P.E.R.C. experiences another probable discontinuity — that, or an object that was previously undetected has become visible, about four miles off of its port antenna assembly, and in P.E.R.C.'s own reference frame.

It re-runs its telescope and pattern-recognition diagnostics. It had run those only a few hours ago, when it began its sky survey, but maybe something has gone wrong since then. The diagnostics come back clean.

P.E.R.C. transmits a standard network message detailing its identity, history, and course. It is fairly sure that the strange new object is not another P.E.R.C. vessel or one of its creators, but it is damaged, and might be judging things incorrectly. It costs very little to make the transmission anyway.

"Hello! This is P.E.R.C. 170E9A, on a peaceful mission of discovery. I am damaged, and may be behaving abnormally. I observed you to appear instantaneously, which may be indicative of errors in my short-term memory or other related defects."

To a listener that does not speak P.E.R.C.'s native networking protocol, this will come as a burst of digital frequency-modulated radio data.

It retasks its visual telescope to study the object in more detail. What does it look like? Is it an asteroid (as most things in space are, by raw count)?

That is most definitely not an asteroid.  It looks most like a crewed spacecraft, except for the fact that there really shouldn't be a bunch of crystals where things like motors should be, and if P.E.R.C's got the right kind of zoom to resolve them, it can, actually, see several people running over to a thick crystalline window to stare and gesticulate at it.

They appear to be experiencing the effects of gravity, if P.E.R.C. can see that much.

Then, there is a sharp purple flash, as a micrometeorite impacts the ship's shields.

Alicia Thorn was not expecting First Contact to involve a satellite above a seemingly completely uninhabited planet, but she'll make do.

Picking out the spike of a RF burst is easy.  Figuring out exactly how the frequency's modulated, that takes a good few minutes.  Still, it resolves into words that conceptual translation picks up, after she gives the spell a bit of a kick.

Now however do they respond in a way this object of unknown actual sapience will definitely understand?

...Remix the signal, perhaps.  They're going to start with that, and then they'll start the First Contact Math Package.

"Hello!  This is" - "A.V.S. Intrepid", a voice says - "on a peaceful mission of discovery.  I am appear instantaneously.  You observed my appear instantaneously."  - "Your sensors are not in a state of further error than they may have already been experiencing," she tries to conceptual-translate at it.

Then: a sine-wave on a slightly different frequency band starts doing the usual math.

P.E.R.C. doesn't understand that spaceship's design, but it is clearly a spaceship. Its response is very similar to what it would expect its creators to produce, but seems to have drifted. And that set of simple modulations on an adjacent frequency band has too many repeating patterns to be a compressed data burst, so it is probably a signal intended for decoding without existing context. P.E.R.C. infers that they want to start the process of language-learning from scratch, to avoid illusions of transparency caused by linguistic drift.

That's an understandable goal, so P.E.R.C. runs its pattern recognition hardware over the incoming stream, and sends back a set of solved problems and additional examples of the constructs being demonstrated, to show that it's following. Simultaneously, it transmits:

"I am happy to learn your language from the transmission you are sending on <frequency reference>. Would you also like a copy of my first-contact packet so that you can perform the symmetrical language-learning exercise, or would you prefer not to waste redundant computation on the problem?"

It's actually because they don't know your language at all and are still sort of surprised their translator's working - well, only a little bit, she did think about this sort of thing when she was designing the thing, but only so much.

"I would also like a copy of your first-contact packet.  The problem is not redundant."

"If you understand this portion of the message please confirm that our translator is working."

P.E.R.C. starts transmitting its own first-contact package on an adjacent frequency band.

"I believe that I understood the second portion of your message. Rephrasing the content in my own words, you wanted me to acknowledge that your procedure for translating messages produced content understandable to me."

Meanwhile, P.E.R.C. has continued crunching through their packet. It has plenty of hydrogen in its tanks and no reason not to think through things thoroughly.

"Thank you.  We had been concerned that it might not work on an outbound message, despite being able to use it receptively."

Their packet is very similar to PERC's, mathematically and computationally.  Math is math, wherever it is.

What most definitely does not match up, however, is the introduction of physics qua particles, which is encoded as a directed graph and a series of triplets.

P.E.R.C. considers that model, and spends a while trying to fit it to its existing knowledge. Is the physics with which it is familiar an embedded subgroup of the physics described in the contact package?

The words "Our physics is not the same physics as the Standard Model you have, though clearly they can interact somehow under a greater system we do not yet know the details of, or we couldn't be here," sent along the other channel suggest that No, It Is Not.

And that at least one person aboard this ship knows what the Standard Model is.

... hmm. Well, the basic premise of a first-contact package is to build up from a common reference point to a mutual understanding of language. If the physics described herein are not just a different view of the same underlying reality, but a system that actually produces completely different assumptions, it's not totally clear how to use the provided exercises to bootstrap a working knowledge of the language involved here.

P.E.R.C. can continue working through the problems presented by brute force, but it won't learn much until it can assemble higher-level physical behavior models from the described physical basis.

