Based on a set of questions by Pavel Janicek about how to address and then monetize magic mirrors in today's modern world.

The short version of these magic mirrors is that any one magic mirror can make a 2-way connection to any other magic mirror by the user asking their mirror to connect to another mirror by its unique name.

Many of the answers to the monetization question suggest using mirrors to replace wires/fiber-optic cables/radio signals in current communication technology. The magic mirrors as described appear to:

  • Not use any power (no apparent power source involved, no apparent degradation from use)
  • Not have a limit on range (tested at 1500 km apart)
  • Transmit both vision (which we've all assumed means light, the full EM spectrum) and sound in high or perfect fidelity
  • Not require an infrastructure like wires or cell towers to carry a signal between mirrors
  • Understand natural language in at least 5 languages and presumably any language spoken by a human
  • Require a unique name, which can be any unintelligible combination of syllables, leaving an absurdly wide address space.
  • Understand and correctly interpret drunkenly slurred as well as computer-generated speech. (They may possibly interpret unspoken intent in the speaker's mind, further testing is required.)

Magic mirrors can be created by an intelligent lay person (possibly on their first attempt; this was unclear) with $50 of materials and equipment in two hours' time. Those costs and requirements leave a huge potential for manufacturing optimization.

The first modern maker of these mirrors, Pavel J., discovered some ancient documents in Baba Yaga's house detailing how to make them. He has created a small number of mirrors and done some basic tests of their abilities. As with any other new technology, there are often limitations and/or drawbacks which are not apparent when the technology is first discovered but which become apparent as the technology becomes widespread. For example, radio signals have a practical limit to how many overlapping signals can exist simultaneously before they start interfering with each other. It wasn't an issue 100 years ago, but it sure is today.

What subtle limitations can be applied to how these mirrors function so that they are still quite useful, but not so overpowered that they turn civilization on its head?

Good answers will have one or more limitation which

  • would not be immediately obvious to a lay person testing a handful of hand-made magic mirrors.
  • would not curtail the mirrors' abilities so much that they become useless or worthless if patented and mass produced.
  • will keep magic mirrors from directly causing modern society as we know it to cease to exist.
  • is not easily overcome or bypassed (eg the mirrors output cancer-inducing radiation; easily overcome by adding radiation shielding).
  • can't be misused by a mad scientist to easily destroy the world (eg duplicating photons in a loop to instantly create massive amounts of energy from nothing).
  • (ideally) resolves magic mirrors initially appearing to break the 1st Law of Thermodynamics. (Note: perfect efficiency is ok, just no energy coming from nothing)
  • cannot itself result in destruction of the world as we know it.

Answers will be judged on subtlety, simplicity, and robustness:

  • Subtlety - is the drawback difficult to notice in initial tests? Would it have no appreciable effect on ancient usage?
  • Simplicity - is the drawback fairly simple to explain and understand?
  • Robustness - does the drawback just introduce new plot holes or break physics in new (if interesting) ways?
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    $\begingroup$ How are you going to assess one answer’s worth over another? Don’t get me wrong, I like the question, but as it stands it’s Primarily Opinion Based (IE we have no way to judge what is a good/better answer in your opinion) $\endgroup$ – Joe Bloggs Oct 9 '18 at 20:22
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    $\begingroup$ Overpowered? Could you maybe emphasize what is in your view the material difference between those mirrors and solar-powered Iridium phones? They don't require a source of energy other than the sun, they can connect to any other Iridium phone in the world, the infrastructure they use is not on this Earth, they transmit pictures and voices... $\endgroup$ – AlexP Oct 9 '18 at 20:30
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    $\begingroup$ You can judge it by realistic-ness, being difficult to notice with normal tests, and simplicity. $\endgroup$ – John Locke Oct 9 '18 at 20:31
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    $\begingroup$ @Shule I tested these mirrors. Patent is already granted if you want to ask $\endgroup$ – Pavel Janicek Oct 11 '18 at 7:39
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    $\begingroup$ Why do you care about thermodynamics? You can get free energy from your magic mirrors, but you can also get "free" energy from the sun, and much more of it. For the purposes of your society, there's no difference. You already have to tweak physics a bit for anything magical. $\endgroup$ – Obie 2.0 Oct 12 '18 at 5:16

21 Answers 21


Magic Mirrors require a focus -- they need to be directly in front of a living being in order to maintain their connection. Some say this is because they are draining part of the soul of the person (or, in some cases, animal) they are centered on, others say that it's like a computer timing out if nobody moves the mouse for a while.

Functionally, this means you can watch somebody while they sleep, but you cannot connect to a mirror in outer space intending to pull unfiltered sunlight. Yes, you can move sunlight from a desert to a dark area, but only if you have someone standing around in the desert to be your mirror focus. And while they may get paid to be the focus for a few dozen mirrors at once, it's a hot, boring job, and that one time they needed to step away to go to the restroom, they got fired...

