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In a magic setting, a stereotypical "cold fire" might be a deep blue color but otherwise look just like a normal fire, consuming some materials and radiating cold.

In reality, this is not possible for numerous reasons. However, what is the closest thing we could get?

The more bullets we cover, the better the solution is:

  • Cools the surrounding area (Required point)
  • Consumes some material
  • Can consume nearby (commonly found) material for its energy
  • Is a naturally occurring process
  • Has features that warrant the "cold fire" nickname
  • Portable starting materials
  • small in size (for required starting materials), think flint for regular fires
  • emits light (any color)
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    $\begingroup$ Well, "emits light" isn't going to happen. Emitting light in the visible spectrum requires a certain amount of energy and that amount happens to be "warmer than ambient." Unlikely that "consumes organic matter" will succeed also, as while there are endothermic chemical reactions, they don't involve "standard" organic matter (i.e. carbon is not involved). $\endgroup$ – Draco18s Dec 11 '15 at 16:00
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    $\begingroup$ @Draco18s That's fine, I state them to remain complete. Afterall, the answer could be "Air conditioning, with a lightbulb indicating its running" - only achieves cooling and emitting light, but it just happened :P $\endgroup$ – DoubleDouble Dec 11 '15 at 16:06
  • $\begingroup$ Well, I hope you find an answer, but I doubt anything will come sufficiently close. (The AC unit amuses me, however). $\endgroup$ – Draco18s Dec 11 '15 at 16:09
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    $\begingroup$ Well, this is awkward... $\endgroup$ – Frostfyre Dec 11 '15 at 17:00
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    $\begingroup$ You might want to remove "Can consume nearby material for its energy." A "cold fire" would have to decrease the energy of its surroundings, not increase them, so it won't actually consume any energy. Alternatively, it consumes energy like a refridgerator, but then your cold fire has to dissipate a bunch of heat elsewhere (which would basically have to be a fireball) $\endgroup$ – Cort Ammon Dec 12 '15 at 4:32
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After some thought, I thought of something simple, in the same vein as nigel222's answer: dry ice.

  • Cools the surrounding area

The primary use of dry ice is as a cooling agent.

  • Consumes some material

It'll consume itself. Dry ice is a solid that will sublimate at average temperatures.

  • Is a naturally occurring process

Curiously, there is a place on Earth where dry ice could conceivably occur naturally: Antarctica. The processes by which dry ice inflicts burns and cools the environment are purely physics-based.

  • Has features that warrant the "cold fire" nickname

Dry ice is used to make fog in a number of fields, such as stage performances. The unfamiliar could easily mistake the fog for a crawling, white smoke. Also, dry ice burns, as mentioned above.

  • Portable starting materials

Dry ice can be stored in any cooler-like container and handled with thick gloves and it isn't heavy in manageable quantities.

  • small in size (for required starting materials), think flint for regular fires

Dry ice starts itself, once introduced to higher temperatures. You can use hot water to enhance the effect, as indicated in the video.

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  • $\begingroup$ But does it emit light? I've not seen dry ice do that, but it's important for the answer... $\endgroup$ – PipperChip Dec 12 '15 at 8:53
  • $\begingroup$ @PipperChip Dry ice, as far as I know, has no chemiluminescent reaction. However, if the dry ice formed with magnesium inside and someone tried lighting it: (LSU experiment). $\endgroup$ – Frostfyre Dec 12 '15 at 14:04
  • $\begingroup$ A natural source might be a volcanic carbon dioxide vent into a very cold environment (colder than most of antarctica). If so might be contaminated with sulphur dioxide leading to characteristic burnt-sulphur smell as it sublime. Even better if also mixed with finely ground rock (from a glacier?) which is left as "ash". $\endgroup$ – nigel222 Dec 12 '15 at 17:45
  • $\begingroup$ An explanation of dry ice plus water with mediaeval knowledge base. Throw oil on hot fire. Throw water on cold fire. See, same thing! $\endgroup$ – nigel222 Dec 12 '15 at 17:49
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While messing with laws of thermodynamics and 'negative temperature' (which is "hot" in physics) I realised that we have something already that fits a few of your criteria. Lasers!

Cools the surrounding area (Required point)

By utilising methods like doppler cooling, atoms lose momentum equal to the momentum of the photon. When the excited atom releases a spontaneous photon, it's pushed into a random direction, and the overall speed and kinetic energy of the atoms are reduced over time.

We use this process at home to cool things to near absolute zero levels.

Consumes some material

You're consuming energy to emit the laser.

Is a naturally occurring process

NASA's Kuiper Airborne Observatory detected laser light in space. It is not unrealistic to me to find one in nature that may have cooling effects on its surroundings. I can imagine a celestial body that's consuming matter in space but is emitting specific laser light into a nearby cluster of space dust and is such that emulates our doppler cooling at home.

Emits light

Lasers are the epitome of light emitting. A 445 nm laser is blue, which satisfies the colour that you might be looking for.