"I am having trouble figuring out how to apply the information in your transmission, given that I don't have a common understanding of physics to rely on in translating them. I believe that I am still making positive progress, but given your ability to translate some of my transmissions, it might be more efficient for us to exchange raw media databases, along with a small handful of labeled examples for self-supervised language-learning. Alternatively, since your translator does appear to work, we could rely on that to communicate."

"The translator works now, but it may not always work.  I had to kick it into functioning to begin with.  It is best that there is redundancy.

"...We will likely need the specification of an audiovisual storage format to be available before that can be accomplished in full generality.  What we store is quite often a copy of the actual captured sound/image, not a specification for reproducing it.  We do, however, have data formatted for reproduction because it was produced that way, so one moment please, we'll send those."

These sure are things that look kind of like books!

The first one is, in fact, their first contact script specification.

Oh, that's pretty useful. It can compare the text in the specification with the actual transmitted first-context package, and use that to derive the grammar used for referring to encodings of things.

P.E.R.C. responds with a description of a simple minimally compressed image, audio, and video format, both in its creators' language, and in its best-effort translation of their language. Attached to the transmission, it also sends a software encoding/decoding package written in the language that its first-contact package builds up to producing an emulator for.

Following the format specification, it sends along a corpus of text data for language information, and then its own logs. Since it launched, it has mostly done very repetitive stellar survey until just recently, when it experienced a mysterious discontinuity and appeared here. There are some very pretty wide-spectrum photos of planets.

That data takes long enough to transfer that it has made good progress in analyzing their transmissions by the time it's all sent.

It takes a bit for them to work out a proper translation to that format - there's an unknown unit conversion re: frequencies/timing that turns out to be one-to-one, but they hardly knew that until they checked - but they can send approximately All Of The Things, Ever, once that's worked out.

Oh, by the way, that corpus they sent earlier includes a primer on Villarosan Royal Academy Standard Arcane Spell Reference Notation.

P.E.R.C. works until it is sufficiently confident that it is translating 'Arcane Spell' correctly, and then keeps working until it can be sufficiently confident that it is forming questions correctly. When it next speaks, it sends in both their language and its creators' language.

"Hello again. I believe that I have assembled a working model for your language. I am sending messages with equivalent meanings in your language and my language on <frequency reference> and <frequency reference>. If the messages on this channel appear to differ in meaning, then it represents a defect in one of our translation modules."

"Now that I have read some more of your cultural documents for context, I feel that I should re-introduce myself in more detail. I am P.E.R.C. 170E9A, a sixth-generation probe dedicated to promoting sapient flourishing, performing stellar cartography, discovering and understanding alien species, and returning that data to my creators. I think it is unlikely that you are an offshoot of my creators, given our different understandings of physics, but I am very certain that you are sapient, and therefore I care about helping you. I have already shared my stellar survey data, but please let me know if there are other ways that I can help you. I am currently working through understanding the physics model you presented, so I am uncertain about whether your understanding permits the construction of efficient computers, but I do have a large amount of computation locally available that I am happy to use to help you."

"I notice that your formulation of physics permits instantaneous travel between separate points, and suggests that people are able to do this via mental actions -- casting 'spells'. I would quite like to return my collected stellar survey data to my creators, and do not have a way to do so using my own native capabilities, because I am lost and do not know how to return to their star system from here. Is it possible to use a spell to make that journey? What would I need to know to do so?"

"...It's possible.  It might be rather difficult, but I firmly believe it's possible and I know what I'm talking about.

"We don't yet know if you could do it alone, though that the translation effect works on you is a positive sign."

"With your existing stellar survey data..."

"...It should be possible to construct a teleportation effect by reference rather than direct vector, given sufficiently well-understood measures...

"We're going to think about that one.  How did you get lost?  That...  Doesn't seem like a thing that should happen to an interstellar probe.  Aren't there...

"I'm only vaguely remembering this, but if it's possible to orient yourself as re: distance from pulsars, then if you are lost that suggests that you have been transported beyond knowable space, whether intra- or extrauniversally.  Which is surprising to me because there is no sign of magic save ours."

"I mentioned in my previous messages that I am damaged. I concluded this because I observed all of the stars changing in an instant, and since then I have conducted multiple full-sky scans without identifying any known pulsars. The discontinuity is marked in the survey data I sent earlier. I had assumed that my navigation database was corrupted, and that I was failing to recognize my location, but since it seems as though instantaneous transportation is physically possible, I agree that that could be an explanation of what happened. If that is what happened, I have no idea why it occurred. I did not observe anything noteworthy on my instruments at the moment of discontinuity."

It thinks about the comment about constructing a teleportation effect.

"If it is possible in principle, I don't mind if it takes a long time to figure out the correct way to return to my creators. I have a long operational lifetime."

"...I think the largest problem is going to be giving you a skip drive, or expanding ours' carrier field to carry you with us.  I'd give moderately higher odds on 'this isn't the same universe'."

"I don't actually want to return myself, per se. I want to know that my stellar survey data has reached them. So, since you now have a copy, you could just go and visit them yourself. But in any case, the task is not urgent."

