Half a croissant, on a plate, with a sign in front of it saying '50c'
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Maxwell's Luminous Refrigerator

Paint so white it freezes everything it's painted on
  [vote for,

I am convinced this won't work but I don't know why.

This is a layer of substance which draws power from the vibrations of the molecules on the surface of the object on which it's painted. If a molecule moves towards the layer, it powers the substance and causes it to emit "ultra- white" light in a manner similar to that imagined in the ultraviolet catastrophe, in a wide range of wavelengths visible and invisible. This removes the kinetic energy of the vibrating molecules next to the layer and entropy causes the heat, expressed through vibration, within the object to spread out. At the same time, the layer is effectively opaque to electromagnetic radiation from outside, or at least it absorbs less energy in the form of electromagnetic radiation than the energy it emits. This constantly cools the object, taking it ever closer to absolute zero.

I suppose I want to ask two things about this:

* Why is this theoretically impossible? I'm pretty sure it must be but I can't see why.

* How might this happen? For instance, how could this be a good insulator, or perhaps opaque enough, and is there a way molecular vibrations of this kind, or just heat per se, could be used to power a light source?

Leaving reason aside for a moment, I'm imagining a hypothetical refrigerator which is one simply because it's literally a "white good". It's just a cupboard painted with ultrawhite luminous paint which therefore constantly cools its interior by virtue of its colour alone.

nineteenthly, Apr 30 2016

Short treatise on this topic. https://www.youtube...watch?v=VnbiVw_1FNs
[MaxwellBuchanan, Apr 30 2016]

Maxwell_27s_20Demon_27s_20Demon [FlyingToaster, Apr 30 2016]

Physics Appeal Court Physics_20Appeal_20Court
Sue someone ! [8th of 7, Apr 15 2017]


       All you need is some of that special one-way glass that doesn't exist, and this will work just fine.   

       You are asking for a paint that either emits better than absorbs, or which can magically upconvert low- grade infra-red to some shorter wavelength. That is why it won't work.
MaxwellBuchanan, Apr 30 2016

       // upconvert low- grade infra-red to some shorter wavelength. //   

       Theoretically, there are optical (quantum computing) technologies that could upshift three low-energy photons into two higher-energy ones (but with overall energy loss), though entropy will always get you in the end.
8th of 7, Apr 30 2016

       Yes, and there's two-photon fluorescence; but none of those will help here.   

       I refer the ensteamed [nineteenthly] to Professors Flanders and Swann, who addressed this very topic. <link>
MaxwellBuchanan, Apr 30 2016

       Hmm, you've conflated a couple different mechanisms....   

       "whiter than white" - promoted on laundry detergent commercials - is a fluorescing downshift: the UV - which we can't see - from the sun, hits a substance which absorbs the UV photon, re-emits a lower-energy photon (in the visible light spectrum, which we can) and keeps the change as internal heat. It's the same reaction as a blacklite poster. If human beings saw in the UV spectrum as well it wouldn't look any brighter, compared to the ambient light.   

       I took a few stabs at it myself: the first two used symmetrical shifts and were easily dismissed; the latest, unassailable thus far (except by circular reasoning) also uses fluorescing as a mechanism <link>
FlyingToaster, Apr 30 2016

       Leaving reason aside for a moment [marked-for-tagline]
Toto Anders, Apr 30 2016

       The antithesis of this is a cupboard painted with ultrablack absorbing paint that gets hotter and hotter. Or to put it on galactic scales, where density and heat blur, a white hole and a black hole.   

       so probably works just not at our scale. Yet.
wjt, Apr 15 2017

       I wonder if on both very small and large scales it works, but not between the two. Random happenings on a small scale do things like the Casimir Effect and on a large scale and a small one there's the ergosphere. The trick would be to edge each towards each other and pounce.
nineteenthly, Apr 15 2017

       // painted with ultrablack absorbing paint that gets hotter and hotter. //   

       ... until it is in equilibrium with its environment.   

       "ultrablack" coatings are both an excellent absorber and an excellent emitter - typified by the "black body" radiator concept.   

       The structure will absorb incident energy until its re-radiated emissions due to surface temperature balance the input.
8th of 7, Apr 15 2017

       Reminds me of [Vernon]'s IKECE, which is supposed to be a better radiator than absorber IIRC (and a better-than-black radiator in any case).   

       // The antithesis of this is a cupboard painted with ultrablack absorbing paint that gets hotter and hotter. //   

       The laws of optics say that if you have one object emitting radiation thermally and another absorbing it, you cannot have any optical system (that doesn't add energy of its own) that results in the absorber getting hotter than the emitter. This is an adaptation of one of the laws of thermodynamics.
notexactly, Apr 15 2017

       However, if you feel the laws of thermodynamics are being applied unfairly, there's always <link> ...
8th of 7, Apr 15 2017

       Aren't Laws of Thermodynamics for objects this side of the event horizons? Black holes can be very small and so, assuming symmetry, would white holes.
wjt, Apr 15 2017


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