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OK, OK, I know, darkness is nothing but absence of light, so there can be no substantial darkness. Darkness, on its own, doesn't exist.

But, can we not get pretty close to this?

Can there be something - I don't know what, smoke, gas, clouds, fog, atmosphere, dark matter, whatever - that could be ubiquitous in the atmosphere in large areas, spanning whole cities or, in extreme cases, even whole countries, that would have the following properties:

  • It would absorb light, therefore darkening areas it would affect. That it would be dark around would be its only visible trait.
    • In places where this something would be moderately concentrated, bright day would present itself about as a night with a full moon - so while people could go around with a naked eye, they would have to use lamps to read; more severe concentrations would mean that even during a bright day strong reflectors would have to be used to not bump at the wall; in extreme cases no practically feasible amounts of natural or artificial light would help and people would simply see nothing.
    • This differs this mysterious substance from stuff like smoke or fog; while both obstruct vision, both do this in a different way than simply reducing the amount of ambient light and are visible on their own.
  • It would otherwise not be detectable in obvious ways. It would have no smell, it would not obstruct movement, it would not make people breathing it in ill, etc etc.
  • It would be ubiquitous, reaching wherever air would reach. So air purifiers wouldn't help. Nor would help shutting oneself in a cellar or a bunker, unless this cellar or bunker had no air supply. However, shutting oneself in an extremely air-tight room and scientifically synthesising air somehow would help.

Can such a substance exist? What would it be like? Could a Dark Lord realistically summon such a substance without having to resort to supernatural explanations?

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  • $\begingroup$ It is a very cool idea and good stuff for a story. I think the supernatural works the best. I cannot think of a way to make physics do this. There is a scene in the movie Constantine that is sort of like what you describe: youtube.com/watch?v=O1fDNFA6Ozk $\endgroup$ – Willk May 8 at 17:44
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    $\begingroup$ Sounds like a story where a cargo plane full of Vantablack exploded above the ground. $\endgroup$ – kikirex May 8 at 17:49
  • $\begingroup$ When does this occur? Is modern science available to the people affected? $\endgroup$ – chasly from UK May 8 at 17:56
  • $\begingroup$ It is so weird to see a positively-scored question with six answers and not one of them with a single vote, up or down. $\endgroup$ – JBH May 8 at 23:01
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Have you ever heard of the sound suppression system used in some headsets? It works by creating a sound wave with the same amplitude and frequency of the sound you want to suppress, but just with the opposite phase.

In this way the interference between the two waves causes silence.

The same principle can be used for your darkness: electromagnetic waves with the same intensity and frequency of the electromagnetic waves you want neutralized, on opposite phase.

interference pattern

Just shift the phase a bit, and the zeroing will not be perfect, leaving some light visible.

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  • $\begingroup$ Wouldn't that cause complete "whiteness"? $\endgroup$ – Soan May 8 at 18:42
  • $\begingroup$ @Soan, no, not at all $\endgroup$ – L.Dutch - Reinstate Monica May 8 at 18:49
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    $\begingroup$ I’m relatively certain that this doesn’t work because there’s no way to generate an ‘out of phase’ E.M. wave that will actually interact destructively. If pressed for further explanation I’ll probably mumble something about baryons and quantum mechanics, but then again I haven’t had much sleep of late, so maybe it does work.... $\endgroup$ – Joe Bloggs May 8 at 22:37
  • $\begingroup$ I have broken the non-voting streak! Electromagnetic destructive interference can be created, it's just a pain in the neck and normally isn't an issue because heretofore it's only value would be to jam radio signals and there are much simpler ways of doing that. The problem with destructive interference is that it doesn't blanket anything. It's only effective in narrow areas. But I love the idea, it would be a great way to rationalize the narrative effect. $\endgroup$ – JBH May 8 at 23:58
  • $\begingroup$ @L.Dutch This sounds like a theory that could work, but not like an answer to the actual question. To make this "light suppression system" substantial, you could handwave a gas that gets energetically excited by photons and emits photons on opposite phase. (I'm not sure if polarization would make any difference here). This could black out the light directly passing through the cloud of gas and leave only reflected light visible to humans. $\endgroup$ – Elmy May 9 at 7:30
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Disclaimer: I misunderstood aspects of the question, so this might not be the kind of answer the OP is looking for. But I had a tremendous amount of fun writing it, so I'm leaving it up. But! like I explained to Soan, if the Dark Lord had mastered the science of photonic resonance, allowing him to shift normal photons into daniels, it could work! Muahahahahaha!