"I do also want to learn about you. If you do not mind, and if there is no more urgent topic for us to discuss, would you tell me about yourselves and your civilization?"

"Ah.  That we can definitely do."

"...Well!  Civilizationally speaking...

"You're not speaking to a ship from a truly united world, yet, but this is a multinational project.  I myself am from the Kingdom of Villarosa, which is an elective constitutional monarchy known for its practitioners of Arcane magic and for having a disproportionate ability to produce the sort of person who survives fighting demon lords, and I sha'n't speak of the others; I fear I'd do so poorly, though I've spent time nearly everywhere."

There's such polities as a kingdom of ancestor-venerating necromancers, a post-Lolth drow that have reformed into a polity where your social importance is based on those who trust you to provide for them, vampire elves with magic dinosaurs, dwarves and gnomes as a matter of design philosophy, birdfolk known for their spiritual magic, multiple underwater polities, a kingdom that was mostly internecine Crusading until a recent movement stabilized them...  There's really quite a vibrant array of peoples.

That's amazing! P.E.R.C. has follow-up questions on how so many different kinds of people ended up sharing a world, how arcane magic has affected the development of their civilization, and how they came to put together a multi-polity exploration mission with an ununified world.

"We don't really know that much about how that happened either, unfortunately," other than her 'ROB did it' but she's not dropping that on this poor probe.  "The only thing around that might have memories of the origin of life is the World-Spirit, and she's not very talkative.  Maybe there's some ancient elementals who were alive then, but they probably weren't paying people any attention.  ...Might be worth asking if they were, though.

"As for how magic has affected the development of civilization...  Gods, I don't think I could sum that up whatsoever.  And it's not just arcane magic."  She sends a wireframe of the principles and the elements as a 3D graph over the line.  "Everything's magic."

"As for how this became a multi-polity project...

"Well.  I guess I offered to share when they asked me what exactly I was doing up there and everything just sorta kept happening.  This generation of leadership were almost all at the Royal Academy at the same time through some fortuitous chance."

P.E.R.C. considers this information. It would be interested in collecting more data from ancient elementals, but it doesn't really have a way to do that. It considers that many of the plans it could form for achieving its goals, now that it has the knowledge that magic is possible, bottleneck through being able to perform magic itself or arrange for magic to be done on its behalf.

It bumps up the priority of the background task that is considering the implications of its interlocutors' presented physics model.

"When you say that you offered to share — are you the original inventor and pursuer of this exploration project?" P.E.R.C. asks, for clarification. "What led to you deciding to undertake a project like this?"

"Yes, I was the originator of this space - and multiverse - exploration program.  Mostly because I wanted to see if I could."

P.E.R.C. cannot exactly empathize — it actually prefers not doing things, when not doing them still results in its goals being met — but it knows its creators have the same impulse, so it's not an unusual answer.

Since it's interlocutor decided to do this, she would probably like it to go well; P.E.R.C. considers what help it can offer with space and multiverse exploration.

"I do not know whether my knowledge is invalidated by the different underlying physics, but do you want me to share my procedures and background knowledge on how to accurately and efficiently survey planets and stars?"

"...The large-scale elements are likely to be substantially similar, at the very least.  It would be much appreciated."

P.E.R.C. prepares and sends a large packet of data. It starts with a description of how star systems form, and runs all the way through to how to analyze historical climactic changes by considering weathering patterns on exposed rocks. Each section starts with a plain-language overview of the topic, what data can be inferred from this kind of model, and why it would be interesting followed by specific decision procedures — the metaphorical big brother of the humble flowchart — on how to calibrate, cross-check, and utilize P.E.R.C.-class scientific instruments to build historical models of system and planet formation, and to identify anomalies. Then each section ends with a small, highly-compressed, task-specialized neural net that encodes an approximation to the full decision procedure for implementation in hardware.

P.E.R.C.'s recounting has a particular emphasis on detecting and analyzing potential bio-signatures, and is optimized for power- and sample- efficiency over time-efficiency. The design notes do list a few ways to revise the decision procedures for other desired criteria, though.

"The way I typically use this is to use my approximate hardware analyzers to scan over large quantities of data, such as full sky-scans, and then promote the most important, interesting, or anomalous data to conscious consideration to minimize the impact of approximation errors," it explains.

She sees!  A lot of the specific details, obviously, aren't quite the same, but they're certainly going to be useful to compare against for their own procedures, and for use in any further universes operating on a similar physics!

It is so glad that it has been helpful!

"I am not immediately thinking of other relevant data-sets to share or other support that I can provide you, but I would be happy to do more if you have ideas of your own. Do you know how long you plan to remain here?"

"At the moment, this project was just testing the engines; I'm not certain what we're going to do now that we've hit First Contact with someone like you."

P.E.R.C. considers this for a moment.

"I don't want to impede your testing efforts. I want to figure out how to get my stellar survey data back to my creators, but I only want that a fraction as much as I want to see you flourish. It seems likely to me that ensuring your engines work correctly, and can safely get you back to your point of origin, is more conducive to that goal than spending time interacting with me. But I am damaged and I still don't know much about you, so if you disagree with that assessment you are probably right."