This was especially frustrating for initial testing inside computer parts -- the engineer sets everything up, it's running perfectly fine, and then he walks away and it shuts down. A machine correctly connects the LEDs to the mirror, and it won't boot up until the tester comes over and stands in front of it.

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    $\begingroup$ Does "living being" include a tardigrade in stasis? If so, you could still put a mirror in space with a small cargo tote of them in front while still allowing in loads of sunlight. Perhaps the requirement should be that the living being also focuses on the mirror. This would remove any such tricks but would also prevent watching people while they slept. $\endgroup$ – Engineer Toast Oct 10 '18 at 15:40
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    $\begingroup$ Call me cynical, but I don't think that modern capitalism would be above hiring people to sit in front of their mirrors all day to facilitate the high speed internet described as an answer to the other question. Indeed, if a telecommunications company can replace a team of skilled engineers maintaining a data centre with a few rotating shifts of unskilled people who sit in front of the mirror for a few hours at a time and maybe read a book or something, I think they'd leap at the chance. $\endgroup$ – ymbirtt Oct 10 '18 at 15:45
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    $\begingroup$ @ymbirtt the magic mirror needs a line of sight to the focus's face. If you use your mirrors for communication, you'll need to design around that - stacking multiple mirrors in sheets will become rather difficult. $\endgroup$ – John Dvorak Oct 10 '18 at 20:02
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    $\begingroup$ @EngineerToast While I'd be inclined to say the mirror requires either a certain amount of brain activity or a powerful enough soul to keep it focused (depending on magic's proclivities), I have no doubt the Magic Mirror Research branch that develops would eventually figure out exactly how many tardrigrades are required to power a square inch of Magic Mirror, if it's at all possible. $\endgroup$ – Chelsea Oct 10 '18 at 21:37
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    $\begingroup$ It makes sense that a mirror would drain the users to maintain the connection. So spying on a sleeping person would require more effort and you would tire more quickly than if both sides have active participation. This way, every user is limited by his own stamina (and magic proficiency - a powerful wizard could maintain connections on multiple mirrors with ease). If you fall asleep in front of a mirror, it shuts down unless the other person is focusing on it. $\endgroup$ – orion Oct 11 '18 at 8:29

One of the ingredients of the magic mirror is:
- Half pint of blood of the maker.

Baba Yaga is a witch (as far as I remember), so it may sound logic she included some creepy ingredient in such a wonderful invention.
So the fabrication of the magic mirrors is limited by the amount of blood able to be retrieved from the makers in a month.

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    $\begingroup$ Nice, hadn't considered this possibility. Could a computer-guided animal "make" mirrors? Technically we could say the animal is a cyborg before it's, uh, stripped of its augmentations and slaughtered for food. Since Baba Yaga's own mirror is still functional we can assume mirrors remain functional after their creator's death. Alternately, could a mirror maker use transfused blood that has passed through their veins at least once? Does the quantity of blood required scale with the size of the mirror, and/or can multiple mirrors be manufactured using one batch of blood? $\endgroup$ – Martin Carney Oct 9 '18 at 20:37
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    $\begingroup$ We could thinkg the original receipe (half pint of blood) was for a mirror of the original size found in Baba Yaga´s house. A bigger mirror may need more blood (like a cake receipe). The blood of the maker is what creates the "master link", so no one can program the mirror (telling the mirror who to communicate with) except the one who gave the blood. And since the blood itself has a link to its owner, I don´t think transfused blood may work the same. Just the blood that was "born" inside the maker. And yes, an animal could provide the blood, but the mirror will only obey the animal :) $\endgroup$ – Carlos Zamora Oct 9 '18 at 20:44
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    $\begingroup$ I'm picturing slaughterhouses being modified to temporarily install a computerized voice box into cows, drain their blood, and "speak" to batches of mirrors manufactured using the blood. ("It's not animal cruelty because they lose consciousness before they're slaughtered.") $\endgroup$ – Martin Carney Oct 9 '18 at 20:51
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    $\begingroup$ blood must come from a creature that can potentially understand the language that is spoken to the mirror. Additionally, the blood is the fuel that makes the mirror work. 6months of continuous usage and the mirror is useless. $\endgroup$ – Michael Kutz Oct 9 '18 at 22:42
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    $\begingroup$ @CarlosZamora I am afraid, that the author found mirror made by Baba Yaga and used it just by saying the address, before creating its own, so "master link" is not needed for usage, just (maybe) for creating (and/or) naming new one. $\endgroup$ – gilhad Oct 11 '18 at 0:45

For resolving the issue with thermodynamics, the magic mirror shouldn't be creating new photons, or changing their arrangement at all. The mirror simply receives photons here and outputs the same exact photons there. It's teleportation with no energy exchange at all, except for the photons themselves which leave just as they entered. (It's magic, after all).