You might not be thinking about this in the right way

Photons don't "emit" anything. They are the thing "emitted." Our eyes (rods & cones) "detect" this object and our brains interpret that detection.

Which means you're not looking for a particle that "absorbs" light. You're looking for a particle that our eyes detect but our brains refuse to interpret. The result would be darkness.

That distinction, detect but refuse to interpret, is important. Our eyes don't detect x-rays, for example. Which is why X-rays don't cause "light" or "darkness" as far as our brains are concerned.

So, let's create a particle

I can't call it an "antiphoton." Antiphotons already have a connotation/definition in the world of quantum physics, and it isn't as a particle that our eyes can detect but our brains can't interpret. That's truly unfortunate, because "antiphoton" would be the most obvious name for this particle.

So, let's call if "Daniel."

What are Daniel's characteristics?

Daniels have all the same characteristics of photons with one exception, our brains don't know what to do with them. The rods and cones of our eyes think they're photons, but when that data is sent to the brain, it's response is "huh?"

From a scientific standpoint, this would be hard to justify other than by hand waving. Simplistically, rods and cones are little more than frequency-sensitive switches. The impact of a photon turns the switch momentarily on. When the brain is told that a particular switch was turned on, it uses that fact to build an image. In other words, rods and cones are chemically complicated but systemically simple.

In a sense, we're asking the brain to not understand that the switch was turned on. In this case, it would be helpful if someone with more medical knowledge than I could edit my answer and fill in this blank. Is there the equivalent of two data paths from the rods/cones back to the brain? One that indicates the closure of the switch, another that tells the brain what the switch means? If so, then all we're asking the body to do is not send the interpretive data back to the brain. (But, if it's as simple as I think it is, hand waving is all we have left.)

What does this mean if both photons and daniels are present?

Obviously, if all that exists is a room full of daniels, then effected humans are blind as the proverbial bats. Darkness abounds.

But... Let's say that a candle is burning and someone has a bunch of daniel-emitting flashlights who are the polos in your game of visual marco-polo? As you try to find the candle, they're casting the beams of daniels about causing blindness and distraction. Your eyes would be getting a mix of photons and daniels (and your brain might get a splitting headache). In a normal room, the image of the candle would be varying in brightness and occasionally spotty.

Actually, make this a room with mirrors for walls and this game might be really fun.

Conclusion

What you need is a particle having all the basic characteristics of a photon, making it detectable by the rods and cones in our eyes, but is otherwise incomprehensible by our brains — meaning the brain will only interpret the particle as "darkness."

I've lovingly called this particle a daniel.

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  • $\begingroup$ I belive this might help you: youtube.com/watch?v=CoLQF3cfxv0 $\endgroup$ – Soan May 8 at 18:23
  • $\begingroup$ But with your solution you would create a completely dark world where nothing can be seen by nobody. So not even the sun would be visible, and eyes wouldn't exist in the first place. $\endgroup$ – Soan May 8 at 18:26
  • $\begingroup$ @Soan, like I said, "frequency sensitive switches." As for your second comment, that's not true. Photons are not being absorbed. There's simply a lower percentage of them being detected compared to the whole. Can you imagine how many daniels you'd have to emit to reduce the percentage of photons detected by your eyes due to sunlight from 100% to 1%? (answer: 99 suns worth of daniels...). If daniels carry the same thermal potential photons do, you'd burn to a crisp long before you had a chance to experience that kind of darkness. $\endgroup$ – JBH May 8 at 18:28
  • $\begingroup$ @Soan, you know, from that perspective my answer is a bit of a frame challenge. The only simple way to "cause darkness" is to occlude it. On the other hand, if the Dark Lord had mastered the science of photonic resonance, allowing him to shift normal photons into daniels! Muahahahahaha! $\endgroup$ – JBH May 8 at 18:30
  • $\begingroup$ Sorry misunderstood your claim. I thought you meant to replace photons with "daniels". $\endgroup$ – Soan May 8 at 18:39
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The thing that makes fog visible is that the shape of the water droplets causes them to refract light, but a glass of water with a dye in it will reduce light inside it without the water necessarily being "visible" on its own to creatures living inside it.

