I've done a bit of research on various materials that can absorb light, like Vanta Black, some paints and so on. My question is, could this material protect someone from Night Vision Goggles seeing as they use light to see in the dark?
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20$\begingroup$ Main issue with materials like this is that the user would look like a dark silhouette against almost-dark background. The same reason why deep blue, dark green or grey is better camouflage than black for most night environments. Generally you want to look like a part of your surrounding, no matter how dark it is. $\endgroup$– byMaelstromerCommented 2 days ago
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5$\begingroup$ Some night vision devices work vith visible light; they operate like very sensitive photo cameras. Some work with visible light plus near infrared light. Some work with thermal infrared radiation. $\endgroup$– AlexPCommented 2 days ago
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$\begingroup$ @AlexP Ahh ok, so there's a spectrum for what they all look for then. Interesting 🤔 so there'd need to be more layers of shielding and protection from verious forms of enhanced vision. $\endgroup$– AltariousCommented 2 days ago
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1$\begingroup$ This is a great idea, but let's look at the limitations of the real thing (like Vanta Black). The test is 99.5% of the visible spectrum, not 99.5% of all light. Light be photons. Radio waves be photons. Gamma rays be photons. And as Nosajimiki pointed out, the IR spectrum be photons. But should that stop you? A worldbuilding substance similar in concept to Vanta Black that could actually absorb 99.5% of all photons would definitely protect someone from night vision. And radar. And lasers. It would be close to the perfect nighttime stealth material. $\endgroup$– JBHCommented 2 days ago
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4$\begingroup$ @JBH the IR spectrum would remain complicated. Just because you absorb 99.5% of IR does not keep you from emitting it. And if you could somehow stop yourself from emitting or reflecting any EM radiation, then you would overheat very quickly because you'd have no way for your body to dump waste heat. $\endgroup$– NosajimikiCommented 2 days ago
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3 Answers
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No, you would still glow in the IR spectrum
When solid matter absorbs light, it becomes hotter, and anything that holds heat emits blackbody radiation. There are many kinds of Night Vision Systems, but many of them, especially military grade systems, include a long wave IR sensor that is designed to detect blackbody radiation in a temperature range that includes human body heat. In this case, you are not looking at light reflecting off of things so much as the IR radiation put off by how hot it is. So, if you are 98F and your environment is 72F, you will still glow brightly even if you are not reflecting any visible light.
How to hide your IR signature
There are 2 kinds of IR stealth: passive and active.
Passive IR stealth relies on space gapping something between you and the camera. So, if you have some kind of a shield that is opaque in the IR spectrum and the same temperature as your environment and you hold it out in front of yourself, the thermal night vision goggles will detect the 72F surface of the shield and not your 98F body behind it. This can be further improved with IR refractive paint. This paint is not meant to absorb IR light or prevent you from emitting it, it's designed to scatter or reflect it so that you look like a blur or a pattern similar to your environment in Night Vision instead of a geometrically shaped shield or what not which makes you even harder to see against your background.
That said, most of the time, you will not have a "shield". What most soldiers use for passive thermal stealth is disruptive camouflage. By covering yourself in a netting material, you will still technically glow but it will break up your outline so much that you no longer look like a person and you can blend into your background.
However, many night vision systems include low-light cameras. These are just highly sensitive traditional or near infrared cameras designed to boost visible light. These don't work as well in true darkness as thermal cameras, but they can be harder to fool because they often produce clearer images. For this, traditional camouflage works better. Instead of just trying to put on a plain black suit, visual camouflage uses a pattern of colors that look like your local environment and break up your shape.
If you want the best of both worlds, you can wear a Ghillie suit. This will break up your silhouette in both the visible light and IR spectrum. Some Ghillie suits like ATGS-17 also even include IR refracting technology.
Active IR stealth is used mostly on armored vehicles that can't effectively space gap themselves. This is basically an A/C system built into the outer layer of armor. Not only can this match the environment, but it can selectively heat and cool plates to create IR patterns to change what you look like; so, you can make a tank look like a car or a line of trees, etc.
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$\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$– L.Dutch ♦Commented 3 hours ago
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Night visors amplify infrared and/or visible light. If your super black coating doesn't block all those frequencies, the coating would not work against it.
Additionally, if it worked egregiously, you would have another problem: the background against which your masked object stands will not be masked, so, quite paradoxically, it will stand out more. Think of wearing a black coat at night on a dark road or wearing the same dark coat on a snowy surface: where would you be more noticeable?
If you want to not be seen, you have to blend with the background.
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$\begingroup$ You know I just read up on one of these materials that can actually block Infrared Light. But I'm assuming that still wouldn't get rid of the object standing out due to the background. Would active camouflage like bending light or something more realistic like the Chinese Camera Suit work for getting rid of that problem? $\endgroup$ Commented 2 days ago
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Black? That how we describe something that readile absorbs light, but in thermodynamics it also describes something that emits light when hot.
Black in the thermal infa-red would mean you glow in that spectrum.
So, no you'd be better off using the opposite, mirrors.
Mirrors show a reflection of the surroundings; what better way to blend in?
This is especially true at night when there are no shadows or accidental reflections of the Sun.
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$\begingroup$ umm.... the 'black' in blackbody doesn't refer to the color of the thing that emits, rather it refers to the fact that even when something is black, it still emits. In other words, everything emits blackbody radiation, it's just that black objects only emit blackbody radiation without all that other reflected [presumably] visible light. $\endgroup$ Commented 14 hours ago
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$\begingroup$ untrue. highly reflective things emit proportionltely less black body radiaton. hence "furnace" in the definition. $\endgroup$– JasenCommented 14 hours ago
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$\begingroup$ Do you have a citation for this claim? The reality is that emissivity is independent of color. $\endgroup$ Commented 3 hours ago