Since their only function (from what I see above) is that they connect to another mirror by means of a unique name, I don't see any need for a limit on known languages. Whoever makes the mirror can specify a key-phrase and a name. When you want to connect to some other mirror, you say the key-phrase for this mirror verbatim, and then you say the name of the target mirror.

If the magic were a little more sciencey, (and I'm "bending" the rules here hehe), then a limitation could include that the means by which the magic mirrors transmit this light is by bending the causality-axis of the observable universe around a [pick your number > 5]th dimensional axes, so that it contacts itself immediately at the point of the two communicating mirrors. The issue here is negligible at first, but if you use very big mirrors, or thousands of them at once, then small gravitational and causal distortions begin to appear in high-mirror-traffic areas, affecting the speed of light in those locations. Now, bear in mind, mirror-traffic occurs along a string, if you will, which doesn't move straight in the 3rd dimension, but may affect the speed of causality in some mathematically predictable location relative to the mirror. Furthermore, the distortions don't necessarily have to happen at the same time as when all the mirrors are in use, and the distance in space/time between the heavy mirror-use and the distortion may vary based on the physical locations of the mirrors in question.

Since matter can't be passed through the mirror, but only light (and light-like stuff), magnetic forces may variably traverse the mirrors as well. This can be explained by means of a sort of filtering substance which is built into the mirror at design-time. The substance doesn't have to be a magical element, but could be a common element arranged in a very specific pattern so that it stops normal matter but allows waves to pass through it (like the way that the holes on the front of your microwave are just the right size to stop microwaves).

The energy required to perform this could actually be stored in the substances comprising the mirror, and could be such that it is only released over a very very long period of time. We are so used to getting tiny bits of energy out of gasoline that we tend to forget the unimaginable potential stored in every single atom around us. Suppose you vibrate one of those atoms in just the right way, by saying the magic words to it perhaps.... and the magic mirror all comes together.

So, what this looks like in practice is (in a very minor case), a bunch of people are using mirrors together, and then one of them is 10 minutes late to a meeting, another one feels like everything is very heavy (and everything is indeed a few pounds heavier) for a short time, and maybe another one loses his keys and finds them in a strange place. These kinds of small mishaps tend to happen inexplicably at first, granting the illusion that heavy use of these mirrors is bad luck in a sort of small way. Much later on, scientists measuring gravity and trying to understand the universe can begin to develop formulae around the specific behavior of the mirrors.

So then the recipe for the mirror has to include at least two parts in addition to the regular mirror stuff: a magical pattern impressed on some substance, for stopping normal matter but passing waves through it; and a substance which is picked apart by the forces of the universe for the duration of the mirror's life (maybe a few hundred thousand years if the mirror isn't broken).

I hope this helps!

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    $\begingroup$ Looking back at this answer... it might make mirrors even more OP... suppose scientists get really good at predicting where temporal distortions will occur, and start making mirrors with intent to slow time in different parts of the world. Pretty scary stuff. $\endgroup$ – boxcartenant Oct 9 '18 at 21:48
  • $\begingroup$ Does light entering a mirror at sea level and exiting it's companion in a 16,000 foot elevation Tibetan lamasary get red shifted. And the converse? If not, how is energy conserved? $\endgroup$ – Sherwood Botsford Feb 4 at 14:07
  • $\begingroup$ @SherwoodBotsford Good point! We wouldn't want to lose potential energy without converting it. I think that (if we were to explain that away then) the key would have to be in explaining that release of stored energy can occur along uncommon spacial axes (like the good old 4th dimension in Abbott's Flatland), and so the energy in the observable universe would be changed, but the actual sum of energy in the universe (observable + not observable) would be unaffected. Maybe it eventually comes back around as those disturbances in space/time, speeding or slowing time to make up for the change. $\endgroup$ – boxcartenant Feb 5 at 21:23
  • $\begingroup$ But whatever the conversion is, must be reversible. Conversion to/from darkmatter? Note: difference in energy is small. A frequency shift wouldn't be visible in any vertical distance obtainable on Earth. $\endgroup$ – Sherwood Botsford Feb 6 at 22:18

Magic mirrors link to their maker’s life force, effectively stealing usable calories from the person that produced them in order to pay whatever energy cost they incur. When a mirror is in use a person must eat additional food to compensate, and if there are too many mirrors they’ll starve to death as their metabolism fails to keep up. The same is a problem for peak usage: sudden withdrawal of energy could lead to hypoglycaemia or even shock.

Needless to say, when a maker dies their mirrors become regular old mirrors with fancy names engraved in the frame. That’s a big enough flaw in and of itself for many applications of the mirrors, but coupled with the increased dietary requirements it becomes quite crippling.

This flaw might not make itself immediately obvious, leading to the first mirror manufacturers to die seemingly impossible deaths. With a suitable worker scheme (and a big canteen) it may be possible to mass produce mirrors, or push the final step of mirror making onto the consumer (linking it to them instead)

It also nicely ties in with the image of the skinny wizard, though I’m pretty sure Merlin wasn’t carrying round glucose pouches in case a long distance call came to collect.