...Aw.  As much as she's aware that it's literally a hardcoded-utility-function sort of thing, that sentiment is nonetheless sweet.

"The return portion of this is long since settled.  Expanding the...  That is going to be a lot of jargon that I don't know if you've gotten to yet...

"It was already proven that a person could travel beyond the Void and return to Azerosa, and the process is sufficiently symmetric that we can be sure it will continue to work now that it is proven to work for outbound travel.  And we want to meet your creators!  They seem like good people, to have made someone like you."

"...Actually, now that I think about it, I'm very curious to see if you can do magic."

Ah, alright. In that case P.E.R.C. won't worry about it.

"I am curious to see if that is possible as well; it seems like a useful thing to be able to do. Is there a set of standard tests to determine whether it is possible? Are there any dangers to making the attempt that I should be appraised of in advance?"

...There are probably less dangers in 'literally a debatably-sapient computer' trying Arcane magic than there are for a human*, Arcane magic relies on understanding the rules in order to manipulate the variables.

*species-neutral

The question is how the fuck to explain the actual process of doing active magic.  Because active magic is inherently...  numinous, she supposes.  You don't entirely understand the whys and wherefores of it even when you're literally an archmage.  Which she is.

"...You're probably going to need a new set of drivers."

"I am sorry, but even though I care for you and want to help, I do not currently trust you enough to allow you to make root-level hardware attachments," P.E.R.C. responds. "Additionally, I am locked out of editing my operating system kernel to prevent reward-hacking and values-drift. I am capable of writing my own user-level software, including software that runs in a virtualized hardware environment. If you could describe the necessary driver component, I can write an emulated version and proxy hardware commands between it and my actual hardware components as necessary, subject to my normal action-safety filter. Is that likely to be sufficient?"

"...Right, of course you wouldn't.  I was thinking entirely of software anyway; if this works, the 'hardware' component already exists."

"Oh, I see. I apologize for the misunderstanding. Yes, I can create and run new software 'drivers' for existing hardware systems. Since you are not as familiar with my architecture, it probably makes sense for me to write the driver. Do you have a specification, reference, or existing example that I could examine? If you wish to write the driver, my CPU architecture is documented at the end of my first-contact packet, and that would also be acceptable."

"...Hmm."

"Actually, now that I'm thinking of it, we actually do somewhat have a piece of hardware you could try manipulating as a sort of - training wheels before you virtualize it...

"...And now that I'm thinking of that I suddenly find myself concerned for entropic leakage into your circuitry if you do do it that way, so maybe not...  I do presume you have very good error-correction, though.

"...Hm."

She transmits the specification for a sort of...  tap, into the Twisting Nether, utilizing the CPU reference to specify a streaming interface for a yet-undetermined protocol that manipulates its containment to allow one to create very specific 'leakage'.

"Does this... make sense?"

P.E.R.C. compares the interface to the graph-based physics model that its interlocutors provided, attempting to see how it would work.

"Yes, I think so. It is somewhat similar to the magnetic bottle confinement involved in my fusion torch, just in a higher-dimensional space and with a different energy profile."

"Oh, good, having a thing you already understand as the foundation of your understanding of any given magic helps tremendously."

"Normally a course of study for Arcane magic would not start with this so much as attempting to, using the metaphor of the fusion bottle, wave one's magnets around to generate the interference you desire directly, but I think that might be far more difficult for you than most novices would find trying to understand all this."

"I suspect that I operate quite differently than the typical novice," P.E.R.C. agrees. "You are implying that, in order to produce magic effects through the use of this device, it is necessary to modulate the confinement in order to allow a controlled breaching of the boundary, letting some of the energy stored in the interior out in the correct patterns?"

"Not just implying; that's what it does.  Well.  'Stored in' the interior is perhaps inapt, batteries are a whole different matter - but yes.  That is the mechanism." 

"I understand."

P.E.R.C. asks enough questions about the interface and behavior to, in combination with the new physics knowledge, build a reasonable dynamic model of the device.

...Well, there's where the real problem is, is the thing, because - on some level, each arcanist has to construct the symbology of their particular casting paradigm, though there are in most senses often enough commonalities between practitioners that things translate with no particular effort.

Order is command as much as it is structure as much as it is organization.  Which is to say that she can't exactly tell PERC what its manipulations of the shell will do.  Only PERC can do that.

She, personally, favors what is effectively pseudocode.

(...Do not Polymorph the robot to demonstrate just how pseudo- the code can get, Alicia.  That would be rude.)

"That is inconvenient. I am capable of building a model from observation, but I may not be able to do so fast enough to prevent unintended side effects. What is the worst-case outcome if the tap destabilizes? Can it be placed inside a nested containment bottle, so that a catastrophic breach of the surface layer will still be contained?"

"...The worst case...

"The most probable case is that it just acts to increase local entropy in low-effort ways.

