"A Matter of Principals" Afterthoughts: Equestria's Arcane Detectors and their Potential Usage · 12:27am Aug 8th, 2018
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"A Matter of Principals" introduced us to a nice little bit of worldbuilding for Equestria: Arcane Detectors!
During the spellvenger hunt, the students of Twilight's school used little, wristwatch-like devices to find the magical artifacts that were hidden in the school. These arcanotech (= technology infused by magic) devices were able to detect the magic inside the artifacts and to react on them; every time they got close to one, the two tiny spheres on them aligned and began to glow red. Then checkmarks appeared on them once they moved the arcane detectors in front of the artifacts.
So, Equestria has arcanotech that allows ponies to find sources of magic, by detecting the magical signatures in objects and ponies or other magical creatures. And, obviously, these devices were not specifically created for Twilight's school, but have already existed before, and are probably even mass-manufactured since Twilight ordered many of them for her students, so I sat down and came up with a few things these arcane detectors are potentially used for in Equestria:
1. The discovery of magical artifacts
The most obvious one first, that we already saw in the episode. The arcane detectors react to any kind of magic they detect, which makes them likely getting used by treasure hunters and adventurers to find hidden, magical artifacts. Maybe even Daring Do uses one of them to aid her in digging up artifacts and relics she is looking for.
2. Finding lost ponies/unicorns in a crowd
Imagine the following situation: It is a busy day in Canterlot and you are hanging out with your unicorn friends; talking, shopping, eating, having fun. At some point you split up and each of you does their own thing, but you want to meet each other again in a few hours. But how do you want to find your friends again in the huge crowds that move through the streets and without knowing where they are? That's where your arcane detector comes into play.
Before you split up, you adjusted your detector to the magical signatures of your friends and your friends did the same with their detectors. Having saved and remembered the magical signatures of your unicorn friends, your arcane detector always knows where they are and will inform you once you are near them, so that it is easy for you to find them again.
The same procedure could work for non-unicorns, as even earth ponies and pegasi carry some magic in them.
If every pony has a magical signature that is unique to them (which is now definitely my theory, now that we got introduced to these magic-detecting devices), then finding other ponies is definitely one of the reasons why Equestria invented these arcane detectors.
3. Repairing other magical devices and magical machines
I can also see these arcane detectors being used in an industrial way. What if a machine that runs with magic suddenly stops working or malfunctions? A likely reason for that is that something is wrong with the distribution of magic inside of it. Maybe there is a leak somewhere and the machine loses magical energy that it needs to run or a pipe inside the machine that transports the magic is choked-up?
But the machine is so large that manually searching for the problem would take days? Then a repairpony or technician can use an arcane detector to find out where magic leaks out of the machine or where magic is jammed inside the machine because it is blocked from flowing by something.
This allows the repairpony to find the problem and take care of it swiftly and efficiently.
4. Solving crimes
Coming back to each pony having a unique magical signature this also means that this signature can be found at places where a unicorn cast a spell, via the traces of magical energy that stayed behind after the spell was casted.
If a unicorn would break into a shop at night or even kill somepony, by using a spell, then the arcane detector can be adjusted to the magical signature in the traces the unicorn left behind and investigators, police officers or royal guards only have to go around and check the ponies they meet. Once the spheres on the detector align while being pointed at a unicorn, they have found the culprit/suspect and can arrest them.
This doesn't work for pegasi and earth ponies, because their magic is passive and never leaves their bodies, but a unicorn who committed a crime can easily be found that way which makes solving crimes, at least as long as unicorns have committed them, an easy task in Equestria.
Maybe Equestria's authorities even have databases with the magical signatures of known unicorn criminals, so their signatures can be identified at the crime scene if they committed a crime again.
5. Medical usage
The same that works for machines, could work for ponies too. If magical afflictions, that cause problems for the body, exist in Equestria, one of these arcane detectors could be used by a doctor to scan the body of a pony patient and find out where the magic doesn't flow properly or is interrupted.
This is a little vague and a bit more on the theory side, as we don't know if magical afflictions like this can happen to ponies, but it is a possibility and, therefore, another possible usage of the arcane detectors.
These are five purposes Equestria's arcane detectors are likely/possibly used for. I'm sure there are also many more potential usages for them, but these five came to me off the top of my head.
I might think of more one day and write another analyzis like this, but if you can think of any other purposes these arcane detectors might be used for in Equestria, feel free to write them in the comments!
These could be adapted to create an early warning system in case yet another ancient evil awakens and is going to try and take over the world. The devices would detect a spike in powerful magic and then get the authorities in each town to start emergency evacuations to prepare for whatever is coming. Would be a lot more of a warning than what Celestia usually gives.
4917420
That's an excellent idea! Most ancient evils or villains who broke free or invaded/infiltrated did so on a very short notice and also in a way that nopony in Equestria could see coming. The only exceptions were Nightmare Moon (least at her first return), which Celestia knew about and made preparations for, and King Sombra's return together with the Crystal Empire, which Celestia didn't know about, but evidently made preparations for anyway.
A warning system like this would make Equestria a great deal safer from such threats.
4944092
It could also probably be used to detect magic from powerful artifacts so that they could keep tabs on creatures like storm king and ahuiziotal. There’s a lot of really fun ideas that could bloom from this one device.
4944115
Indeed. I think I should open a thread about them in the Writer's Group at some point, they offer a lot of very nice opportunities and potential for fanfics and I'm not sure if pony authors and the fandom at large have paid much attention to them so far.