The Speed of Magic?

Fair warning this is a stupid hypothetical that has little practical bearing on the game, and that pokes at weird edge cases of the magic system that are probably best answered with "it's a game, you're overthinking things". That said, if the questions are left open ended it could be useful as an ongoing experiment by an NPC Bonisagus - an interesting sounding project that never yields any definite results. Continue at your own risk.

The Setup
Imagine the following scenario: we have an item, lets say a cube of metal. The cube is a greater item invested with several effects:

  1. A constant effect which detects if the cube is in a magic aura.
  2. An effect which transports the cube one pace in a fixed direction, with a linked trigger to make it happen if the cube enters a magic aura.
  3. An effect which transports the cube one pace in the opposite direction to the previous effect, with a linked trigger to make it happen if the cube leaves a magic aura.

All effects have unlimited uses per day.

The Experiment
Imagine we take this cube and walk to the edge of a magic aura.

We throw the cube gently into the aura. This triggers effect #2 which instantly transports it a pace back, across the edge of the aura.

Having left a magic aura, effect #3 is triggered. This sends the cube a pace forward again and into the aura.

This triggers effect #2, sending the cube back out of the aura... and so on ad nauseum.

The Questions

  1. Does this experiment work as described? Does the cube actually oscillate back and forth between two positions?
  2. If the above is true, what is the frequency of the oscillations? This breaks down into a few smaller questions:

Is there a measurable delay in the cube sensing the aura information? The cube has been granted a supernatural sense, but in living beings there is a delay between information entering the senses and reaction - is there a similar (but usually imperceptible) delay in enchanted items?

Is there a limit to how quickly an effect can be triggered? In game terms this is probably limited to once per round - but is this actually a fundamental limit of magic, or just a game convention? Perhaps an atom of time is this fundamental limit (defined as 1/564th of a moment, which itself is 1/40th of a solar hour, or 15/94ths of a second) as this was considered to be the smallest subdivision of time in the 13th century.

Is "instantaneous" transportation actually instantaneous? Or like the sensing is it simply so fast as to be usually imperceptible?

Perhaps more importantly: If the idea works, is there a practical application?


There is the so-called Maxim Wand, named after a young but technically minded Flambeau.

Maxim put two enchantments A and B into it: two Pilum of Fire with Unlimited effect frequency and linked triggers: if A fires, it triggers B - and if B fires, it triggers A.

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I assume they were invested in the same season?

This is the first answer I’d use in my own game. I could be persuaded out of it, but this is the answer according to the rules.

base rule- one spell per action.
an action is roughly 6 seconds (p. 112 of the core book, diameter is defined as 2 minutes or 20 combat actions). Ergo it would teleport back and forth with a full cycle taking 12 seconds.

yeah but this is a gamey sort of way to resolve it. I agree that if it ever happens in a game that my players want to do this during combat that is how I would rule.

But I think from a theoretical point of view @Argentius has a point about 15/94ths of a second, assuming that he/she is right about 13th century ideas about time. Which I have no idea about and thus cannot back up or deny.

That would be really strange because

  1. horology (study of time) didn't have a good definition of a solar hour until late middle ages at minimum and didn't have an accurate method of measuring it until the 20th century.
  2. the numbering system for days and hours was of sumerian orrigin based on a numbering system which fundamentally used base 60 (it actually used a combination of base 6, base 10 nd base 60 which only makes sense when you are counting on your fingers and leaving a mark when you reach 6 or 10) This is why there are 60 seconds to a minute, 60 minutes to an hour, 360 degrees in a circle (6x60) and 6 hours for a quarter of a day.. To switch to a biblical based number such as 40 would make sense for a medieval theory, but wouldn't be consistent for an underlying cosmology.
    I have no idea where the 1/564 would have come from aside from this wiki article; Atom (time) - Wikipedia
    I would also point out that one person's theory does not make it the prevailing opinion of the middle ages.
    Fundamentally however, if you do use this method to find a fundamental frequency which defines the smallest unit of time, how would you measure it? Using Medieval timekeeping technology to try and measure this quantity would be like trying to determine the size of a molecule with a wooden ruler.
    Of course serious fun as a SG would be to have something where the answer is different depending on the strength of the aura.