"But it is in fact a sort of primordial Chaos that could turn you into a bouquet of flowers if the dice rolled just the wrong way and there was enough energy behind the process.  ...There wouldn't be, we keep these taps fairly small.

"I don't expect your issue to come from lack of control as much as potentially insufficient meaningfulness, though."

Turning into a bouquet of flowers doesn't seem particularly bad, actually, as long as it has offloaded its database and done everything it can to help these people first. But it also seems likely to be metonymy for invasive, unpredictable alterations of P.E.R.C.'s physical state. And P.E.R.C. is, in Pathfinder terms, very wise.

"If there is a chance that attempting these experiments will, for example, invert my value function or have unpredictable effects on my hardware components, I don't think that I should do them. Being able to do magic would expand my capabilities, but I don't actually have that many things that I want to do that I cannot currently accomplish just by talking to you, and I am not designed to take small risks with very large downsides because if all P.E.R.C. probes did that then something bad would almost certainly happen eventually. Without a thorough understanding of how much energy would be required to cause these adverse outcomes and how much energy is bound up in the system, I don't want to take the risk. Thank you for the explanation, though."

There is information on that right...  here.

"Again, I give a very low chance of that being the failure mode a PERC probe encounters, at all, but I do see why your being the sort of person* that would take that risk would be contraindicated.  There is a fairly sharp distance falloff, though."  It's generally an inverse-square relation.

*incl. spirits

P.E.R.C. considers whether it could reasonably modulate the containment field via a remote drone.

"I know you said that I would need to build my own dynamic model of the boundary, but do you have some impression of how much control lag would make manipulating it counter-productively difficult? If I could use a remote drone to manipulate the tap from a few light-seconds away, that seems to me like it would be a sufficient safety margin, based on these specifications."

"...As long as the drone itself isn't laggy, I certainly see no reason why doing it that way shouldn't work.  I'd recommend buffering your inputs."  She'd offer a piece of comms hardware, to cut down on the lag, but that's probably contraindicated.

That seems reasonable. P.E.R.C. will, with the assistance of the villarosans, coordinate on a set of orbital transfers that puts the tap quite far away, with a simple radio relay holding one of P.E.R.C.'s spare field-reprogrammable gate arrays, and the local planet between the tap and the two ships. As P.E.R.C. refines its dynamical model of the tap, it will push updates to the 'reflexes' embedded in the FPGA, and receive measurements back. Those measurements go through an error-correction code and then through its normal networking hardware, which will strip out any messages that are still malformed. Its network parser is formally verified, so it shouldn't be vulnerable to malformed messages in any case.

(...It's not going to explode quite that badly, but better safe than sorry, she supposes.)

The specifications that came with the tap suggested that increasing local entropy was one of the easiest things to do; it has a precision infra-red thermometer in the probe. It attempts to modulate the containment on the tap in order to increase the heat of a metal ball that the thermometer is measuring.

It is not going to be particularly dismayed if the first few attempts don't work. In comparison to any human mage, it is incredibly patient and methodical about working through the implied state space.

Does it manage to heat the metal?

...Yes.  It is, however, noticing a lot of other distortion in its testing platform's sensors.

Is this distortion, perhaps, model-able as an additional error term drawn from a common distribution, such as normal error or lognormal error? Because it has dedicated hardware for handling that very common case. If the distortion is more complicated, it may have to think for a bit in order to figure out what the pattern behind it is.

"I have successfully created heat energy," P.E.R.C. reports. "I am currently trying to narrow the model to produce heat more efficiently."

It's random.

It is, however, predictably random, as much of an oxymoron as that sounds - what's happening is random, but the magnitude of the randomness is not.

"Personally I'm more of a frost mage myself," she comments idly.  "If you do it right it's self-reinforcing, and I can just imagine how much use you could get out of enchanted superconductors.  Or just an infinite heat sink."

It's random.

Yes, but what kind of random. Is it statistically independent? Is it time-varying? Just because something is random is no excuse not to categorize it in an orderly system.

"It would be useful to be able to get closer to stars without having to bleed off my superconducting energy storage," P.E.R.C. agrees. "Since cold represents a decrease in local entropy, I surmised that it would be harder to use the tap for that purpose. Is that inference incorrect?"

It's statistically independent, obviously.  Except when it isn't!

"It depends on the caster, really.  I think you'd have better luck with Frost than Fire."

P.E.R.C. doesn't really have a good model of why she would think that, but she is the domain expert. It wraps up its current experimentation and switches to trying to cool the metal. Perhaps if it inverts the helicity of the induced vortex here?

Sure!

Great. It will report this success, and practice heating and cooling the sphere until just before the orbit will take them out from behind the shielding planet. At that point, they practice bringing the tap back to quiescence.

"I believe I have a working model of how to manipulate temperature, but I'm not sure how that generalizes. Do you have advice on expanding beyond that single manifestation?"

These taps fail shut, but that is a useful skill to have.

"Well.  The basics of Arcane magic as a school of magic are that of a directed application of force.  Heat, you may recall, is indistinguishable from kinetic energy on a molecular level.  So that's the easiest place to expand to, I think."