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    $\begingroup$ And then the mirrors find a new use as the 'miracle machine' for the weight loss industry. $\endgroup$ – Skyler Oct 10 '18 at 19:21
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    $\begingroup$ @Skyler: Want to get slim and put your body under unpredictable occult strain? Come work at Morgana’s Miracle Mirror Machine and watch the pounds burn away! $\endgroup$ – Joe Bloggs Oct 10 '18 at 20:07
  • $\begingroup$ @skyler Methinks this is a first non-US only answer, it won't apply due to a lack of absorbed calories and potion size in other places being smaller. $\endgroup$ – theREALyumdub Oct 10 '18 at 21:39
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    $\begingroup$ But Baba Yaga is already dead long ago (if I remember those legend correctly), so her mirror should not work at all, when found. $\endgroup$ – gilhad Oct 11 '18 at 1:06
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    $\begingroup$ @gilhad Or is she??!? $\endgroup$ – Joe Bloggs Oct 11 '18 at 5:40

Many answers highlight the potential for providing solar power- a mirror in orbit could shine light onto a solar panel, bypassing the light-scattering atmosphere and providing 24-7 sunlight. My answer also points out how the mirror can be used as a weapon that can shoot lasers, gamma rays, and x-rays.

If you want to limit these uses, which revolutionize alternative energy and war respectively, block all but visible light from passing through the mirror. That lowers the effectiveness of using mirrors for solar, because you cannot capture UV waves. Shining nonvisible light at the mirror will cause it to bounce off, reflecting whatever nasty waves you are shooting at it back at you.

You may be wondering how the mirror blocks lasers, which are concentrated light. The mirror absorbs a very small amount of light as it passes through and emits it as heat, like a normal piece of glass. When a laser shines on the mirror, the heat captured is much greater because of the laser's concentration. You end up burning a hole in the mirror, so only low-intensity lasers can be used.

Another answer suggested that mineature lasers could somehow be used in computers and fiber optics. Well, Pavel J. didn't notice that at random, some of the light shining through was refracted while entering and exiting the mirror, coming out at a different place on the mirror right next to where it should have been. Some light was absorbed by the mirror. Just a photon at a time, but in computers, where communication errors are a big deal, this will be a big problem. To combat transmission errors, computers will use increased parity. Make the error frequency high enough, as in several missing or moved photons per mirror per second, and the parity bits required are no longer worth the benefit of having almost zero infastructure.

Another benefit of these mirrors is their ability to pass through solid materials at the speed of light in a vacuum. However, if the light can't pass through opaque objects, and instead takes the path of least resistance like electricity does, it will be much slower. Going around the planet would be slower than going over it. Another consideration is that the light will pass through transparent materials if all other possible paths provide more total resistance, so local and faraway conditions like fog, buildings, and storms can all introduce a delay and degrade the signal, in the same way that WIFI is dampened by obstacles. This provides an explanation for why the photons are sometimes missing or moved (refraction from water droplets or vapor) and why some light is absorbed (but not emitted by the mirror in this case). That is definitely not something that a simple test in good weather at a short distance would pick up on.

Given all of these obstacles, the mirror would not be a life changing discovery, and while communication would be a major benefit, its uses would be severely limited.

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    $\begingroup$ Re: data loss: packet loss is normal in wireless communication and 10% loss is well within the acceptable range. Given the advantages magic mirrors offer, even 50% loss in a 2-way connection could be an acceptable trade off for those advantages. $\endgroup$ – Martin Carney Oct 9 '18 at 21:40
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    $\begingroup$ @Martin In my last paragraph I explained that the errors could be caused by weather patterns, making the amount of error random. The error frequency could actually be very high without people noticing. Even if all pixels are moved a little, the eye won't be sensitive enough to tell, but a computer will. $\endgroup$ – John Locke Oct 9 '18 at 23:14
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    $\begingroup$ @JohnLocke spatially coherent random displacement can be compensated by transmitting a registration pattern at all times. In other words, just flash QR codes really fast. If a person can read it, so can a computer. Even high level of nonlinear displacement should be possible to compensate with enough AI - edges in QR codes can be used to register them onto a grid - or you can even devise a protocol that is unsusceptible to deformation. $\endgroup$ – John Dvorak Oct 10 '18 at 19:55
  • $\begingroup$ @John Still, the amount of infastructure for one continuous length of fiber-optics is cheaper than a bunch going a relatively short distance, hooked up to cameras and monitors running software to continually encode and decode QR codes, which means lots of maintenance. The QR codes will be a bottleneck for speed, because they can't send as much information as a fiber optic bundle of the same size... $\endgroup$ – John Locke Oct 10 '18 at 23:00
  • $\begingroup$ ...Normally, there is one fiber optic bundle running down the street that branches off into homes. You can hook up to the houses with mirrors and QR protocol to the fiber optic cable down the street, but the total cost including repositioning the mirrors, cleaning the cameras, and powering both computers will be much higher than just branching from the nearby cable. $\endgroup$ – John Locke Oct 10 '18 at 23:00

These mirrors don't display the video on their surface or produce the sound. Instead they directly tap into the Visual and Audio Cortex of their user's brain to produce vivid images in their brain.

