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Cowboy_ninja
2007-09-27, 08:25 PM
ok i have this story arc. it goes like this:

-PC's dying from monster
-Portal opens and unknown figure hurls super weapon and portal close
-PC use weapon and survive
-sessions later they find them selves at a time protal open to their past selves dying from monster
-as they stand their their present selves start to fade into non existance( they cant survive in the past w/o the weapon)
- they hurl the super weapon (still in their posession) to their past selves therby saving themselves


ok what is the origin of that darn weapon? who made it and when? where did it come from? i'm sure i can make up anything about the person that made it but acording to that arc the PC's fond it from them selves? the weapon is in a "time-loop" so to speak...

Pronounceable
2007-09-27, 08:30 PM
As a physics major I feel I'm qualified enough to say: I don't know.

BRC
2007-09-27, 08:33 PM
it could be that at some point between the PC's getting the sword and giving it up, they do somthing that magically upgrades it, and every time it traveled through this loop it got upgraded again,with the upgrades stacking, thus explaining why it's so powerful.

kamikasei
2007-09-27, 08:34 PM
Well, it's a paradox, though I forget the name of the type. A solution could be to have them lose the weapon some time after its first appearance, then find it again, but this time it's the "original" weapon which came into the timeline normally.

Yuki Akuma
2007-09-27, 08:35 PM
This is a classic time paradox that has no real answer.

Due to being a real paradox, and not one of those complicated but quite logical 'paradoxes' (such as the one where a twin ends up older than his sibling after traveling at light speed... which isn't a paradox at all).

Stable time loops simply don't make sense. It's why so many people find time travel stories confusing.

(The proper term is "ontological paradox", but "stable time loop" sounds cooler.)

Ulzgoroth
2007-09-27, 08:41 PM
"where did all you zombies come from?"

Er...Perfectly good paradox, but what's the problem? The weapon was never made. It exists only within the closed loop. It had better be immutable or re-set somehow, since it is infinitely old, but other than that this is the kind of thing you end up with when you play at time travel in a single coherent timeline.

...Do pay attention to that immutable bit. If the PCs change the item somehow during the loop and don't restore it before sending it back, your neat little bundle of paradox explodes messily.

Jack_Simth
2007-09-27, 08:53 PM
A physics major can't help you with this one, as it isn't observed in real life. It's the science fiction writers you need to ask (or those that read a lot of it).

It's your basic temporal paradox - the thing is a closed loop; it has neither a definitive "here it began" nor a definitive "here it ends". From the artifact's perspective, it is infinitely old, and has always existed. It is created from the divine intervention of the DM. If you have a deity in your campaign that has Time as a portfolio, then that one did it.

ocato
2007-09-27, 08:53 PM
Well, it's a paradox, though I forget the name of the type.

I believe the technical term is "Terminator Time-F***"

Yuki Akuma
2007-09-27, 08:54 PM
I believe the technical term is "Terminator Time-F***"

No, "ontological". :smallwink:

Foucault
2007-09-27, 09:05 PM
Yea, I'd say that you have a excellent paradox here than you don't want to mess up by providing any more information. If you want a real pseudo-physical explanation you might consider virtual particles and some of the ramifications of the Heisenberg Uncertainty Principle, the Energy Time Uncertainty. It says that the product of an uncertainty in energy E multiplied by an uncertainty in time t must be less than or equal to Planck's constant over 4pi. The ramifications of this is that for some time t you can borrow some energy E from the quantum background energy, in the real world to create a virtual particle that can be used in a reaction. In your case your borrowing E magical energy for the term t that PC's posses the weapon. The end result is that the item is never created or destroyed, it mere appears when it is needed and disappears when it is no longer needed.

I do however want to add to qualifications on this. I'm only 5 weeks into my Particle Physics course and am yet to take a full Quantum course, I've only taken a Modern Physics course. So this may be completely wrong. The second is that your paradox is fantastic the way it is and I think it would be better without an explanation.

Duraska
2007-09-27, 09:09 PM
A wizard did it.

Dervag
2007-09-27, 09:12 PM
Frankly, having the sword stuck in a closed time loop is as good as it gets. No existing physical model covers time travel, not least because it's convincingly established as impossible in them. We'd have to rewrite all the laws of physics for two-directional causality if anyone ever managed time travel, and the existing theories suggest that we won't have to. This weapon has neither an origin nor a maker nor a 'death' as far as I'm concerned.

So once you've settled the philosophical issues of time travel (parallel time lines versus grandfather paradox versus consistent universe, and so on), there's not much left to say about it.


it could be that at some point between the PC's getting the sword and giving it up, they do somthing that magically upgrades it, and every time it traveled through this loop it got upgraded again,with the upgrades stacking, thus explaining why it's so powerful.In that case, it would have different power levels at the same time.

The sword's effectiveness can't have any net change through one complete cycle, because if I use it now (Sept. 27), run it through a time loop and power it up, and bring it back to Sept. 27, a paradox arises- the sword has both X and X+1 power.

However, the sword can be broken and remade as good as new in every cycle, or powered up and subsequently powered down.


Stable time loops simply don't make sense. It's why so many people find time travel stories confusing.

(The proper term is "ontological paradox", but "stable time loop" sounds cooler.)You're right, but I've never had a problem with them.


Yea, I'd say that you have a excellent paradox here than you don't want to mess up by providing any more information. If you want a real pseudo-physical explanation you might consider virtual particles and some of the ramifications of the Heisenberg Uncertainty Principle, the Energy Time Uncertainty. It says that the product of an uncertainty in energy E multiplied by an uncertainty in time t must be less than or equal to Planck's constant over 4pi. The ramifications of this is that for some time t you can borrow some energy E from the quantum background energy, in the real world to create a virtual particle that can be used in a reaction. In your case your borrowing E magical energy for the term t that PC's posses the weapon. The end result is that the item is never created or destroyed, it mere appears when it is needed and disappears when it is no longer needed.Won't work. First of all, the amount of energy required to kill a villain could only be 'borrowed' over negligible time spans. Second of all, the energy uncertainty is a random factor, not one you can create on demand.

Third of all, energy uncertainty and virtual particles don't even exist in some models of quantum mechanics; it's an artifact of the system that gets explained in different ways by different models.

Really, you're better off just asserting that the sword is in a time loop than mucking around with virtual particles; practically nobody understands how they work and it's too easy to create bad science fiction by pretending that they work in a way that they can't work.