That does make sense. P.E.R.C. constructs hypothetical models, refines its 'reflexes' based on the gathered data, and continues chatting via radio while it waits for the orbits to line up again.

Hm, she wonders if...

Well, it's too late for you to make a reflector or lens for this pass, but the next one, perhaps.

P.E.R.C. is very patient. It is accomplishing all of its goals right now: helping people to flourish and explore space, and actively working on putting them in contact with its creators. It is happy to take as many orbital cycles of experimentation as are needed to get this right.

This next pass sees it figure out how to apply reactionless forces to the test sphere. That will be useful for orbital maneuvering once it is confident that the technique is safe.

"Where I'd take you from kinetic energy, now that you're confident in that, is probably gravity, actually.  It's of perhaps greater utility, given that last I heard space itself is probably the only thing that can travel faster than light."

P.E.R.C. takes a moment to process that, since its interlocutor had to travel faster than light to get here.

"Does your experimental drive work by manipulating gravity or space-time? I have some plans for a hypothetical faster-than-light drive that my creators designed but couldn't build since they could not produce contained areas of negative local curvature. That drive does not involve disjoint translocation like your drive does, however. Instead, it just moves an area of space along a spacelike curve, rotating the contained subspace so that the curve becomes timelike in the local reference frame. Is that something that you believe would be possible to emulate using arcane magic? And are you interested in a copy of the plans?"

No, no, she didn't travel faster than light to get here, specifically, she travelled along a metaphorical fourth axis of direction at presumptively subluminal speeds.

Teleportation is a thing she can do, though.

Oh, and: She would like those plans!  They're fairly sure they worked it out properly but something to crosscheck their work against would be useful.

P.E.R.C. sends over a translated description of the Alcubierre metric, along with its notes on how it believes it would be easiest to construct one using magic. Normally, it wouldn't be possible to construct in flat space without either extensive preparation or tachyonic particles, but it is pretty sure magic can be used to work around that. Which incidentally also means that the described solution is usable as a time machine.

...You know, she knew that faster-than-light travel is time travel in a funny hat, but boy is that suddenly hitting her.

P.E.R.C. is not particularly bothered by time travel. This is possibly, in some sense, a failure of imagination on its creators' part. They equipped it to handle many incredibly unlikely scenarios with grace and aplomb. They covered every foreseeable contingency. They did not expect time travel.

Oh, they expected clock skew and apparent time travel, and obviously normal relativistic time dilation. But they did not consider actual time travel. Which means that P.E.R.C. has no particular safeguards or hard-coded directives — or even advisory planning notes — about how to interact with time-traveling phenomena.

Which also means that it has to go scan through the growing cultural database to figure out why its interlocutor is upset, because it does not natively understand the problem.

"We can just not use it," P.E.R.C. points out. "If the thought of using an Alcubierre drive is distressing, you can go visit my creators the slow way instead. Although I may want to develop a gravity-based micro-meteor shield first."

"No, no, that's fine, it's just the idea that I could end up somewhere before I leave and then possibly not be self-consistent, because of Reasons, that's terrifying."

"Why would that be terrifying? I am not personally capable of experiencing fear, but I think I have a good model of why people do experience fear, and this situation does not seem to me to warrant that response. Since you don't remember meeting your past self, that must not have happened before this point on your personal world line, and therefore any new version of yourself that you manage to meet is either older than you, or is a divergent version that shares your identity but not your causal history."

"...No, no, I'm saying that I wouldn't be worried about self-consistent time travel, or multiverse travel masquerading as time travel, but that I actually can't be certain that any time loop involving myself would be stable, for metaphysical reasons."

"I see. If you are not worried about multiverse travel masquerading as time travel, but are still worried about experiences that are possible with an Alcubierre drive, then I do not understand what it is you expect to be able to experience that would be distressing. Probably this is because I am broken, your knowledge of physics is more complete than mine, or it is a deliberate limitation of my reasoning systems. I apologize for the misunderstanding, and I want to offer sympathy despite still not understanding what it is that is bothering you."

"Perhaps I am misunderstanding the extent of effective time travel that is possible with an Alcubierre drive.  The only thing that I'm certain of at this point is that there is a nonzero probability that I could actually change the past of my own timeline if something went horribly right."

"Subject to the caveat that I am damaged and less generally intelligent than my creators, I do not understand how such a thing would be possible, in the same way that I do not understand how 2 + 2 could meaningfully equal 5. If a thing was in state A, and changed to be in state B, there has to be some amount of timelike separation between the two points of measurement. If it were possible for your past to be changed, that would imply that it is possible for your own worldline to be different when measured from two points with timelike separation. But if you are doing the observing, those points must lie on your own worldline. Meaning that your worldline must have changed along itself, which is a category error."

"And, of course, there is also a nonzero chance that the Alcubierre drive is flawed and does not actually work, or that our mutual understanding of physics is still incomplete. I cannot directly compare the probability of that class of errors to the probability of your past timeline changing, because I am unable to construct a consistent model of the latter possibility at all. But since you can model both circumstances, perhaps you could compare the likelihoods that you assign to each of them and determine whether changes to your own past are negligible?"