The actual data delivered to the brain was vivid and incomplete. Our brain is error-correcting and fills in the missing gaps to trick us into seeing a more realistic video and audio. But, it's slightly draining on the brain-power and people who used it for several hours and on a regular basis reported experiencing fatigue and headaches in some people.

A team of scientists tried to open-up a few mirrors and try to find out how they worked. These mirrors transmitted in the long-range Radio frequencies in the kilo-hertz range and had very low bandwidths of less than 100 kilo-bytes at max, similar to the AM radios of the olden days. But, nobody has any clue about how it influences the brain and tricks people into seeing and hearing stuff. A video camera recording the mirror while people are communicating, only sees a usual mirror with the usual reflection of the room and the camera.

They predict that it might be using brain waves or some such. But nobody knows how to prove any of this speculation.


A minor limitation, but one that impacts the "first law of Thermodynamics" request (and prevents photon duplication): The product of Intensity and Surface Area is constant between mirrors.

This means an picture going "in" to a 1'sq mirror and "out" of a 2'sq mirror will be half as bright on the other end, and the return image will be twice as bright as it originated. Similarly, a sound will be louder/quieter along the same rules.

This means that pairing a tiny mirror with a large mirror functions almost exactly like a lens-based microscope does, or that a large mirror facing out paired to a small mirror pointing at a CCD or CMOS chip will act as a "Night Vision" camera.

Facing a paired large mirror and small mirror at each other will just focus the light/sound down ever increasing cones until you get a laser-like "maximum density" (or diffuse it the other way). Of course, with a light source behind the small mirror, you can keep pumping more and more light into the loop (maintained at 100% efficiency) until you have yourself a death-ray by "dialling" a different mirror from the large one...

  • $\begingroup$ This isn't a limitation; quite the opposite, in fact! This would make it possible for me to, in my own home, build a portable superweapon (have a drone carry a mirror). $\endgroup$ – wizzwizz4 Oct 12 '18 at 18:49


Basically, if you use the mirrors too much, they become less reliable.

  1. The magic mirrors rely on the usage of a twisted parallel universe where distance is hugely compressed - 1500 of our kilometers is equivalent to a nanometer in the parallel universe. Quite frankly, our instruments aren't sophisticated enough to detect the difference between the time required for transition.
  2. Magic mirrors actually strip off about .0001% of the energy from transitioning things. Most of this energy is used to power the universe connection, but some additional quantity is radiated into the parallel universe.
  3. Although the parallel universe can dissipate energy quite rapidly, it turns out that releasing too much energy too rapidly in an area with a radius of fewer than 5 nanometers can have strange results.
  4. There is a threshold rate of energy bleedoff where the free energy in the parallel universe's overlapping section will build up and exceed the incoming energy pressure from the mirrors, leading to... interesting reactions. Transitions can be lost as they bounce out at the wrong angle to reality, highly exotic forms of super-high energy matter can materialize in our universe, or transmissions can be misrouted.


Spawn demons (not really demons)

  1. This twisted parallel universe possesses numerous hyper-beings, creatures of such size that even with the differences in scale, they equate to a few meters in our universe. They are, by our standards, malicious
  2. Every mirror transition bears a small risk of accidentally slicing off a small (in our universe) portion of one of these beings and dragging it into our universe. The slice in our universe would be unlikely to be larger than a pea at the time of transition.
  3. These slices, if not destroyed, can function as buds, gathering energy and resources until they can morph into a juvenile version of their spawning entity. Their methods of gathering energy and resources are going to be... unpleasant to residents of our universe.
  4. The chance of this happening is astronomically low - we're talking 1 in a billion. You would never figure this out by basic experimentation.
  • $\begingroup$ Not sure if I'm misunderstanding. Magic mirrors transmit visual and auditory communication but not physical objects. Are you picturing physical objects being passed from one mirror to another as if they were portals? $\endgroup$ – Martin Carney Oct 9 '18 at 21:26
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    $\begingroup$ #4 of energy saturation says a distance of fewer than 5 nanometers. In that universe, it wouldn't be nanometers, it would be merters or km, because when you pass the ruler through, it shrinks along with everything else. $\endgroup$ – John Locke Oct 9 '18 at 21:37
  • $\begingroup$ @MartinCarney energy is matter and vice-versa. $\endgroup$ – Jeutnarg Oct 10 '18 at 14:19
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    $\begingroup$ @JohnLocke the magic mirrors pull things through at the same size relative to our universe - otherwise the twisted distance wouldn't actually speed things up. $\endgroup$ – Jeutnarg Oct 10 '18 at 14:31
  • $\begingroup$ @Jeutnarg Oops, I missed that, my bad. $\endgroup$ – John Locke Oct 10 '18 at 16:04

These mirrors require no power to operate, but they require bandwith. They conduct audio and video troughh the aether.

