back of the train car last!

But the speed and behavior of light is inviolate. TIME is relative, and what happens first, or what happens last, is dependent on the observer (your frame of reference). But to quote Dr. Hinson again "After I take into account the time it took the light to travel from each event, then I will find the order in which the events truly occurred, and this will determine whether or not there is a true violation of causality in my frame." Now here's the tricky part. If you utilize a method of travel from CATAGORY DS (I'm going to keep using this by the way. See the previous post) then you can't take into account the speed of light. You now have nothing you can use to determine the order in which events truly occur. And that is why, no matter how you did it, CATAGORY DS methods of travel will always result in time travel, destroy causality and "...makes the entire structure of Science collapse into a flaming ruin."

I saw your second post, and I see Steel Mirror already did a fantastic job of answering it though. I can't hope to do a better job.

Cazero
2014-10-01, 06:28 AM
Ok, I think I got it. Simple explanation avoiding complicated physics incoming.
edited for clarity

Let's pick 2 spots in space, A and B. The information going from A to B (and from B to A) takes some time to arrive, handwaved at lightspeed. Wich implies that for any observer, everything is in the past, and the further it is in space, the further it is in the past.

With that in mind, any movement, regardless of speed or distance, sends you in the past. But since you're moving slower than information, time catches up faster than you move, enforcing causality.

In consequence, moving faster than than the speed of information (here, light) from A to B would bring you to a time state of B that you could observe from A during the travel, wich is technically in the past regardless of the method of transportation you used, and not to the time state of B that is "currently happening", because this time state of B actually doesn't exist (yet) when observing from A. If that statement is true, then you are effectively moving in the past, and can use your FTL travel device to return to A even further in the past, and repeat ad nauseam until you arrive whenever you want in the past, allowing to break causality in all kind of manners.

Now, using a logic similar to Zeno's paradox (recursively subdivising the A to B travel in intermediate travels of shorter length), you might argue that you receive information from B while you're travelling, allowing B time state to catch up with you during the travel. Even if that is the case, since teleporting allows you to move from a spot to another without occupying the intermediate positions, it ignores that property by denying B the possibility to catch up, and still send you in the past.

The fact that a B time state "currently happening" can "not exist from A" is counterintuitive, but it doesn't mean it's false.

Mewtarthio
2014-10-01, 08:47 AM
Let's pick 2 spots in space, A and B. The information going from A to B (and from B to A) takes some time to arrive, handwaved at lightspeed. Wich implies that for any observer, everything is in the past, and the further it is in space, the further it is in the past.

Nope. If you observe an event at time t which took place distance d away from you, you can trivially determine when it "actually" took place. If we see an explosion 50 light-years away, we can say that it took place 50 years ago, even if we're only just noticing it now. That's not what relativity's about. With relativity, things take place at different times for different observers, even after they take the light delay into account.

For example, let's go back to the train analogy, only with more significant numbers. Let's say we've got a spaceship that two light-seconds (the distance light covers in two seconds, or ~600,000 km)* long. There's a signaler in the dead center of the ship which sends out a radio message to two sensors on opposite ends of the ship. After receiving the signal, each sensor broadcasts a message containing, among other things, the sensor's precise location relative to, say, the sun.

Now, an observer next to the signaler will pick up both messages at the same time, while an observer next to the rear sensor will first detect the rear sensor's message, then, two seconds later, detect the front sensor's message. However, both observers could factor in the speed of light and agree the messages were sent simultaneously (the center observer would say "Ah, it takes light a second to reach me, so both sensors sent the message one second ago!", while the rear observer would say "Ah, it takes light two seconds to reach me from the front of the ship, so the front sensor sent the message two seconds ago--Exactly when the rear sensor sent its message!").

But what about an observer on Earth? Let's say the ship is heading directly towards Earth at half the speed of light.** Now, if both sensors fire the message at the same time, you'd expect us to hear from the rear sensor two seconds after the front sensor, right? But that's not what happens! Instead, the messages are much closer together; by comparing the speed of light with the locations in the message, we determine that the rear sensor fired off its message ~1.3 seconds before the front sensor!

And what's weirder? Between the observers on Earth and the observers in the spaceship, neither of us are wrong!

*For reference, you could spear all four inner planets on this thing sixteen times over before running out of room.

**The difference between a physicist and a layman, incidentally, is that a physicist actually cares about simultaneity right now, while a layman only prays that, at that size and speed, the ship's got a damn good pilot aboard.

Talesin
2014-10-01, 10:48 AM
I guess the point here is what are you actually trying to achieve?