I can't do the math to describe them either; I just know that they are nothing remotely resembling a 'get out of the law of conservation of energy free' card.

BRC
2007-09-27, 09:14 PM
In that case, it would have different power levels at the same time.

The sword's effectiveness can't have any net change through one complete cycle, because if I use it now (Sept. 27), run it through a time loop and power it up, and bring it back to Sept. 27, a paradox arises- the sword has both X and X+1 power.

However, the sword can be broken and remade as good as new in every cycle, or powered up and subsequently powered down.




I know, my idea was based mostly on the players going by the philosophy of not thinking too hard about it, lest their brains exlpode.

Dervag
2007-09-27, 09:16 PM
I know, my idea was based mostly on the players going by the philosophy of not thinking too hard about it, lest their brains exlpode.If they're flexible enough their brains won't explode, but it won't do them any good because there's really only one possible answer you can reach in the 'one past/one future' model of time travel, which is that the sword never came into existence or ceased to exist, but instead occupies a sort of 'standing wave' in the history of the universe.

Icewalker
2007-09-27, 09:20 PM
I'd say...a closed paradox is always a fun addition. Also, I don't think physics is what you are looking for here.

Sounds like a fun paradox to simply baffle the characters without...you know, destroying with universe or whatever.

Bucephalus
2007-09-27, 09:30 PM
sounds a little like the situation in harry potter, though not exactally

Clementx
2007-09-27, 09:37 PM
And your players will think you under CRed the boss fight, and came up with the sword at the last second to save them from a TPK. So this is the DMPC swooping in to save the "incompetent" characters that can't pass History- I mean kill the BBEG - without help.

Bogus

Guildorn Tanaleth
2007-09-27, 09:39 PM
The sword's effectiveness can't have any net change through one complete cycle, because if I use it now (Sept. 27), run it through a time loop and power it up, and bring it back to Sept. 27, a paradox arises- the sword has both X and X+1 power.

But the sword has been through this cycle infinitely many times, and infinity plus one is still infinity.

Yuki Akuma
2007-09-27, 09:44 PM
But the sword has been through this cycle infinitely many times, and infinity plus one is still infinity.

But it's more infinity.

Yes, this actually does make mathematical sense. No, I don't really understand it either.

(Specifically, infinity plus one is not infinity. It's infinity plus one, because infinity isn't a number. And there's more than just one type of infinity, and some types of infinity are bigger than others. Math is weird.)

NecroRebel
2007-09-27, 09:51 PM
When you start getting into true logical paradoxes, it stops being "physics" as such and starts into the realms of "philosophy" and/or "theology." In this case, you almost need to look at seperate temporal viewpoints in order to make sense of the thing.

From an outside observer's point of view, the weapon arguably is created at the instant it emerges from the "time portal." There's functionally no difference between the "portal" creating the device and the device having come from somewhere else; from outside the loop, the device was never observed and was never observable before it emerged from the portal, so it chronologically "begins" at that point.

From the weapon itself's viewpoint, the weapon has always been and will always be, having existed for an infinite number of finite time periods.

Further, it cannot actually change between the beginning and end of a given loop (or more accurately between the end and beginning) because this would force it to have the changed properties in every previous loop and every subsequent loop in which it changed would retroactively affect the earlier loops making it impossible to change the features because the features you were attempting to change would already be how you were trying to change it and so it wouldn't change so it wouldn't have been changed so you'd have to change it so...

And so on and so forth. The simplest way to do things would be to have the device literally impossible to change; have it be completely pure, mirror-like silver (except more reflective than any real metal can possibly be) since it cannot absorb light, have it always cool to the touch since it cannot radiate or absorb heat, have it unbreakable (unless you want to have it repairable, in which case a particular person would have to repair it with particular materials, by which I mean specific bit of material), etc. Basically, it has to end just as it begins.



One big problem with a time loop like this is that it effectively includes a predestination effect. The character(s) must be at the time portal when it opens to the past, which logically means that they're in absolutely no danger during the time they have the weapon. After all, if they die, who throws them the weapon in the past?

If you run this idea, just make sure your players don't realize that... Otherwise, they'll have a good reason to just ignore any monsters that attack them, since they can't actually die or anything nasty like that:smallsigh:



Personally, I choose to avoid time travel in my stories. It just brings up way too many questions and is terribly difficult to actually explain unless you bring in pseudophysics (which if you have magic in your world you're doing anyway, but... That's different. Somehow.:smallconfused: )

Chronos
2007-09-27, 09:56 PM
As it happens, I'm both a physics major and an afficionado of time travel. An object such as the weapon you're describing is referred to as a "djinn" (yes, like the middle-eastern wind spirits, though I'm not certain what the connection is). Usually, a djinn is either a subatomic particle, or a piece of information, since macroscopic objects have problems with durability. If it ever gets a scratch on it, or the edge dulls a little, or a little bit of the paint wears off, or suffers any other sort of damage, no matter how minuscule, it's suffered that damage an infinite number of times, and is therefore destroyed. One way around this is to make the object completely immune to change (hey, there's magic, it's allowed to do that). This is also how subatomic particles can get around this problem. Another solution, though, is to make the object capable of repairing or healing itself. This is how information makes it through such a loop, and could also work through magic. Personally, I would prefer the latter.

I also wouldn't have them fading out in the "future" while they watch the battle... They either survived or they didn't; there's no good way to account for them being "faded". Instead, I would have the superweapon call attention to itself in some conspicuous way while they're watching: It might vibrate in their hands, or make a loud noise. Or if they still don't respond, it might become red-hot, causing the player wielding it to throw it out of his hands (at which point you declare that he threw it through the portal). If they're obstinate enough to not take the hints and still try to keep it, abruptly switch scenes, and replay the last round of the monster combat, tell them that they see a portal open above them with shadowy figures behind it, but the figures do nothing, and the monster finishes them off. End of campaign.

Oh, and Ulzgoroth, "By His Own Bootstraps" was better.

Yuki Akuma
2007-09-27, 09:57 PM
The "what if they die?!" scenario is quite easily solved by simply not letting them see who throws the weapon through the portal. So, they might be the ones who will have done it (time travel grammar is confusing), but it could easily will have been (see?) someone else.

Although, even if they see themselves doing it in the future, it could easily be someone else under the effects of alter self.

Fhaolan
2007-09-27, 10:00 PM
Of course, you can always have whatever the characters do to the weapon be undone by the portal itself.