The more mirrors that are in close vicinity to one another, the more noise there is in the aether - much like having a lot of modern wifi access points operating on the same channel close to one another. Transmission gets slower - voice and video become choppy at best.

The guy who discovered how to make mirrors didn't find out at first because he never tried to transmit while in a 30-story building with 15 mirrors per floor. Once you get a lot of these close together, they start failing. So if you wish to use a mirror efficiently, you have to live to a farm, mountaintop or a desert. People in the cities just don't care about the mirrors anyway since smartphones are more efficient when there are lots of magic mirrors around.


Anyone could be watching. If i understand the mirror correctly, then anyone could say your name and find you at any time. This may not be desireable. Any measures people take to avoid being watched would also impact the usefulness of the mirrors, meaning it would be difficult to reach the ones you seek. I think that between the creepyness of being watched at any moment, and how useless the mirrors would be if everyone blocked them, there is plenty of drawbacks.


1) Size: these mirrors can only be made in hand-held size. Anything larger requires exponentially more energy input while creating them, or the glass of the mirror needs to be thicker until it becomes infeasible, etc.

2) Magic: these mirrors were made by people using magic; maybe they can only be used by people who can use magic. Pavel was lucky that he actually can use magic, but he belongs to the <1% of humanity who has the ability encoded in their genes.

3) Connection issues: it's not a coincidence there were originally only two mirrors: there is nothing in the magic that binds two of these together; they simply find the nearest magic mirror and connect to it. Or, alternatively, all of the magic mirrors within a range are connected at the same time.


Magic Mirrors might have been a threat to technological civilization as recently as 10 years ago, but not now.

Problem is, they are obsolete point-to-point devices with analogous protocol. By contrast, most users today are utilizing their personal communication devices for connection with digital services like Facebook and texting. Magic mirrors may beat smartphones on price, but they won't be able to provide nearly the same level of functionality.

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    $\begingroup$ More likely magic mirrod will be components of smart devices. $\endgroup$ – Renan Oct 10 '18 at 1:08
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    $\begingroup$ Did you mean analogue? Analogous means ‘comparable to’. $\endgroup$ – Joe Bloggs Oct 10 '18 at 5:51
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    $\begingroup$ This answer feels like you read neither the previous question, nor this one... $\endgroup$ – Daniel B Oct 10 '18 at 7:26
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    $\begingroup$ @Renan "$50 of materials" - 4G LTE modem for a smartphone cost a small fraction of that. The mirrors may, however, supplant modern internet backbone. $\endgroup$ – Alexander Oct 10 '18 at 7:36
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    $\begingroup$ "50 of materials" when built by hand, by a layman, at the same size as the original. The same layman built their second for $30 and in half the time, still by hand. Once a manufacturing base was up the cost per unit would be comparable to a 4G LTE modem chip. $\endgroup$ – Patrick Oct 10 '18 at 11:25

Each Mirror Requires a Unique ID

Unfortunately these ID's have a limit on size. So eventually there will be more mirrors than ID's and they don't connect to each other but interfere with other valid connections causing the 2 working mirrors to stop functioning as intended. It would not be immediately noticeable and any mirrors currently owned and used could stop working causing customer complaints and even lawsuits.

  • $\begingroup$ By "limit on size", do you mean "only x number of IDs can exist at a time", or "each ID can only be up to x in length"? Because if the latter - the existing examples are "Creator's Name, then 2 words". There are over 170,000 words in the Oxford Dictionary - if we discount half of these as "unsuitable", that's still over 7 billion combinations per creator. $\endgroup$ – Chronocidal Oct 10 '18 at 22:57
  • $\begingroup$ @Chronocidal each ID can only be up to X in length and cuts off the rest of the characters $\endgroup$ – Reed Oct 11 '18 at 13:30
  • $\begingroup$ I was going to post something similar. Instead of IDs I would just say there are a limit of bands the mirrors communicate on. By default they discover a free band, but once they are full you will just ease drop on someone else $\endgroup$ – Andrey Feb 4 at 19:49

The problems

Some of the ways in which the mirrors are overpowered based on the previous answers are:

  • As a computer component for long distance data transfer they blow current technology out of the water, with their light speed, degradation free transfer of data.