As for the OP, I don’t think Auras are fixed, absolute boundaries, like the edge of a cliff. I think of them as a field of variable intensity that we measure in discrete chunks for convenience and playability (if people are upset because they have to divide by two when sponting try saying them that they have to resolve a differential ecuation to get the current aura).

So, if that Bonisagus were at my table I’d probably have the box jumping over and out at random times, according to the fluctuations of the area. Which would make it a pretty good item to know when an aura is getting affected by something.

And so I guess the Bonisagus would come back with a cube that jumps not 1 meter (the through the muddy border of the aura) but 50 or something like that (which would be good because now we really are talking about an experiment that can break stuff all around).

As for time and it’s research when Galileo invented a reusable, fixed clock he just made a pendulum bounce around noticing that the only difference to the time it took it to pass through the vertical point depended of the length of the pendulum: it is not that you even need a breakthrough, just to be brilliant and very bored in a big church.

Is it really 1/round canonically? I had the distinct impression there were linked MuVi effects in items and that the basic effect was just modified, but went off the same round as triggered, which would mean both the basic effect and the MuVi effect go off in the same round.

In this case you're waiting for one effect to end to start up the next one, though, rather than both stacking off the same single initial trigger.

This is my favorite answer, as the most in keeping with the world.

My own first instinct would have been some kind of decaying oscillation, which is wrong since there is no reason to dampen the motion. So either random jumps, or some kind of step function where the box alternates between being not quite a full length in to not quite a full length out.

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Other possibilities to throw your players:
The box jumps to where it is half in and half out of the aura.
The box is located both 1 pace inside the aura and one pace apart, though it is still only one box, and anything you do to either one affects both manifestations.

Solar hour is maybe a bad way to phrase it, in this case I meant a 1/12th division on a sundail (so 1/12th of Sun duration). This is not a fixed unit of time - but neither are most hermetic durations. This division is a well established part of the reckoning of time at least by the time of the Venerable Bede who writes about it, and the atom, in De Tempore Ratione

The atom is simply the smallest possible division of time, Bede doesn't give a value for it and essentially dismisses it as a pointless endeavour to try and find one. The 1/564th is given first by Byrhtferth of Ramsay in his handbook on the computus (technically he gives it as 47 atoms make up an ounce of time, that is 1/12th of a moment), and is used sporadically in other works after that - but I'm not sure where or how the value is derived and I don't have access to a translation to check if he gives one.

Regardless of the specific value, the idea of an atom as some theoretical indivisible smallest time unit is well attested back into the early middle ages. Byrhtferth's value could just as easily be substituted for any other arbitrary number in a saga - this magical experiment would be the sort of thing that establishes what that value is to magi. And of course the unit will vary with the motion of the sun, so really it's maybe better to think of this as the smallest possible spell duration in hermetic terms rather than a fixed value unit of measurement.

Fundamentally however, if you do use this method to find a fundamental frequency which defines the smallest unit of time, how would you measure it ? Using Medieval timekeeping technology to try and measure this quantity would be like trying to determine the size of a molecule with a wooden ruler.

This one has a pretty simple answer I think, you wouldn't try and measure the time of one oscillation but rather the number of oscillations in a fixed period. Add an effect that creates an acorn every time one of the other effects is triggered, and then counting the number of acorns generated between sunrise and sunset tells you the number of atoms in Sun duration, with a little bit of error. Take several repeat measurements to average out the error and you'll get pretty close. Or perhaps this fails and the fundamental unit doesn't seem connected to solar cycles at all - that would itself be an interesting outcome.

Though for that to work the acorns would have to last moon duration and that means by the time a month had passed you would have something like 16 million acorns lying around. That's an amusing experimental side effect.