Weapon has power X after exiting the portal
Characters add power Y
Weapon now has power X + Y
Character throw weapon through portal
Portal absorbs power Y
Weapon has power X after exiting the portal

Or:

Weapon has power X after exiting the portal
Characters consume power X
Weapon now has no power
Character throw weapon through portal
Portal charges weapon with power X
Weapon has power X after exiting the portal

Of course, while this makes some sort of vague sense, it's very unsatisfying to the players who wanted to 'splode casualty. :smallsmile:

Azerian Kelimon
2007-09-27, 10:01 PM
Might I say something? this is not a closed paradox. This is either:

1) A universe breaker. If the sword was just popped outta nowhere, the universe collapses. Period. Which means, you've screwed up royally, and I suggest that you bring a char that has a high enough level to cast a Vengeful Gaze of God cast a Perfect timestop at the Portal, which allows for the apparition of the superweapon.

2) A would be paradox....cept that portal might be used as a gateway tot he past by the PC's. In that case, you break the paradox, the weapon has a definite (if sketchy) beginning, and you end up coolio, assuming you give each PC "clone" the ability of free choice, and NOT the illusion of free choice.

NecroRebel
2007-09-27, 10:02 PM
The "what if they die?!" scenario is quite easily solved by simply not letting them see who throws the weapon through the portal. So, they might be the ones who will have done it (time travel grammar is confusing), but it could easily will have been (see?) someone else.

Although, even if they see themselves doing it in the future, it could easily be someone else under the effects of alter self.

True. And if the portal is only described as having "shadowy figures" behind it, they wouldn't even have to know it was a time loop. Of course, that comes under my advice of "don't let the players know that," so I'm going to claim that I thought of this myself :smalltongue:

Yuki Akuma
2007-09-27, 10:03 PM
In a world with greater creation, I think the universe would be built to handle matter suddenly coming into being.

Heck, the real universe can take it, although, granted, it happens on a much smaller scale. On a scale so small, in fact, that it's not really matter, just this sort of... stuff, that only kind of exists.

But on that scale everything only barely exists anyway.

Azerian Kelimon
2007-09-27, 10:05 PM
If that was an answer to my post, yep....IF THIS WAS A GREATER CREATION. This weapon was made "out of thin air", which means that it wasn't based on the weave. Which means it's non magical, and so is "natural". Which causes a universe breakdown.

Yuki Akuma
2007-09-27, 10:06 PM
The portal could easily be magical.

And the "weave" is a Forgotten Realms thing. Other settings get along fine without it.

Demented
2007-09-27, 10:33 PM
So... ye want to know where the weapon came from, eh? Well, if ye know the secret ta wisdom, ye'll find that yer selution is quite simple.

Ask yon weapon. *wink*


As for its actual origins...
Perhaps the PCs would have created the weapon later on, had they not recieved it through the portal. And these supposed original-selves did so with the intent to create just this sort of self-resolving cycle, in order to ensure that whatever BBEG the PCs are dealing with is assuredly defeated. As for the weapon's eventual degradation... Well, everyone's already speculated on that, but I especially like the idea of the weapon being reforged... It doesn't have to happen that often (if such a relative term could be used here), but every once in a while is good enough.


Though, I'll say right now that I've never been much of a fan of BttF's method of time-deus-ex-machina.
Time: "If you don't do what's needed to maintain causality, I'll... I'll... make you disappear!"

Person: "What? You can't do that! Everything I've done and everything I've changed will still remain! I'll have been the arbiter of change that caused the existance of my own nonexistance! Even if you undo the changes, it will all be as before and I'll inevitably be back here talking to you. This is rediculous! Not to mention that fading is implausib–"

Time: "Shush. Do what I say, wiseass, before you gain the consistency of meringue."

CharPixie
2007-09-27, 10:49 PM
Alternate solution: parallel but time-phased dimensions.

The weapon originally came from another world. The other-yous were not-you; rather, they were yous with similiar choice/environment/situation streams. So, they could end up NOT saving theirselves.

This kind of story gets good if they were fighting something really down-right nasty. Whether you incorporate the "other world" into the equation, or make the superweapon be something creepy is up to you, but I would. An engraving about "born in the blood of PC's family" might work.

Dervag
2007-09-27, 11:11 PM
I'd say...a closed paradox is always a fun addition. Also, I don't think physics is what you are looking for here.

Sounds like a fun paradox to simply baffle the characters without...you know, destroying with universe or whatever.Is there really a paradox? I don't see one.

I'm under the impression that a paradox is a situation where a presumably true statement contradicts itself. "This sentence is a lie." creates a paradox. Travelling back in time and preventing your own origins (such as by disrupting the events that led your parents to meet) creates a paradox in a one past/one future model.

Here, we have a confusing situation, to be sure, but there is no paradox because nothing in the situation makes it impossible for the situation to occur.


But the sword has been through this cycle infinitely many times, and infinity plus one is still infinity.Actually, there is a direct analogy here to 'normal' physics. If an object is moving around and around in a loop in space, and if its properties are stable, it must neither gain nor lose energy on each pass through the loop. Otherwise you get infinitely energetic particles, which cannot exist.

I don't know what an 'infinitely powerful' sword would behave like, but I don't think it would be even remotely safe to lose- it could probably chop you in half just by being looked at.


Further, it cannot actually change between the beginning and end of a given loop (or more accurately between the end and beginning) because this would force it to have the changed properties in every previous loop and every subsequent loop in which it changed would retroactively affect the earlier loops making it impossible to change the features because the features you were attempting to change would already be how you were trying to change it and so it wouldn't change so it wouldn't have been changed so you'd have to change it so...

And so on and so forth. The simplest way to do things would be to have the device literally impossible to change; have it be completely pure, mirror-like silver (except more reflective than any real metal can possibly be) since it cannot absorb light, have it always cool to the touch since it cannot radiate or absorb heat, have it unbreakable (unless you want to have it repairable, in which case a particular person would have to repair it with particular materials, by which I mean specific bit of material), etc. Basically, it has to end just as it begins.The problem is not that extreme. The sword can absorb and reradiate light. It can be broken and repaired, as long as the repair is perfect every time.

The only condition imposed by the time loop is that the sword must be in the same state at the beginning and end of each finite period (from when it emerges from a portal in the past to when it enters a portal in the future). It can do anything imaginable between those points in time, so long as it is restored to its original pristine condition at the end. It can absorb light, be broken and reforged, and absorb heat.