  • data transfer is totally secure

  • they have no interferance

  • As a method of energy transfer they are overpowered, capable of transferring unbounded amounts of energy at lightspeed without loss

  • They may be able to break the laws of thermodynamics by creating energy (if a small mirror is paired with a larger mirror, and this mirror produces an image of the same intensity as if it were there, then the number of photons being emitted by the larger mirror would be greater than the number hitting the smaller mirror)

In short

The key problem with these mirrors is that they are too perfect; adding lots of minor limitations to all the areas where they seem to be perfect will be a more subtle way to make them less overpowered than adding a single major flaw. It will also be more robust, as a range of minor limitations will be less likely to break physics in new ways, or to be subject to easy work arounds.

Suggested solutions

  • Firstly, make the transfer of data slightly less than lightspeed, and variable depending on location. (But close enough to lightspeed that Pavel's physics geek friend who set up a simple experiment to check it could not detect the difference). This gives a little leeway, allowing for a mechanism for the transfer which does not break physics as we know it. It also makes this tech more equivalent to fibre-optics and satellite communication.

  • Secondly make the product of Intensity and Surface Area constant between mirrors as explained by Chronocidal. This avoids breaking the first law of thermodynamics.

  • Add some subtle signal degradation. For example you could have a brightness factor which decreases over distance, such that $r = ic^d $ where $r$ is the total light output of the receiving mirror, $i$ is the total light hitting the input mirror, $d$ is a measure of distance, and $c$ is a constant less than 1.

  • Add some interference - when lots of mirrors are used close together they are all cloudy and unclear, or have random flashes and sparks flying across the screen.

  • limit the amount of energy they can transfer - perhaps it is possible to make them more robust to deal with high intensity energy - but increasing the current upper bounds will be a slow process of research.

  • limit the minimum size of these mirrors (at least without ongoing research), making them less useful as computer components (this is realistic as the original creators would never have conceived of people wanting really tiny versions of the mirrors).

The result

If these limitations were added the mirrors would still be revolutionary new components for computers and be used in ingenious ways, but they would not be quite so overpowered as to totally change computing. They would also be less likely to break physics as we know it.

As two way face-to face communications devices and visual links on earth, these limits could be calibrated to be hardly noticeable.

A note on security

Without knowing how these devices connect I believe any serious cyber-security expert would be extremely dubious about using them for secure communications - since this would be essentially security by obscurity. Who knows if someone has a copy of Baba Yaga's lesser known work "Intercepting Magical Communications"?

Secure signals over magical mirrors would need to be encrypted. Thus I don't think we need to add any artificial limits to their security of connection, other than doubt.

  • 1
    $\begingroup$ The concern about breaking the First Law of Thermodynamics is a bit overblown, I think. What you need to worry about isn't getting "free" energy per se, it's being able to loop your energy generation so that you can get exponentially increasing amounts. I would note that most of the time, when people think they're not creating energy, they actually are (have you considered how gravitational fields come into play, for instance?) $\endgroup$ – Obie 2.0 Oct 12 '18 at 5:35

The mirrors don't actually transmit light or sound

Instead the mirrors provide a psychic illusion which is, to a living creature, indistinguishable from a transmission of light and sound. But it cannot be used to transfer energy or provide communication between mechanical components.


I think they only appear perfect, but they are still magic transceivers. They transmit through the magic domain to the receiver, but diffraction and side lobes still apply. Larger mirrors work better than smaller ones, but every mirror in service contributes magic noise to every other receiver. They fill with smoke until the magic tunes properly. The ever growing number of mirrors, especially the convenient, portable, smaller mirrors, the higher is the noise floor. The smoke doesn't clear quickly, and eventually not completely. Communication degrades as the magic splatter interferes with the magic by intention. Soon, reliable communication requires larger mirrors, which uses more of the magic ingredients.


In a response to the monetize post, found here, it is stated:

If it handles sufficient intensity then a mismatch in sizes makes some interesting industrial processes possible. (May have some problems with the laws of thermodynamics, but hey, this is magic, right?) Consider a 2 meter mirror connected to a 1 mm mirror. Put the big one outside. Now you have about 4 kW coming out of a hole 1 mm in diameter.

To prevent breaking laws of thermodynamics, what if the mirrors could only connect to other mirrors of their own size? This way you aren't allowed to compress the energy. Also, in response to your point,

can't be misused by a mad scientist to easily destroy the world (eg duplicating photons in a loop to instantly create massive amounts of energy from nothing).

being limited to connecting to only one mirror at a time would also prevent duplicating photons.


Mirrors are immobile

A mirror needs to be grounded to dissipate excess magic harmlessly. This grounding effect is invoked when the mirror is ritually placed where it belongs, at which point it cannot be moved more than a couple meters from the original location on Earth it was placed. this means you can't use it for mobile communication or launch it into space, and you need someone familiar with the grounding ritual to install it.