You know I never considered it that way but this idea makes a lot of sense, and it raises other interesting questions too - for example, there is a certain point where the effect detects "I am in an aura", but where is the line exactly? Is there such a thing as fractional aura levels, and could a more powerful InVi spell detect them? Not that they'd be useful for much, but a Bonisagus might still want to find out.

Now there's a story seed in that - Bonisagus character sets out trying to find out some escoteric detail of spell durations, ends up accidentally creating a sort of aura seismometer. Very true to life that something very useful comes out of an experiment trying to find out something totally unrelated. "Huh, that's weird..." is far more common than "Eureka!" in my experience.

Interesting idea, and there's a certain logic to it - if there isn't a limit to how fast the effects can happen (and there might not be) then it seems plausible they would sort of superimpose on each other. Seeing as the effect is a ReTe one you could maybe tie this strange effect to Mercere Portals - maybe they are a more practical application of this, superimposing two archways so that they sort of exist in both places at once, regardless of the distance between them.

Maybe the reason Mercere Portals don't warp things passing through or need any requisites is because the magic just creates the superposition, but walking through from one place to another doesn't actually subject the person to the effect - only the portals themselves.

Could be an interesting line to go down. Links it in with an established but mysterious magic and also opens up plot hooks for conflict with house Mercere.


let's assume that your calculations were correct and the box was generating 15 acorns every 94 seconds, as calculated by sun duration, and that furthermore an atom of time varied seasonally and with latitude so this was a consistent effect- bending my suspension of disbelief to the breaking point, but consider the supposition: at the end of sun duration you would have 6893.617 acorns, meaning that even with this supposition the number should vary between 6893 and 6894 acorns in a day.
Now, imagine the poor apprentice or grog assigned to count these acorns. What is the probability they will count accurately?
Of course you can substitute InHe to count for you, with a group size+3 or four for the number of acorns, but at this point you are substituting magic for technology to break the setting...

and that furthermore an atom of time varied seasonally and with latitude so this was a consistent effect- bending my suspension of disbelief to the breaking point

I'm not sure what suspension of disbelief is needed here? That's just the nature of timekeeping prior to mechanical clocks. Measuring time by the sun and moon necessarily means that every time unit varies somewhat with astronomical and geographic factors and that the nominal value is just the average value. Every time unit is just a division of a day or night, and the length of day and night aren't constant.

but that aside, I don't think the counting is really a significant problem. Hermetic magic can easily time a diameter using the expiry of a spell. Catch the acorns in a bucket and count how many you get in a diameter (something in the order of 600). Check the work. Repeat a few times a day and average. Repeat every day for a year, maybe do this for a few years if you're being really thorough. The more measurements you take the less individual errors matter, by the time you have 1000 or more the odd miscount is statistically insignificant.

A lengthy research project for a magus for sure (well, more so for a numerate grog that takes the measurements) but no part of it is out of the ordinary. It's no more mathematically complicated than what mundane astronomers, mathematicians, and natural philosophers were up to in the 13th century. The magus just has access to a measuring device that they don't.


I think the biggest issue is simply with the idea of a world where people's expectation of how the world works is perfectly correct and yet people continue to take such extraordinary steps to conduct experiments to confirm it centuries before the invention of the scientific method...

The first one makes me think that now both the effects are working wrong, which is odd.

The second is dangerous because it makes you able to clone stuff; you can get two copies of an object by doing that. Also what happens if then you take any of these two copies of the object and toss them over the Aura edge? You should get then 3 boxes. And so on.

Two more options anyway:

  • The object breaks in two pieces, with one chunck at each side of the Aura.
  • The object explodes in a rain of fast metal shards (I like this one!).
  • Nothing happens.
  • Nothing seems to happen, but if you InVi the cube it seems that a lot of stuff is actually going on and we don't know what.
  • One effect overrides the other either always or most of the times (I like this one, because I also like to think of spells not so much as infalible, exact iterating magic equations than cooking recipes where if you try two times the same thing with the exact same ingredients you end having two similar but not exactly equal things).
  • You create a Regio with two entries: you seem to end with two cubes, but they are actually in the same place, is just that the two spots where you can see it are two entries to the regio.
  • The item disappears (maybe also in a regio, but not visible nor accesible).
  • If you repeat the experiment, different things of all of the above happen.