By the way, if it can't absorb heat how is it cool to the touch?


One big problem with a time loop like this is that it effectively includes a predestination effect. The character(s) must be at the time portal when it opens to the past, which logically means that they're in absolutely no danger during the time they have the weapon. After all, if they die, who throws them the weapon in the past?Someone else?


The "what if they die?!" scenario is quite easily solved by simply not letting them see who throws the weapon through the portal. So, they might be the ones who will have done it (time travel grammar is confusing), but it could easily will have been (see?) someone else.

Although, even if they see themselves doing it in the future, it could easily be someone else under the effects of alter self.In which case you can solve the problem by the expedient of having the sword stolen from the heroes and thrown into the portal by some other entity, or stolen and thrown by some sort of 'Time Squad' force such as a deity responsible for making sure time flows smoothly.

Or you could use the actual cartoon Time Squad, if it amuses you to do so.


1) A universe breaker. If the sword was just popped outta nowhere, the universe collapses. Period. Which means, you've screwed up royally, and I suggest that you bring a char that has a high enough level to cast a Vengeful Gaze of God cast a Perfect timestop at the Portal, which allows for the apparition of the superweapon.Is there any reason that this must be true?

If the sword appears in the past, it must have entered the portal in the future. Assuming that the portal doesn't have to be a unique event scheduled to happen at 2:00 p.m. Tuesday, December 23, Year of the Fruitbat, then there are an enormous number of ways for this to happen.

For that matter, even if the PCs contrive to destroy in the future, all that happens is that the loop is broken. Some future Time Squad must then create the sword and send it into the past- and they will succeed, because they already did succeed.

At least, those are the requirements imposed by the one past/one future model of time travel. We know the sword arrived, so it must have been sent, and there is no way for it to not have been sent, though it may not have been sent at a specific time and place.

If we adopt a parallel time track model of time travel, then the PCs can choose not to send the sword back in time with no adverse effects to themselves, although they will be directly responsible for the defeat of their own alter egos in an infinite number of universes if they choose to do so.

Azerian Kelimon
2007-09-27, 11:20 PM
akuma: ALL the worlds have a version of the weave. Magic never comes out of nowhere, except on some novel only worlds. Thus, the wep destroys the universe, or rather unravels it should I say.

Dervag: the wep WAS sent on year of the fruitbat day X hour y minor details z. And you detail what I meant with a Time squad, only I use a sorcerer and that way unparadox it. And the free choice means 2) of my first post. 1) Talks about the times when you have the illusion of free choice only. If we speak of possibly not sending the sword, or sending a note or themselves or whateva, then it's 2).

Roog
2007-09-27, 11:34 PM
-sessions later they find them selves at a time protal open to their past selves dying from monster
[...]
- they hurl the super weapon (still in their posession) to their past selves therby saving themselves

The important question for the GM is:

What will the PCs actually do when they see the portal?

I would think that a good number of PC groups, if they saw a portal to the past, would think of the possibilities of what they could achieve if they went through, jump through, kill the monster with the sword, and proceed to try to make history go their way.

Citizen Joe
2007-09-28, 12:27 AM
ok what is the origin of that darn weapon? who made it and when? where did it come from? i'm sure i can make up anything about the person that made it but acording to that arc the PC's fond it from them selves? the weapon is in a "time-loop" so to speak...

The comic strip Natch Evil did a whole time loop scenario a while back. It was confusing as heck, but made sense within its own logic. The author made a mini-strip to explain the paradox and then after all was said and done, he made a temporal flow chart to explain the more complex interactions.

The short answer is that the weapon comes from the paradox itself. If you're looking for a more defined answer, just remember that the paradox occurs within a small subset of the greater universe, and it is easy to extrapolate that a larger 'anti-paradox' has injected the time bubble into the universe.

Azerian Kelimon
2007-09-28, 12:47 AM
That makes no sense. Antiparadoxes can't exist, for a simple reason: a true, closed paradox, breaks universes (and possibly multiverses, but not magnaverses), or it isn't closed.

Dervag
2007-09-28, 01:27 AM
akuma: ALL the worlds have a version of the weave. Magic never comes out of nowhere, except on some novel only worlds. Thus, the wep destroys the universe, or rather unravels it should I say.You're saying this without knowing the details of the original poster's setting. It doesn't have to be true of all D&D universes, or of any particular D&D universe. If I want to say that magic in my campaign can make matter appear from nowhere, or assemble it from random atoms scattered throughout the universe, fine and dandy.

The idea that creating a time travel paradox unravels the universe is a popular one, but it isn't one that has to be true. It is just as reasonable to say that time travel paradoxes are impossible- that if the sword arrived in the past at time T it must have been sent at some time in the future, although we can't be sure when. If the PCs don't send it back to time T on the day the DM planned, fine. It gets sent later. Maybe a thousand years later. Maybe a million years later. Maybe an identical copy of the sword gets sent back, and not the 'real thing' the PCs are carrying. Who knows?

This approach has one advantage over the approach of saying that the universe unravels because of a paradox. That advantage is consistency. It automatically makes sure that we don't have effects happening without a cause. It lets us deduce that because an effect happened, the cause must have happened. In short, it lets us apply the idea of causation in some form, which is a really valuable thing.

Otherwise, we're just left with the unproved assertion that if anybody causes a paradox the universe falls apart.


Dervag: the wep WAS sent on year of the fruitbat day X hour y minor details z.Well then, there's no problem and no paradox, right?


And you detail what I meant with a Time squad, only I use a sorcerer and that way unparadox it.Well, anything that makes a duplicate sword and sends it back in time, or seizes the sword and sends it back in time, will do. It doesn't have to be a sorceror, but it certainly can be.


And the free choice means 2) of my first post. 1) Talks about the times when you have the illusion of free choice only. If we speak of possibly not sending the sword, or sending a note or themselves or whateva, then it's 2).What I'm saying is that you can fit the PCs' free will into a time travel setting, because you can set up the universe outside the PC's actions so that any time travel paradoxes are dealt with.

The great thing about time travel is that you have an almost unlimited amount of time to prepare to fix a mistake.


That makes no sense. Antiparadoxes can't exist, for a simple reason: a true, closed paradox, breaks universes (and possibly multiverses, but not magnaverses), or it isn't closed.Why do you say that?