  • $\begingroup$ This is a good suggestion, but it's something that Pavel would have noticed when testing the effects of distance between mirrors. $\endgroup$ – Martin Carney Oct 11 '18 at 13:18
  • $\begingroup$ @MartinCarney That doesn't mean it can't be a good limitation. You can play around a bit with what exactly causes a mirror to be grounded and ways around that. Maybe it needs to have a direct connection to the ground to be grounded, possibly through a wall. So you can still move it around after it's grounded, but you can't have it on a mobile phone, in a ship or in orbit because to use it you need to reground it. $\endgroup$ – Nzall Oct 11 '18 at 13:24
  1. The mirrors connect to the nearest mirror with the requested key, regardless of which alternate reality it is in given some distance metric.

    • For the most part this could easily go unnoticed, after all the difference of a decayed particle 2 * 10 ^ 30 lightyears away does not have a great affect on things happening on earth. But occasionally two mirrors connect and transfer the wrong information. Or a mirror refuses to connect, because already connected.
  2. The mirrors derive their energy from a simple void energy reduction, this increases the amount of Dark Matter, increasing gravity. The effect is negligible with a handful of mirrors, but the demands for billions of mirrors in use for modern telecommunications is quickly increasing Earths gravity.

  3. The mirrors used an ingredients that original came to $50. Unfortunately there is no known way to recycle the mirrors, and the supply of this particular ingredient is non-renewable. Prices soar, only the wealthy own a mirror.

  4. The mirrors are all quantum entangled with each other. While a connection does indeed occur between just two mirrors, the strain is spread across them.

    • due to increased production, mirrors are feasible indestructible. The latest methods of throwing them into a star results in melting every mirror in existence.
    • due to increased production, each mirror made is making every mirror progressively more brittle. A single person dropping their mirror results in many thousands of mirrors cracking.
  5. The mirrors are actually part of an experiment being conducted by n dimensional beings. The mirrors in fact do nothing, but the n-dimensional beings are moving the data back and forth themselves. However this is an experiment so they are not faithfully replicating all data. The intent of this experiment is not actually known.

  6. The mirrors are slowly becoming dark, the cause is unknown. It does not appear to have anything to do with their construction. Its almost like the source of their power is dwindling. Certain parts of the planet are still capable of powering them, but their are growing dead-zones.

  7. The mirrors are slowly twisting space time. Every time two mirrors connect they are sowing two disconnected places together. When the mirrors are moved the seam still exists.

    • the seam forms a scar, the longer it is used the rougher that piece of space time. A person might walk through such a spot and have their heart appear twenty thousand miles away.
    • light starts leaking through places where mirrors have been in continual use and then removed, like two super imposed images.
    • These seams might store the anti-energy generated through use of the mirror, when it collapses and annihilates it causes a huge explosion. The amount is relatively stable in small amounts or during infrequent test, slowly releasing. But the frequent widespread use in dense areas, or the amounts produced by industrial 8metre mirrors can become unstable and quickly release.

On top of needing the name of the mirror you wish to connect to, you must also align the mirrors to some reasonable degree of accuracy. The physics-y answer is the mirror is acting like a portal letting the photons through, but the caveat is the photons must still travel in the same direction as they did before (consevre momentum), thus the mirrors must be pointing towards each other. Over long distances it gets harder to point them at each other, so they become less useful for individuals looking for long distance communication. Large organizations however build large central hubs with mirrors pointing to other hubs. You could then have normal mirrors reflecting the light to other magical mirrors (to get round the pointing at each other issue) and thus you build up a series communication hubs with point-to-point magical mirrors,which might then go to smaller hubs before eventually reaching the destination. You'll need a small army of people to change the pointing of non-magical mirrors route your message to the right magical mirror, much like telephone operators in the past.


This is magic. Magic always has a price on the wielder.

The mirror uses energy of the invoker. It takes 1 calorie/minute per square inch of both mirrors. So a pair of 2x2" mirrors have 8 square inches. 1440 minutes per day. It takes 12,000 calories per day to keep it running. This is doable. Pre-chainsaw, a lumberjack would eat 6-8 thousand calories per day. Similar to what a teenage male in a growth spurt eats.

A bathroom medicine size mirror at 16 x 25 inches linked to a tiny spy mirror takes 400cal/minute to use. By comparison basal metabolism is about 1 cal/minute. Using this mirror would be close to instantly fatal, depending on the mechanism it harvests energy.

Adjust the 1 cal/minute for your story.

Perhaps the energy used is proportional not to the area but the largest linear dimension. This makes larger mirrors easier to deal with.

Or perhaps to the distance between the mirrors. If it was proportional to a power of the distance, then you have an interesting control mechanism:

Victim is forced to link two mirrors. I take the two mirrors. As long as he behaves, I keep them in the same drawer. If he mis-behaves, I put one on a freighter going to Australia.

With analogy to black mail, this is silvermail.

We institute a new title: "The conscience of the King" On ascension to the throne, the king invokes a pair of mirrors. These are put in the charge of an Abbot at monastery near the capital. The abbot can't tell the king what to do, but can let the king know when he doesn't approve.


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