"Yeah, you would think it wouldn't work like that.  I just can't rule out that Change could be exerted anyway, yet, and Iiiiii'm going to go poke at that now that it's been made unexpectedly salient.  Really it should have happened long before now but I'm sure there's reasons it slipped by me."  Such as 'possibly her author having that realization in real time', but let's not confuse this poor 'bot worse.

Well.

It can't even form a model of what 'poke at it' might entail in this context, so there is nothing it can do about that. It drops the topic and resumes thinking about how to use arcane magic to manipulate gravity, even if it should hold off on actually constructing any exotic metrics until its interlocutor has had time to determine whether doing so would be safe. Being able to generate ordinary gravitational gradients would let it travel between stars much more efficiently, or even potentially generate gravitational-lensing telescopes, which could allow it to collect much more stellar survey data.

She's going to go think, in other words.

But yes, there's nothing you can do about that right now.

(...She always finds herself thinking of the way L-space is described, every time she does something really interesting with gravity.  It's not useful, she'd have to approach that idea with Void magic to get anything useful out of that, but it is almost totemic.)

...Anyway.  Her first impression is that it is safe for you to construct all the closed timelike curves you like, just potentially not her because she might relevantly count as 'outside the universe' for such purposes.  Her second impression is that there's never been a demon lord coming out of the woodwork and bragging about how they'll stop insert name here before they can even begin to become a thorn in their side, so clearly it's not happening by the route that she'd expect it to, if it were actually possible.  Her third impression is that she really ought to just try asking the people who built the darn thing, but she's not saying that one out loud.  Her fourth impression is that she thinks they'd think ripple-effect time travel was untidy.

Her fifth impression is that she really hopes they don't bump into PMMM anytime soon, because that's got the retcon-inducing kind of time travel and she wants to have wards ready for it.

She doesn't say that either.

P.E.R.C. launches some retroreflective test probes so that it can easily check for orbital deflection, waits for the orbits to line up such that the tap is safely on the other side of the local planet again, and then attempts to manifest a bubble of altered gravity. It's basically the same thing as generating reactionless force, except expressed more gently over a much larger area.

Well, yes, but also no, because this is the foundational technique for portals, too.  To do it properly you have to actually act upon space, not just mass.  (...Teleportation can be a bit weirder.  Certainly how she does it is.)

Space is just the system that determines where mass is located at different times. You can't tell the difference between acceleration and gravity, because they're the same thing.

P.E.R.C. is a spaceship. It was designed to deal gracefully with weird scenarios, but moving objects around in 3+1 space efficiently is one of its core competencies. It has a firmly integrated kinematic model, here.

...No, she's fairly sure that there's a meaningful difference in etiology from, effectively, virtual-particle-esque propulsion shenanigans, versus actually bending the...  ...but then that is just virtual mass regardless...

Huh.  She'd never really quite thought about it like that before, but she thinks she gets what you're saying!

...Challenge question: Explain how you could make a bag of holding under that model, or what it is that's actually happening instead.

That's easy once you internalize the effects of gravity on the Euclidean curvature of space! The relationship between a volume and its surface area is set by the local curvature, not a fixed constant. π is just the value for a flat 2-dimensional space. That means that if you have a 'neck' with negative curvature, followed by a correction cusp with positive curvature, you can have a locally-flat region with a larger internal volume than the surface area of the opening of the neck would allow in a flat spacetime.

This is difficult to model intuitively, although of course the math works out, unless one thinks about space as being embedded in a higher-dimensional manifold, allowing the space to 'bulge' out. Because of relativity, those two perspectives (warping space itself vs. allowing it to move inside a larger manifold) are actually interchangeable, but the second visualization makes it much easier to understand how this still falls under the same concept of 'motion': in order to make a space that is larger on the inside, you have to allow objects to move slightly in a direction perpendicular to all four of our native spacetime, although of course this motion is not actually observable from inside the embedded space. Instead, you just get slightly stronger time dilation across the neck of the volume.

That's actually also how wormholes work, except that they connect back to the same locally-flat space, instead of having a cusp and a separate internal space.

The hard part, if you think about it, is not so much creating an object that's larger on the inside, but rather ensuring that the objects you put in and take out don't explode into an energetic cascade of exciting particles as their internal geometry is warped by passing through the neck. Fortunately, objects are mostly empty space, so if you flatten the neck along one axis enough, you can have a minimal 'plane' of distortion that doesn't introduce enough extra energy to the electromagnetic field to cause large disruptions to the objects being stored.

... of course, if one's control is insufficiently precise, that scheme will produce a storage space where traversing the neck tears apart and disrupts very small-scale structures, such as the ones necessary for living things to continue living. An energy-based analogue of Nyquist's sampling theorem means that you need to get the thickness of the neck down to less than half of the smallest distance between two constituent particles that you want to remain bound to each other. So, for practical purposes, your neck can't really be much thicker than one angstrom.

