Comment by WiseWeasel | Hacker News Reader

Comment by WiseWeasel | Hacker News Reader

"The question then becomes, how can it be put to use on Earth, and what benefits could we see on the surface of the planet rather than above it?"

I'm sure there are many applications as an interior coating in optics, such as photography, cinematography, telescopy and microscopy, leading to sharper images. E-Ink displays could use it on the dark side of their "pixels" for higher contrast. Car body paint shops could offer it for the darkest matte black on the block. I could finally have the ultimate set of curtains to ensure cave-like darkness on the brightest day. Ninjas will appreciate it for moving undetected through the shadows (and slightly more commonly with special forces and swat teams, who might also appreciate the coating on their gear). I could get an ultra-black turtleneck to make it look like my disembodied head and hands are animating themselves. My cell phone could be blacker than anyone else's. And finally, this could make for really high-contrast black-light posters.

A lot of those potential applications will hinge pretty heavily on what kind of durability this coating demonstrates. What works great on metal may never give rise to a product suitable for fibers. And what works in space may wear away surprisingly quickly under the constant assault of airborne particulates.

All that said, it does provide a convenient justification for "slightly darker black" turtleneck jokes.

If it is cheap enough, it could be used to easily bypass infrared motion sensors.

I don't think that would work. When it absorbs light, it converts that energy into heat, then re-radiates that heat. That re-radiated heat will show up to the infrared motion sensors.

I see one way you might be able to work around this: if you made a suit out of this stuff, and were somehow able to rig it so that all of the heat is dumped inside the suit, then it would be "invisible" to IR sensors. However, it would get really uncomfortable inside that suit really fast.

Also, even if it somehow magically absorbed all of the IR without re-radiating, it would still be possible to build IR sensors that detect it: if it's perfectly black in IR, it will show up as a "shadow" against a warmer background. To be invisible to IR, you need a suit that matches its temperature to the surroundings.

On that note, it sounds like you could make a really good heat ex-changer with this stuff. I wonder if this would make for improvements in fields like refrigeration and energy production.

But if it absorbs IR and irradiates a considerable amount of heat at the same time, wouldn't it be considered a lousy, lousy IR absorbent?

Infrared is not all the same. For one thing the frequency depends on the temperature.

But more importantly it absorbs infrared light, and converts it to heat. Heat and light are not the same thing! True, hot things emit light, but that doesn't make them the same thing.

Most practically you can cool the device once the energy is heat. Or just dilute it in a heatsink.

Indeed. In fact, if this low albedo extends over such a wide range in wavelength, this material might be as close to the theoretical concept of a "blackbody" we have seen.

[quote]if you made a suit out of this stuff, and were somehow able to rig it so that all of the heat is dumped inside the suit, then it would be "invisible" to IR sensors. However, it would get really uncomfortable inside that suit really fast.[/quote]

That gave me an idea... if it were possible to make a sphere that had this coating on the outside and dumped the heat to the inside, you'd have a great heat source for a Stirling engine. This could work exceptionally well in space if you can use the light-absorbing sphere oriented so that it shaded the cool side of your engine, thus maximizing the temperature difference.

Car body paint shops could offer it for the darkest matte black on the block.

This might not be such a good idea when you consider that "black cars are 47 per cent more likely to be involved in road accidents".

Source: http://www.telegraph.co.uk/motoring/news/7845366/Black-cars-...

Maybe they just aren't black enough...

But does it blend and can I wear it?

Context is vary important:

During daylight hours, black cars were up to 12 per cent more likely be involved in crashes than white vehicles, while at dawn and dusk, the figure rose to 47 per cent.

There is simply not enough information to say how bad black cars based on that article. If they where significantly safer at night then everything in that article could be true even though black cars where safer overall. Also, because they are using the 'worst case numbers' some makes and or models could be safer when panted black etc. Let alone changes in the type of drivers that chose specific colors. Let alone more complex situations ex: Yellow might be the least safe color for a given driver, but if it's only chosen by safety contentious people due to it's reputation it might have the best record.

Edit: I suspect black cars are moderately less safe, but less than a 10% difference overall otherwise they would just give the actual numbers.

> I could finally have the ultimate set of curtains to ensure cave-like darkness on the brightest day.

BTW, If you really do need this, aluminium foil taped to the windows blocks light completely. It's not a curtain, but if you need it really dark, it works very well.

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