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Can we ever have a black colored (the color of the light and not the body's color) torch that darken (or dis-illuminates) everything? While compared to a normal torch it would function in an opposite manner. If not now, will it be possible to create this in the near future?

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  • $\begingroup$ No, it is only practical feasible to emit photons to illuminate surroundings. In order to dis illuminate something you would need to draw in surrounding photons. I suppose this is theoretically possible with a black hole. If you have a black hole you will not be around for very long, so whatever that does to the illumination is a moot point. $\endgroup$ – Reid Erdwien Mar 12 '14 at 5:21
  • $\begingroup$ A way could be to create a torch which can converts photons of surrounding into massive particles. $\endgroup$ – Anubhav Goel Apr 11 '16 at 2:57
  • $\begingroup$ @ReidErdwien the problem with a black hole would be that it would only dis-illuminate within its event horizon, wouldn't it? $\endgroup$ – tox123 Aug 5 '17 at 0:52
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Black isn't a color. It's just absence of light. So, a torch can't project light having such color.

However, for the second part (dis-illuminate everything), I have an answer: Light is wave and waves can cancel each other. Projecting specially programmed adjustable light wave which create fully destructive interference with other available light waves can achieve your goals. But, the problem is: Full 100% destructive interference isn't possible at this time. You asked for future, so just wait. It may be possible in future.

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  • $\begingroup$ Doing so would have massive 2nd Law of Thermodynamics and Uncertainty Principle problems. To create destructive interference with existing photons, you've have to know their wavefunctions. $\endgroup$ – Acccumulation Apr 19 '18 at 17:32
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Wow that's an interesting question. I believe the answer is no, and the reason is that you can have light, or no light, but you cannot have "not light." If that makes sense. Darkness is the absence of light, so you cannot really have a material darkness.

A similar idea is that cold is just a lack of heat. If you make something cold, it is not because you added cold to it, it is because you took heat away from it. Similarly, you can only add or remove light, you cannot add anti-light.

I'm not sure how to come up with something more sci-fi, you might think about this in terms of anti-photons (if they exist re:this discussion).

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  • $\begingroup$ I am not marking this as an answer (right now) as I want more opinions on this question. Anyways thanks for the feedback. :) $\endgroup$ – Harshal Gajjar Mar 12 '14 at 5:44
  • $\begingroup$ Photon also plays role of antiphoton (when discussing antimatter). When it comes to photon-antiphoton annihilation which is actually photon-photon interaction, interference happens. $\endgroup$ – Schrödinger's Cat Mar 12 '14 at 7:21

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