Diameter durations, which you also mention, are actually quite stable. They do vary because the sun's distance isn't fixed, but not that much.

Also varying durations don't have to be a problem as long as you know how much do they vary; it is just a matter of knowing your latitude and longitude and the time of the year, and then it is just something you can tackle with a bit of Artes Liberales, for Astronomy and Geometry.


Reading this thread makes me want to include this cube in my game.

I will at some point have the party go dumpster diving exploring the labs of a now deceased maga. But then I will make it a Boniagus who trie to answer this question empirically. So there will be a metal box stuck hovering on the edge of the magical aura, and as the players try to remove it it just goes back to its old position...

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Please consider, that there is a difference between a smallest measurable unit of time, and the smallest possible division of time.

For Bede, the practical schoolmaster of early 8th century, this difference may not be very interesting.

But Aristotelian and scholastic philosophy, linking time to motion (Physics iv 10–14) and not having a smallest possible division for motion, has also none for time.

I suppose this depends a little on how strictly you apply the mythic paradigm in your saga. Personally I've always applied it to the broad strokes, but left most things that are uncertain, obscure, or generally on the cutting edge to knowledge in the period as more open for debate. It gives empirici and Bonisagi something to do...

And of course rule #1 is that if it would be interesting to not apply that paradigm to a specific thing for purposes of story, the story comes first. But that's only my own preference.

However about the scientific method I have to disagree that it's especially hard to believe. True, the scientific method of later years wasn't yet codified, nor were the ideas that would give rise to it the primary mode of thinking among academics in 13th century Europe - but that doesn't mean those ideas didn't exist at all. After all we don't need it to be believable that every academic in Mythic Europe is performing these experiments, just that one Bonisagus has had the idea to.

Aristotle's Posterior Analytics has the seeds of Empiricism in it, and has been available in Latin since the mid 12th century. Multiple Islamic writers have espoused ideas in this vein by the 13th century, and in the Latin West Robert Grosseteste and Roger Bacon both describe and apply empirical observation and a crude kind of controlled experiment within the timeframe of an Ars saga.

Empirical observations were not yet the primary means of reaching scientific conclusions (far from it), but they were used (alongside other methods) by some academics. I think it's totally plausible a Bonisagus has access to the same knowledge that led those thinkers to use empirical observation. Doesn't mean it's a widespread practice.

Maybe if you try to do something like that it causes one of the other options you suggest? Initially it seems stable but then if you go "what happens if I...?" you get an explosion, or the effects just stop, or it simply vanishes...

I really like some of your suggestions, especially the idea that it it maybe isn't a consistent result and you get different outcomes depending on all sorts of environmental factors or even seemingly at random - that's the kind of thing that could drive a Bonisagus mad (in a good way, story-wise)!

I didn't mean to imply that the atom as an indivisible unit of time was a foregone conclusion or anything, only that the idea existed and was espoused by some thinkers in the period. And it is definitely used to mean "the smallest possible division of time" (hence the name atomus, "indivisible") as it pops up sporadically from the early medieval right into the 16th century with a "known" value, despite the tools to measure it having never existed. Even the next unit up, being the ounce, wasn't really measurable either even by the 16th century.

Again, not to say that that means it's correct in Mythic Europe, only that the idea existed so it could be correct, in theory, and the Aristotelians are wrong.

I think it's equally plausible that (as in Aristotle) there is no such fundamental unit in Mythic Europe and then you get the weirdness of both effects happening simultaneously as we've been discussing in some of the posts. An equally interesting result. Comes down to an "in your saga" decision really - what seems like the more interesting answer?