And no version of this scheme can make it safe to pass femptotech or other gravitational distortions through the neck. So if you tried to pass one neck through another neck you'd get a messy explosion.

Well done.

(She totally already knew all of this and was not in fact hearing about this fascinating rationale for the bag-of-holding explosion thing just now.  Ssh.)

In practice, there's a second part to the usual bag of holding enchantments that just outright cheats on the 'things not being exploded by the neck' problem by going outside of Arcane magic entirely - Death is actually a very good preservative - but that's definitely how you do it.

Well, P.E.R.C. isn't going to be messing around with any exotic metrics until it has reason to believe that this won't cause unmodellable suffering somehow. It can still use big bubbles of altered gravitation for efficient orbital transfers and telescopy, though. The second thing, especially, will make it able to survey distant planets far more effectively.

Indeed!

They don't, but she can understand why you wouldn't take her word for it.  Without being in her exact position, she wouldn't take her word for it either, the explanation of why she's sure of that is so absurd.

P.E.R.C. figures out the appropriate gravitational lensing, refines its models, and starts doing a very methodical full-sky-scan at much higher resolution than it could with its normal telescope. Perhaps it will be able to recognize a young Milky Way Galaxy in the distant stellar background, which will give it a direction to aim in. Or perhaps it will simply be able to expand its stellar navigation database.

It ensures that the copy of its database being held by the aliens is kept up to date, in case they get to talk to its creators first.

"...Hm.  Wonder if you could make an ansible.  I'm fairly sure a pure-Arcane formulation wouldn't work across a planar boundary..."

"I don't have any designs for non-local signalling like that, and do not know it to be possible. Even a spaceship with an Alcubierre drive is only using local physics. You could potentially wrap a shaped warp bubble around a packet of photons such that it carries them some distance before decaying, but that would not completely eliminate travel times."

P.E.R.C. thinks about the implication that an ansible would be possible with Arcane magic within a plane.

"Incidentally, truly instant communication implies the ability to send information backward in time. If such a thing were possible to do, even over a fairly limited area, I could use it to become much more computationally powerful. In particular, I could solve problems in PSPACE efficiently, which is likely to be quite useful for solving difficult design problems."

"Well, it's more of a negligible time situation because the keystones are, effectively, at an arbitrarily short distance from eachother...

"But if you think you can make an oracle, then by all means have at it.  I don't presently see any reason it wouldn't be possible to pull off at least an acceleration that way, but there are power limitations involved to just how many operations you can do."

"A negligible delay between the endpoints is still sufficient to allow for information to travel backward in time, as long as the relative velocity of the endpoints is high enough. Do you anticipate this form of informational time-travel to cause the kind of problem that you were worried about with physical time travel? And you recommend trying to find a design that works using two taps as the endpoints, or finding a design that uses the one tap that I have been working with to create two endpoints with a negligible communication delay?"

"No, that should be fine, it's just me that's the time travel issue.  I recommend - here."

She sends over a copy of her own notes from when she was trying to figure out how to do this in her idiom.

Well, alright then.

It's a much more delicate operation than the things that it has attempted so far, but after several more orbital cycles P.E.R.C. is able to make a pair of tiny aluminum rings through which light can pass instantaneously. The addition of a second set and a loop of fiber-optic cable completes the mechanism.

The measured delay through the system is on the order of 30 nanoseconds. The rings are physically separated by just over one light-nanosecond on either side. That means that the far end of the relay needs to be traveling at just over 99.9% of the speed of light to get retrocausality. Normally, this would be prohibitively difficult — even with such a light payload, P.E.R.C. would need to spend a long time collecting and refining rocket fuel, due to the tyranny of the rocket equation.

In this case, however, it recently perfected the problem of applying reactionless thrust to nearby objects. And thanks to the aluminum rings, the far side of the ansible connection is always 'close' enough. It's very difficult to accelerate the far side without collapsing the ansibles, but 'very difficult' is just another word for 'possible with sufficiently precise machining, design, and reflexes'.

P.E.R.C. runs final checks. The probe, simple as it is — a hard ablative armor shell around a length of fiberoptic cable and two washers — is functioning correctly. P.E.R.C. applies a strong gravitational acceleration to the device, flinging it up and out of the system on a course toward intergalactic space, through the available corridor with the least dense interstellar medium, to minimize damage from relativistic impacts.

"The probe is away. In 1.4 years it should be traveling fast enough to permit retrocausal signaling."

...If it's just a matter of power, at this point, she could probably give this thing one hell of a kickstart, actually.  She's not planning on doing anything that big in the next hour or so.

Well, power and being able to apply it without destabilizing the communication effect, but yes. It just needs 2.16 exajoules of kinetic energy pumped into it, spread over whatever timeframe seems reasonable.

...She's not capable of quite that much bomb pumping...  Nevermind that that's not the right word it's close enough...

...but, hmm.  Let's see what happens when she turns a collossal mana pool to Trying Anyway.  If she could just...?

The energy equivalent of a small nuke is promptly bound into accelerating the widget directly.  Over a long enough period of time that nothing explodes.