If you want a campaign where you can have some big reveal it doesn't really matter how the FTL behaves in our universe because it can just behave as you want it to in yours. All you have to do is drop hints and stuff that allows the players to believe that is how it works so your big reveal ends up being a "OMG!" rather than a "oh... so we were travelling back in time too... right.."

I'm not 100% on relativity but:

A simple way to think about it is imagine you're watching a friend painting a picture but you are a large distance away. You watch him start painting, which is the light that is emitted when he started painting hitting your eye, and you could stand where you are and watch him finish the whole picture. It took him 10 hours to paint the picture so it would also take you 10 hours of watching him.

Now let's imagine you travelled back in time to the point where he started and decided you'd move towards your friend to congratulate him on the painting. It took him 10 hours to finish it last time so you set off at a speed that allows you to get there in 10 hours so you'll be there exactly at the point where the picture is finished (this just happens to be lightspeed, but we'll get to that later) However about 5 hours in to your journey you realise that he's finished the painting!

But how could that be?

Well it took the light 10 hours to get to your eye before and half way through your journey it now takes 5 hours. It hasn't taken him 5 hours less to paint the picture, only for the light that is emitted by the painting to reach your eye.

Crap, you didn't get to congratulate your friend at the right time. So you get back in your time machine and go back to the start again.

You realise that because it took him 10 hours to finish the painting and you're 10 'light-hours' away (as it took the light 10 hours to get to you) by watching him start the painting he's actually already finished it just you can't see it.

So you talk to your nearest Teleport-able Wizard and say "Teleport me to my friend". Assuming it gets you there at the very second you left, then you would arrive and be able to congratulate your friend on a job well done.

9 Hours 59 minutes later you think to yourself "oh darn, I forgot my keys" so you ask your Wizard friend to teleport you back to get your keys. Again assuming your arrive at the very second you left your friend you would be able to pick up your keys, turn towards your friends painting and actually watch him finish the painting.

Then a few seconds later you would see yourself arrive there, with the Wizard in tow, and watch yourself congratulate your friend on his picture.

Have you travelled through time? Yes and No. Yes in the sense that you got to watch the picture finished twice and can now see yourself, (which you consider to be in the past because it happened 10 hours ago), congratulating your friend.

No in the sense that if you had stayed in this very spot the picture would have been finished at the same time regardless of whether you went over there or not. So by travelling over to your friend and back time hasn't changed in the slightest.



Basically, relativity is complicated and time is just something you perceive. Whether there is an 'absolute' time or not depends on what theory you agree with.

Also to really mess with your head, it is believed that gravity 'travels' at the speed of light. So if you took the Sun away, using magic since we're on a D&D board, the earth would continue orbiting the space where the sun was for 8 minutes (amount of time it takes light leaving the sun to reach the earth) before continuing off in a straight line.

That's just a theory though, could be complete rubbish

Steel Mirror
2014-10-01, 11:26 AM
Also to really mess with your head, it is believed that gravity 'travels' at the speed of light. So if you took the Sun away, using magic since we're on a D&D board, the earth would continue orbiting the space where the sun was for 8 minutes (amount of time it takes light leaving the sun to reach the earth) before continuing off in a straight line.

That's just a theory though, could be complete rubbishWithout getting into the rest of your post (you should follow some of the links previously provided if you want to read more about how relativity really mucks with "common sense" definitions of simultaneity! EDIT: Or check out Mewtarthio's post, above, which is quite fantastic itself.), gravity has actually been well established to move at the speed of light! Thanks to a friendly celestial body known as PSR 1913+16 (http://en.wikipedia.org/wiki/PSR_B1913+16), physicists have been able to observe and test the predictions of general relativity (http://adsabs.harvard.edu/abs/1989ApJ...345..434T), including the speed of gravity, and it all lined up pretty darn well.

Relativity is pretty well established, it has survived thousands of experiments and numerous theoretical challenges, and nothing has provided any evidence that it doesn't work. Except for at quantum scales or at extremely high energies, but that's a whole new can of worms rolled up in n-dimensions and we're hurting our brains enough already.

Totema
2014-10-01, 11:35 AM
Oh my god, what happened to all these poor catgirls!?

DigoDragon
2014-10-01, 03:34 PM
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. :smallbiggrin:

mathmancer
2014-10-02, 06:47 PM
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.

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 (http://www.askamathematician.com/2009/12/q-howwhy-are-quantum-mechanics-and-relativity-incompatible/) 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
2014-10-03, 04:14 PM
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.