Rockphed
2007-09-28, 02:06 AM
Remember, things that travel through time need not only go backward. This sword could be from the past.

lesserarchangel
2007-09-28, 02:09 AM
The paradox isn't the weapon's existence, or its use: it is in a closed-loop, so there is no end and no beginning.

Now, because of annoying little things like entropy and the geometry of spacetime, a closed-loop isn't possible on large scales in our universe. Similar things do show up when you have to sum over all the possibilities of the vacuum fluctuations in particle physics, though (Feynmann diagrams work through the math here).

This is where the paradox comes in: such an object cannot exist, and yet you are seeing it. What gives?

There are three options here, which have been mentioned in various forms above:

DM fiat - do what you want to happen for the plot. Copy universes, causal paradoxes, 'Back to the Future' style foreshadowing all fall into this category.
Allow a large-scale closed loop: the object is in the closed-loop, and from its perspective always has been. It is invulnerable and nothing can stop it from going through the portal to complete the cycle.
The loop isn't closed, but player choice somehow conspires to ensure the weapon appears through the portal at the end.


The second and third apparently violate free choice, but they maintain the illusion of it. Example of the third: someone already mentioned 'By His Own Bootstraps', by Heinlein. The protagonist, by means of a convoluted web of time-gate travel, moves himself thirty thousand years into the future, where humanity has decayed and he can rule the world. At one point, he steals a notebook containing a dictionary of the current language from a version of himself that has already lived in the future for ten subjective years. He goes back in time ten years, uses the notebook to teach himself the language, and prospers. But the notebook wears out and he laboriously copies it over into a blank version, which he doesn't need to use that much. The copy is the original: it is what goes back in time. There is only one notebook and it only lasted a few subjective years.

Now, for your purposes: Heinlein had his character have the appearance of free choice right up until the end, when it all came together at once. Of course, if he had not followed the entire sequence, it would never have had/had/going to have happened. As DM, you'll need to guide your players subtly through a similar progression or they'll catch on.

Machete
2007-09-28, 02:25 AM
Throw a curse on the weapon that makes it kill the wielder if he or she is of a certain race (obscure race) in 2 hours after its been wielded if it isn't gotten rid off.

Have them find a sickly wizard member of that race where the portal shows up (blind UMD activation of an ancient portal time thingy).

The wizard found it and decided to dump it in the past "at which point there'd be two copies" but the wizard, because of the butterfly effect and the time that passed joined up with an artificer the second and every time afterwards who reclaims the item's XP instead of dumping it.

So its up to the PCs to throw theirs back through the portal.


HA! Take that, causality! I think?

Dervag
2007-09-28, 02:49 AM
Remember, things that travel through time need not only go backward. This sword could be from the past.I think the premise is that the sword does go backward in time. If the sword is from the past there's no problem and, for that matter, no need for time travel. Characters pick up weapons from the past all the time; for that matter, we do it in real life (albeit without portals that let us teleport the weapons where needed).


The paradox isn't the weapon's existence, or its use: it is in a closed-loop, so there is no end and no beginning.

Now, because of annoying little things like entropy and the geometry of spacetime, a closed-loop isn't possible on large scales in our universe. Similar things do show up when you have to sum over all the possibilities of the vacuum fluctuations in particle physics, though (Feynmann diagrams work through the math here).What breaks down in a closed loop? Is it a subset of the fundamental impossibility of time travel, or something else?


The second and third apparently violate free choice, but they maintain the illusion of it. Example of the third: someone already mentioned 'By His Own Bootstraps', by Heinlein. The protagonist, by means of a convoluted web of time-gate travel, moves himself thirty thousand years into the future, where humanity has decayed and he can rule the world. At one point, he steals a notebook containing a dictionary of the current language from a version of himself that has already lived in the future for ten subjective years.I loved that story.


Now, for your purposes: Heinlein had his character have the appearance of free choice right up until the end, when it all came together at once. Of course, if he had not followed the entire sequence, it would never have had/had/going to have happened. As DM, you'll need to guide your players subtly through a similar progression or they'll catch on.And if worst comes to worst, someone else makes the sword and sends it back. The sword has to arrive in the past, but that doesn't mean it has to be indestructible. It may well end up being destroyed before it is created (just as if I travel back into the year ten million BC I will die before I was born).

kamikasei
2007-09-28, 06:33 AM
But it's more infinity.

Yes, this actually does make mathematical sense. No, I don't really understand it either.

(Specifically, infinity plus one is not infinity. It's infinity plus one, because infinity isn't a number. And there's more than just one type of infinity, and some types of infinity are bigger than others. Math is weird.)

False; infinity plus one is still infinity. There are different sizes of infinity, but they aren't separated by addition.

kjones
2007-09-28, 08:12 AM
As a physics major here, the problem isn't resolving the time paradox. Your plot is based on a few assumptions

1. The players will be losing against the BBEG.
2. The players will use the superweapon against him.
3. The players will then relinquish it at a later point.

Unless you're heavy-duty into railroading, I hope you can see that all three of these things might not happen. A lucky critical or a failed save could take out the BBEG prematurely. Your players might just be too thick to realize that they're supposed to use it; believe me, it happens. Finally, once you've given them this superweapon, why on Earth would they give it up? I know that if you go by Back To The Future time travel, they would disappear or something, but really this is just railroading your players so that they only have one option in each of those circumstances.

If I were a player, I would kind of resent being jerked around like this.

Lapak
2007-09-28, 09:18 AM
Easiest way to deal with this is to break the loop in the middle.
- Weapon arrives through time-portal, and the characters see that it is themselves delivering it
- Weapon is used
- Weapon is stolen or (preferably) destroyed, causing player despair as they will be unable to save themselves. If they do research, it indicates that they will indeed die in the past if they don't somehow save themselves.
- Players set out on quest to find/create said weapon, knowing that it's possible to get it but with an unknown-yet-definite time limit before they find themselves on the other end of the time portal.

EDIT: In terms of railroading, this plot does absolutely necessitate the loss of the weapon partway through. If it is as ultimate a weapon as you indicate, though, it's not unreasonable that any and all opponents aware of it will devote their energies to acquiring it, destroying it, or making it otherwise unavailable.

Or they may even be prompted to give it away voluntarily (handing it off to someone else in great need, perhaps, assuming a heroic party) and the person they give/loan it to may either depart or lose it 'offstage'.