If you had a dense smoke or extremely sparse liquid, made of a translucent substance like a glass of water, whose particulate was shaped in a way that didn't refract light the way particulate steam does... or maybe like a "dye for air", which wasn't quite visible on its own the way dust is, but which nonetheless absorbed or changed light on the way through it, you could achieve this kind of effect. I don't know about any substance with those properties IRL, but IMO it's conceivable that one could exist.

Also, I'm not 100% sure if I'm right about how this works, but I'm lead to believe that the reason far mountains look blue is because air is blue. Imagine if air was black -- the mountains in the distance would just look darker. Air can't be seen on its own, but sometimes I can see far mountains well, sometimes they're blue, and sometimes they aren't visible at all amidst the blue haze. All you're doing is just reducing the basline render-distance for real-life objects, and changing the color of that haze.

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    $\begingroup$ A semitranslucent black liquid with the same refractive index as air was my initial thought, but it falls foul of the air filters requirement. $\endgroup$ – Joe Bloggs May 8 at 23:32
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Can such a substance exist? Propably not

Whats the problem?

It needs to be in such a small amount that you are still able to breathe but at the same time absorb 99.999% (or more) of sunlight to create moon like circumstances. Even the darkest substance known is not capable of absorbing so much light. That being said there could be a material absorbing even more light.

The problem this unknown substance would face is that it has to absorb 99.999% of light while being spread out in the air like fog and not damage the inhabitants.

What would it be like? Hot

Why?

When a material absorbs light it gets warmer this is not that big of a problem with most materials because they reflect enough back to keep survivable temperatures. (even then the sand in the Sahara can reach 70°C. Problem is when that’s not the case it can get even hotter. So during the day nobody would leave the house except when there are enough clouds around.

Can a Dark Lord realistically summon it? Maybe

Depending on how this material is created it could be “summoned”. Even if itself couldn’t be summoned it could be moved with wind probably. So If your Dark Lord is sufficiently powerful he should be able to at least let it seems like he can summon it.

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Using our existing physics, I can think of a few ways.

For a start, let us consider what "darkness without obscuring" means.

It means that things in the dark area will look dark, but if you look through it to a light area, they will look light. Like looking under a bridge, the stuff under the bridge is in shadow, everything else is lit.

1) So one way is to have the darkness be at a high altitude, as a canopy over everything. This doesn't work so well, but at a low enough level (10ft or so above the ground) and impenetrable enough, it could work better than clouds. The canopy could be flying insects, nanites, smoke, or some light buoyant film.

2) Other than floating above people's heads, another way is to consider that particles need not have the same dimension at all angles. They could be very flat micro-particles covered in a vantablack-like substance. Their shape permits these particles to fly using the absorbed solar energy, but also means that they mostly block light in one direction.

They'd only need to be further apart than 1 micrometer in order not to block visible light horizontally, and average complete coverage to block vertical light from the sky; that's perfectly doable with super-thin stuff particularly if it's designed to seek sunlight to fly.

These particles would also make flashlights less efficient, since they'd angle towards light sources, but then have to level up as that caused them to fall.

These particles could also make the darkness harmful to flesh, if the thin particles were sharp, like tiny flecks of obsidian; you'd have to venture into the darkness wearing goggles and swaddled in cloth or leather, or risk going blind and being flayed alive by the swirling darkness.

3) But really - what's the EFFECT of darkness? It makes things look dark. So what if it's not in the air, but rather a thin layer over all surfaces? If you tread on the ground, you too become Darkened. You likely don't want that stuff on your eyes, so goggles again recommended.

What the layer is (mites, nanites, slime, dust) doesn't matter, other than that it'd affect the specific way the locals handled the Darkness. Having it be small insects makes it ooky and also explains why carried torches work, if the bugs avoid fire. Depending on the setting, it's reasonable for the reader to believe in insects being controlled as a colony, so sticking together in patches of slowly expanding blackness, etc, and leaving someone who walked out of the blackness.

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We could change the sun to achieve such an effect. If our central star happened to emit light concentrated on a few wave lengths (similar to laser light, also found in some unusual types of stars) and we had a gas which happened to absorb light at those frequencies, we'd get what you want. Ideal would be a gas like argon or xenon, which would have to make up a large part of the atmosphere (more than our 1%) and have some (volcanic) sources. Being a noble gas, it's difficult to isolate, doesn't harm us, doesn't smell, and so on.

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