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Can we create any electrical equipment which works in the opposite way to a bulb, such that is whilst it is switched on all the light in the surrounding area gets absorbed creating darkness?

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    $\begingroup$ Welcome to worldbuilding. I think you should better define what you are looking for: an electrically actuated black curtain can do what you ask, but I suspect it's not in your scope. $\endgroup$ – L.Dutch - Reinstate Monica Jul 26 at 10:42
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    $\begingroup$ I've editted your question to slightly improve the english; hopefully I haven't changed anything else important. Short answer though, "no". $\endgroup$ – Starfish Prime Jul 26 at 10:44
  • $\begingroup$ @StarfishPrime thanx $\endgroup$ – abhilash Jul 26 at 11:04
  • $\begingroup$ FWIW, there are a couple hilarious articles on the subject of "Darkons" written by Bell Labs researchers. Google them for some fun. $\endgroup$ – Carl Witthoft Jul 26 at 14:14
  • $\begingroup$ Welcome abhilash. Please check out our tour and help center. I added the tag light because your question is about removing it, so it seemed appropriate. $\endgroup$ – Cyn says make Monica whole Jul 26 at 14:39
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Maybe possible in theory, but not plausible with any foreseeable technology.

Light is a torrent of electromagnetic waves. Darkness is the absence of any such light waves.

You can cancel out a wave by creating a wave which is exactly identical but with the phase shifted by 180°. This is called "destructive interference". But there are a couple of problems with trying to cancel out a light source in a real-world scenario:

  1. if your two wave emitters (light and "anti-light") are not in exactly the same location, then the interference only works in one spot at a time.

  2. then there is the problem that light is usually not just a wave with one frequency but a combination of multiple waves with lots and lots of different frequencies and amplitudes (that's what defines the color of a light). If you want to cancel out a light source, you need to match all those frequencies.

  3. And then there is the problem that in a regular lighted situation you don't have one light source but many different light sources as well as indirect light. So you don't have the same combination of light waves on every surface.

So you can not just have an anti-lightbulb which you can switch on anywhere and expect to work. You would have to know exactly which micro-meter of surface in the surrounding receives which light frequencies and then send out rays of light with exactly those waves so that they arrive phase-shifted by 180°. This would not just require a tremendous computing power but also the ability to emit billions of unique rays of light with an extremely fine precision.

If you want to prevent people from seeing something, then there are simpler methods.

  • You can obstruct their view with smoke or fog.
  • You can temporarily blind them with a strong flash of light.
  • You can obstruct or disable any sources of light.
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  • $\begingroup$ light and anti-light Note that photons are their own antiparticle, "anti-light" is light. $\endgroup$ – StephenG Jul 26 at 12:30
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    $\begingroup$ Would a black hole work to "suck out" all the photons? I am aware that it would likely have rather catastrophic other side effects but I'm curious if it could still technically leave an area in darkness? $\endgroup$ – VLAZ Jul 26 at 13:16
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    $\begingroup$ @StephenG What I meant with "anti-light" in the answer wasn't a source of "anti-photons", but a light source which sends light waves which cancel out those of other lightsources. I am not sure how I could explain that better. But I am not sure if this is even necesary, because I didn't even mention photons in the answer. $\endgroup$ – Philipp Jul 26 at 13:39
  • $\begingroup$ I'm simply providing some physics clarification. Given the material on WB SE (including my own), I think it's very easy for the lay person reading answers to get confused on these things. You could technically say your source was a source of anti-photons - a photon and an anti-photon are the same thing. :-) $\endgroup$ – StephenG Jul 26 at 13:42
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    $\begingroup$ I feel like this answer severely understates the impossibility of such a device. I think this device would be harder to get working than a device which could un-burn a piece of paper by recapturing all the exact gas, smoke, and ash atoms left over from burning and reassemble them to show you what was written on the paper. $\endgroup$ – Shufflepants Jul 26 at 20:01
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That already exists.

It's called a smoke bomb.

Black smoke bomb

If you stick your head into it the smoke, you won't be able to see s... a thing.

If you make the smoke black, it will absorb visible light in all wavelengths. If you use vantablack, your absortion efficiency goes all the way to 99.96%.

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    $\begingroup$ True, but it also has some potentially undesirable side effects... $\endgroup$ – Carl Witthoft Jul 26 at 14:15
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    $\begingroup$ Ironically you can get a similar effect (blind enemies) with a flashbang $\endgroup$ – jean Jul 26 at 20:24
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    $\begingroup$ Would there even be a discernable difference between creating darkness and a perfectly dark, smooth odorless smoke cloud that didn't dissipate? I guess the difference would be that it would persist after the electricity was removed and would take a perceptible amount of time to expand to it's maximum size. $\endgroup$ – Bill K Jul 26 at 22:16
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Going laterally a bit here.

If all you need for your "darkness" is for people not to be able to see anything, then your device could generate some (unobtanium-based) E-M wave pattern which completely shuts down the optic nerve.
Obviously this will be useless if your intent is to stop hardware such as video cameras from recording information.

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Based on answers above, two options:

  1. High-tech smoke bomb, namely a cloud of nanobots that stay in a given area, fill the air in it evenly, are painted with Super-black paint. In fact, rather than microscopic nanobots, make them more like moths or floating flakes. Device coordinates nanobots and provides energy through induction: nanobots constantly circulate to the device to recharge, and then away from it to dim the furthest corners.

  2. Brute force: device emits super-bright light that makes it impossible to see anything, by overwhelming both retinas in the eyes and sensors in cameras. Device will need a lot of energy, and a very efficient light bulb. Can make it a plot point that it does not last long.

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Although it's counter to every sci-fi show that I've ever seen, wouldn't a shield that blocks lasers also block physical light?

That would make it easy to turn on a shield emitter lightbulb and have it block all the light from entering an area. I'm not sure if it would stop light created in that area.

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