Eldritch_Ent
2007-09-28, 09:26 AM
I'd go with differing timelines here. This whole nonsense probably started when some epic wizard who has a fetish for messing with the time stream had a close call with death, and decided to give himself a boost by sending a weapon back in time to help his "party" during their time of need, and the sword has hopped from one alternate timeline to the next, each time to the party that had previously possessd it throwing it to themselves.

But that's just how I'd see it. I honestly recommend steering clear of any and all time travel. :smalleek:

Telonius
2007-09-28, 09:43 AM
Your situation is what happens when the god of Time misplaces a weapon.

Runolfr
2007-09-28, 10:41 AM
ok i have this story arc. it goes like this:

-PC's dying from monster
-Portal opens and unknown figure hurls super weapon and portal close
-PC use weapon and survive
-sessions later they find them selves at a time protal open to their past selves dying from monster
-as they stand their their present selves start to fade into non existance( they cant survive in the past w/o the weapon)
- they hurl the super weapon (still in their posession) to their past selves therby saving themselves


ok what is the origin of that darn weapon? who made it and when? where did it come from? i'm sure i can make up anything about the person that made it but acording to that arc the PC's fond it from them selves? the weapon is in a "time-loop" so to speak...

Past super-weapon came from the future PCs

Future PCs need to get the super-weapon from somewhere else.

Perhaps the weapon had charges or some other limit on its use, which expires between Incident 1 and Incident 2, so the PCs lose its use somewhere in between.

Later, Future PCs come across the super-weapon again from another source; when Future PCs see the portal opening, they throw the super-weapon through it.

Otherwise, the existence of the super-weapon is a paradox, but in a fantasy world its existence might be explainable through the intervention of a deity with power over Time.

NerfTW
2007-09-28, 11:16 AM
CAn't they find the sword in the room with the portal, and throw that through, while keeping thier original blade? That way, the sword's timeline stays consistent, just jumping into the past for a bit.

Fax Celestis
2007-09-28, 11:21 AM
Yea, I'd say that you have a excellent paradox here than you don't want to mess up by providing any more information. If you want a real pseudo-physical explanation you might consider virtual particles and some of the ramifications of the Heisenberg Uncertainty Principle, the Energy Time Uncertainty. It says that the product of an uncertainty in energy E multiplied by an uncertainty in time t must be less than or equal to Planck's constant over 4pi. The ramifications of this is that for some time t you can borrow some energy E from the quantum background energy, in the real world to create a virtual particle that can be used in a reaction. In your case your borrowing E magical energy for the term t that PC's posses the weapon. The end result is that the item is never created or destroyed, it mere appears when it is needed and disappears when it is no longer needed.

A wizard did it.

It's like there's an echo in here.

lesserarchangel
2007-09-28, 12:34 PM
What breaks down in a closed loop? Is it a subset of the fundamental impossibility of time travel, or something else?

Two things break: entropy and the geometry of spacetime

Spacetime geometry (Minowski space with Einstein-de Sitter expansion, for those up on the Jargon) says that you can't send information to a point that is outside your forward light-cone (the region in spacetime that can be reached traveling less than the speed of light). There goes FTL and time travel, and any possibility for a large closed loop. Closed loops less than Heisenberg Uncertainty occur spontaneously - pairs of particles and anti-particles jumping in and out of vacuum can be thought of as closed loops - but are completely random, and contain no information. By adding a time portal, we've already broken this part: the portal is a drastic change in the geometry of spacetime (much like a wormhole). We've altered the most basic nature of the universe. That's what magic is for.

Entropy is the real problem: statistical mechanics states that any complex system will eventually come to the state with highest possible entropy, given sufficient time to overcome all the barriers to changing states. A weapon in a closed loop has experienced infinite time, but has not changed state (because it has to be in the same state when you drop it through the portal as when you picked it up on the other side). This gives it probability zero of happening. Of course, DnD likes to violate the laws of thermodynamics too.

I think the best option for a DM is to be flexible here. If you can carefully direct the players through this without obvious railroading, either by making the object indestructible and arranging the drop, or by doing a Heinlein, then I think that it is a pretty cool translation of one of the classic tricks of time travel. But don't force your players into it. You can always have one or two of the tricks above to use. That said: I lean towards their losing the weapon and having to replace it. Presumably, it would be rather overpowered at the beginning otherwise.

dungeon_munky
2007-09-28, 12:46 PM
Well, it seems to me that the physics behind this is in the form of a god from a machine. Or, as the Romans would have it, Deus ex Machina.

The sword was created by the same magics that created the portal. It is tied to the portal and its scope is no farther than the portal's; it came into existance the first time the portal opened, and left when the portal closed for the last time. Such is the nature of magics, and of mages, and of gods.

Azerian Kelimon
2007-09-28, 12:47 PM
Or, make sure they do something different, like come to the rescue of their younger selves. That'll break the loop, and allow for new things to be done. Or, if they choose to throw the wep, make sure that, much later on, they learn that the wep they got wasn't the one they threw, but rather another one created by an epic level wiz.

Dervag
2007-09-28, 05:19 PM
Spacetime geometry (Minowski space with Einstein-de Sitter expansion, for those up on the Jargon) says that you can't send information to a point that is outside your forward light-cone (the region in spacetime that can be reached traveling less than the speed of light). There goes FTL and time travel, and any possibility for a large closed loop. Closed loops less than Heisenberg Uncertainty occur spontaneously - pairs of particles and anti-particles jumping in and out of vacuum can be thought of as closed loops - but are completely random, and contain no information. By adding a time portal, we've already broken this part: the portal is a drastic change in the geometry of spacetime (much like a wormhole). We've altered the most basic nature of the universe. That's what magic is for.I have long suspected that the D&D multiverse is not relativistic. This is demonstrated by the fact that we know it is possible to travel faster than light in the setting (teleportation).

Maybe if you performed the Michaelson-Morley experiment on the Prime Material Plane you'd confirm the existence of the luminiferous ether...

We tend to assume that any universe that follows any laws of physics must necessarily follow modern style laws of physics.


Entropy is the real problem: statistical mechanics states that any complex system will eventually come to the state with highest possible entropy, given sufficient time to overcome all the barriers to changing states. A weapon in a closed loop has experienced infinite time, but has not changed state (because it has to be in the same state when you drop it through the portal as when you picked it up on the other side). This gives it probability zero of happening. Of course, DnD likes to violate the laws of thermodynamics too.Isn't that statement about maximum possible entropy only true for a closed system? In systems being acted on by an outside force it doesn't always hold. For instance, a room full of rocks that are distributed randomly in three dimensions (some near the ceiling, some near the floor, in all quarters of the room) has greater entropy than an identical room full of an equal number of rocks that are all on the floor.

But if you introduce rocks to a room on the Earth's surface, no matter how long you wait, gravity will keep the rocks firmly stuck to the floor.

In the case of the sword, the sword must 'repeatedly' experience such events as repairs and sharpening in each cycle. If so, it is not a closed system. And so it can, theoretically, leave the loop in the same condition it entered.


Or, make sure they do something different, like come to the rescue of their younger selves. That'll break the loop, and allow for new things to be done.That's fine, but it breaks the "one past one future" assumption. Which is all right, but you should know you're doing it. If the heroes fight the bad guy, then travel back in time and fight the bad guy again, despite the fact that they don't remember being aided by time travelers the first time they fought the bad guy, there exists more than one valid description of the battle between the PCs and the bad guy.

The only way I know to reconcile this is to use a 'parallel universe' construction of time travel. In this model, whenever you travel into the past you create two parallel universes, one in which you arrive and one in which you did not.

In this case, the PCs were born and raised to high level in the universe where they did not show up from out of the future to fight the bad guy. Then they traveled back in time to fight the bad guy, and arrived in a parallel universe that they then altered by their own actions. They disappear from their original universe, and the parallel universe spawned by their time travel now contains two copies of them.


Or, if they choose to throw the wep, make sure that, much later on, they learn that the wep they got wasn't the one they threw, but rather another one created by an epic level wiz.Same thing. This can work great, but only in the parallel-universe setting. Since the heroes don't remember two swords coming out of the portal, the sword they threw into the portal must have gone somewhere else outside the universe they live in.

NecroRebel
2007-09-28, 05:27 PM
Or, make sure they do something different, like come to the rescue of their younger selves. That'll break the loop, and allow for new things to be done. Or, if they choose to throw the wep, make sure that, much later on, they learn that the wep they got wasn't the one they threw, but rather another one created by an epic level wiz.

The problem with this is that you have instant paradox. The original scenario proposed has no paradoxes involved; nothing is selfcontradictory there (even if it does break several accepted realworld laws of physics). If you have something different happen, though, you suddenly have a situation where Alpha Group (the group the players are playing) has a given past, which Beta Group (the group of "PCs" that the players are saving) doesn't experience. Since Beta Group is accepted to be Alpha Group's past, if Beta Group doesn't experience the same past as Alpha Group then Alpha Group never comes into existence (Beta Group instead growing into Gamma Group), which means that Beta Group wasn't saved by Alpha Group (and my not be saved by Gamma Group either since the opportunity may not present itself to Gamma) and so either Beta dies or Alpha does come into existence so Alpha doesn't exist so Alpha does... Etc., etc., etc.

This is just a lesser (and less obvious) form of the classic Grandfather Paradox: "What happens if you go back in time and kill your grandfather before he meets your grandmother?" By performing the given action, you stop yourself from performing the action, which allows you to perform the action, repeat ad naseum.

Granted, your scenario could actually work with liberal application of Programmed Amnesia or other memory-altering devices. If no one actually knows that things didn't happen the way they seem to, then no one is the wiser. Alpha Group (or some other high-level entity) could simply alter Beta Group's memories so that their circumstances appear identical to the ones that spawned Alpha, thus spawning Alpha and allowing an open time loop.

The solution you present also functions with a divergent-timelines model; if a paradox would be spawned, a seperate history is written instead. This is probably the simplest way of solving time-error issues, which is why it seems to be the most prevalent in fiction.



Also... I find it kinda amusing how some people seem to believe in MAGIC and still think this makes no sense :smalltongue:

lesserarchangel
2007-09-28, 05:28 PM
It all comes down to how the DM wants it, but DnD universe rules aren't normal rules, of course.

Re. entropy: that applies only to a closed loop. By breaking and repairing the weapon, we've broken the loop.

goat
2007-09-28, 05:37 PM
Well, assuming some sort of N-dimensional multiverse, the above fits perfectly.

Perhaps a trans-universal god of some sort (this is D&D after all) saw the PCs in trouble and decided, for whatever reason, to help. He calls upon the "same" PCs in an alternate universe where they've achieved significantly more power, and invites them to help "themselves" in another universe by donating them a special weapon they've acquired. Once this has occurred, said god chooses to restrict the use of said weapon by encouraging it to be spread across the effectively infinite set of universes where the PCs are in a life threatening situation.

He thus restricts closed-loop paradoxes by allowing each group to only affect ANOTHER group's past, and yet allows the proliferation of these mortals he's taken some sort of liking to. The weapon has a source, the group isn't affecting its own past. Win.

Citizen Joe
2007-09-28, 06:49 PM
The weapon could have been expended when used by the younger versions, but the original could be gathered by the group. What is worse, the group could send back a request further back to a smith to make the item.

The trick is to model it like two strings. One string is the weapon, the other string is the party. They both loop back but continue and only intersect a little bit.

Dervag
2007-09-28, 07:15 PM
The solution you present also functions with a divergent-timelines model; if a paradox would be spawned, a seperate history is written instead. This is probably the simplest way of solving time-error issues, which is why it seems to be the most prevalent in fiction.Exactly! That's what I said, too!


Also... I find it kinda amusing how some people seem to believe in MAGIC and still think this makes no sense :smalltongue:Magic doesn't normally violate the laws of common sense or of logic. Causes still normally precede effects in a magical setting, and magical effects generally follow some sort of common-sense rule even if they don't obey the laws of physics in their proper form.

Time travel, on the other hand, undermines many people's sense of logic and causation, making it far stranger and more fantastic than mere magic.


It all comes down to how the DM wants it, but DnD universe rules aren't normal rules, of course.The catch is that the DM should apply his rules consistently.

If time travel creates parallel time tracks, then you can't create a paradox because you can't screw up the causal past of your own history; you can only screw up someone else's history.

But the catch is that once you've travelled into the past, you can't go home because of the way parallel universes work. It would require some other kind of immensely powerful magic to send someone back to their own timeline and the history they remember living in.

If time travel does not create parallel tracks and there is only one past and one future, then there can be no paradoxes, but only because history must proceed in such a way as to resolve all the paradoxes. So the heroes (or someone else) must send a sword into the past to defeat the villain. It doesn't have to be the same sword, but it has to happen, because it already happened. The fact that the sword arrived is already determined in the causal past of the universe; so the sword had to be sent at some point.

In which case you can't choose to prevent the sword from being sent back, though you can choose to keep it for ten years or break it in half or whatever. Sooner or later, your decision will be undone, and the sword (or a suitable replica thereof) will be sent back in time to defeat the villain.


Re. entropy: that applies only to a closed loop. By breaking and repairing the weapon, we've broken the loop.Well, my point was that even if I don't actually break the weapon I break the loop of endless decay by interacting with the weapon at all. It only has to decay into nothing if the weapon is a closed system that doesn't interact with its surroundings.


He thus restricts closed-loop paradoxes by allowing each group to only affect ANOTHER group's past, and yet allows the proliferation of these mortals he's taken some sort of liking to. The weapon has a source, the group isn't affecting its own past. Win.In this case, the sword occupies a spiral in time rather than a loop. It returns to its starting point in another universe, so it never becomes itself or violates entropy rules. It still violates General Relativity, but any universe where time travel is possible is perforce at least somewhat nonrelativistic.

Galdor Miriel
2007-09-28, 07:58 PM
Finally, I can unburden my soul. It was five years ago tomorrow afternoon after my evening meal (strangely I remember I will eat fish) that I was thrust through a strange portal by a large glowing silver hand, disembodied and mysteriously all powerful yet not too clean. Since that time tomorrow I have been the pawn of some all mighty chess game played out on the board of modern day existence in Canada, knowing everything that would happen in the world, yet able to do nothing to halt it for fear of disappearing in a cloud of disbelieving skeptics. Am I really here now, five years ago or tomorrow? My soul cries out in torment.

It all started tomorrow, and so tomorrow I will be able to answer your question in September 2002, long before I knew of the existence of Rich Burlew, or even this perplexing question. Being somewhat feeble in intellect, and forgetful of manner, I am unsure whether I will remember to answer your question tonight when the loop loops the loop once more around the loop and this point in time beckons like a knowledgeable woman to the uneducated teen....Or am I already doing so for the infinititith time?


AAAAAHHH to much. I will simply drool, and so contribute in 12 monkeys style, to the human train wrecks ruined by the unknowable, destroyed by the unthinkable and left hanging wondering what next, the same as yesterday?

Cowboy_ninja
2007-09-30, 11:32 PM
As a physics major here, the problem isn't resolving the time paradox. Your plot is based on a few assumptions

1. The players will be losing against the BBEG.
2. The players will use the superweapon against him.
3. The players will then relinquish it at a later point.

Unless you're heavy-duty into railroading, I hope you can see that all three of these things might not happen. A lucky critical or a failed save could take out the BBEG prematurely. Your players might just be too thick to realize that they're supposed to use it; believe me, it happens. Finally, once you've given them this superweapon, why on Earth would they give it up? I know that if you go by Back To The Future time travel, they would disappear or something, but really this is just railroading your players so that they only have one option in each of those circumstances.

If I were a player, I would kind of resent being jerked around like this.


1) i create my own monsters because my group practically has the monster manuals memorized. so they wont know what hit them and why wouldnt they use it?
2) why would they get rid of it? thats where the fadeing comes in. if they dont relinquish it they dont live through the encounter and die that simple. i really hope they are not that stuborn that they would rather die and end the campaign than relinquish the weapon.

i'll reply more but im not done reading all the posts!:smallbiggrin:

Cowboy_ninja
2007-09-30, 11:50 PM
Easiest way to deal with this is to break the loop in the middle.
- Weapon arrives through time-portal, and the characters see that it is themselves delivering it
- Weapon is used
- Weapon is stolen or (preferably) destroyed, causing player despair as they will be unable to save themselves. If they do research, it indicates that they will indeed die in the past if they don't somehow save themselves.
- Players set out on quest to find/create said weapon, knowing that it's possible to get it but with an unknown-yet-definite time limit before they find themselves on the other end of the time portal.

EDIT: In terms of railroading, this plot does absolutely necessitate the loss of the weapon partway through. If it is as ultimate a weapon as you indicate, though, it's not unreasonable that any and all opponents aware of it will devote their energies to acquiring it, destroying it, or making it otherwise unavailable.

Or they may even be prompted to give it away voluntarily (handing it off to someone else in great need, perhaps, assuming a heroic party) and the person they give/loan it to may either depart or lose it 'offstage'.

after reading most of the posts this is what im thinking. breaking the loop. perhaps the sword's timeline can go like this.

1) creation
2) sent to past
3) a few weeks or so where 2 swords exist
4) sword continues to live out the rest of its life

what do you think of that? to pull it off i kind of figured they couldnt know that it was they themselves that send the sword back. when they figure that it was them that sent it back that is part of the climax. maybe i wont make the sword all powerful but enough to tip the scales in their favor . i think i would also have to strip them of most of their significant gear so that they cant send a different item to the past to save them...

anything im not thinking of?

EDIT: nerfTW made me think a bit more. the PC's cant throw the blade they have in the time portal. that creates a paradox. they need to find the other blade the one that hasn't gone through time yet... then again so what if they do create a paradox? as long as either sword is gone right?

Edit 2: also i think it would be best if they did not know they got a sword from the future. whats another word for "time portal" ? :smallwink:

Dausuul
2007-10-01, 12:57 AM
Here's a possibility.

There is an God of Time, who can send weapons of power to those he favors in the material plane. The catch, of course, is that these weapons are created as part of a closed time loop; at a certain place and time, the weapon must be sent back in time to the point where it first appeared. If this is not done, the time loop unravels and reality is returned to where it would have been if the time-god had never intervened in the first place.

Citizen Joe
2007-10-01, 06:30 AM
Party 0 travels along and finds a weapon of power (that also has time affecting side effects). Using the weapon the first time flings the powerful protector back in time and then opens a time window where Party 0 can see themselves (Party 1) getting attacked by the protector that was sent back. Party 0 sends back the weapon to Party 1. Party 1 uses weapon, depleting it in the process, in order to survive. Depleted weapon travels with Party 1 until the point where they find the original (non-depleted) version and the protector. Party one sends back the non-depleted weapon and then proceeds with the depleted one. Presumably, they can get the thing recharged. Of course, recharging it will tend to create time loops.