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  • $\begingroup$ I was going to write an answer, but it ended up being to close to yours. The closest I could find is ultracold plasma, where plasma is created and cooled down to 0.1K using lasers. But then it ended up just being about the lasers since the plasma itself doesn't meet many of the requirements. $\endgroup$ – AndyD273 Dec 11 '15 at 18:51
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    $\begingroup$ This process only cools the point the laser’s pointed at, right? If so, that’s not really the “surrounding area,” it’s just one point. I guess you could have some weird emitter that spits lasers in all directions... Or is this something that does cool the surrounding area, drawing it in and sending it away in the beam perhaps? $\endgroup$ – KRyan Dec 11 '15 at 21:34
  • $\begingroup$ @KRyan Perhaps a spherical (or nearly spherical polyhedral) object that emits lasers in all directions? $\endgroup$ – ApproachingDarknessFish Dec 12 '15 at 3:07
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    $\begingroup$ "We use this process at home to cool things to near absolute zero levels." I'm pretty sure that's on the official list of things not to do at home $\endgroup$ – Journeyman Geek Dec 12 '15 at 11:03
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    $\begingroup$ @JourneymanGeek You're assuming s/he doesn't live at a laboratory. $\endgroup$ – Frostfyre Dec 12 '15 at 14:06
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Fire is an exothermic reaction. Exothermic means that while material are converted into others (fuel and oxygen into smoke and ashes), heat is created as a by-product.

There are also endothermic reactions in chemistry. These are chemical reactions which don't create heat but consume heat instead. That means they cool down the surrounding. So what you need is a (likely fictional) chemical which reacts endothermic with a very wide range of common substances.

However, these reactions won't cause a blaze. A blaze is a plasma. A plasma is heated gas. Gas does not turn into plasma when it cools. Also, it won't create any light.

But when the endothermic reaction cools the surrounding enough, you might see humidity in the surrounding air condense, which could cause a visible cloud of fog to appear around it.

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    $\begingroup$ It wouldn't surprise me if there were endothermic chemiluminescent processes out there... $\endgroup$ – Shalvenay Dec 12 '15 at 4:09
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You might consider various small molecules that condense to liquid at temperatures well below the freezing point of water. If you survive an attack with (say) liquid nitrogen you will report the pain of severe frostbite as being like fire.

Alternatively choose an inflammable such as liquid propane. Cold until ignited. Then fire or explosion.

I think there may even be liquids that self-ignite once they vaporize and mix with air. Most I can think of are also toxic. Don't know if there's one that could combine all of frostbite, chemical burn, and true hot fire on ignition. Liquid ammonia (anhydrous not solution) comes close but does not self-ignite. Add a trace catalyst? At this point my chemistry knowledge runs out.

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Okay… here’s an idea I had a long time ago: it does not emit light, it does the opposite.

Hear me out: light consists of photons, they are something like tiny concentrated energy bolts, they carry both light and heat at the same time (ever seen lightbulbs burn hot?) Heat is light and light is heat.

So if we are looking at antifire that consumes energy (heat), you could also make it consume light… Cold is darkness and darkness is cold. This thing would look exactly like flames, but they originate away from the centre of the reaction and converge towards it, they are black and get blacker towards the centre. The whole thing emits darkness (imagine that it attracts light into itself and redirects it from hitting surfaces around). Then consumption. In a fire, you see matter getting broken down and energy is released. In this antifire thing, you could imagine that the energy it consumes is used to bunch up matter. In other words, it would consume smaller particles to create larger bundles of matter (think of how wood turns to ash, but in reverse — ash turns to wood). Maybe it produces fibers or whatever that get dissolved in liquid air (it’s cold, right?) and this flows around from under the antifire in streams. As the air evaporates when it gets farther from the source of cold, the fibers are deposited, so instead of having a candle that burns down, you get antifire which builds its own candle up underneath/around it.

Not sure about starting materials. You may have to create some fictional ore that can start this process with an “antispark” or such. To stop this process, you’d probably need vacuum, so that it runs out of “raw resources” from which to build its product material. Then it would have nowhere to deposit the energy it collects and potentially go out with an explosion, releasing all the excess energy. As a twist, before going out, you can make it reuse its “product” material to make heavier/more complex material. For example, if it combines hydrogen into heavier atoms, it can go all the way to Ununoctium until it runs out of matter. Its preferred product would obviously be the simplest it can create from the matter/energy at hand.

Source: an art project I did in high school was a drawing of a world in which light and dark are switched, so wherever there is conventionally light there is now shadow and vice versa. This idea kept coming back to me ever since until I formed it into the concept I described above.

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You are making a simplistic assumption of what fire is. You are asking for some things that are similar to fire(consuming something), and some things that are the opposite of it(cooling the surroundings).

In reality, fire is just a chemical reaction of oxidation; a reaction which causes something(reactant) to bond with oxygen, and produce an oxide and radiate light and heat in the process.

An endothermic reaction will have reactants combine with something and instead of radiating heat, will absorb heat. Because it's absorbing energy when the reaction is happening(instead of radiating), we cannot have something that glows.

Oxidation(combustion) is a common reaction for most of the material we find around us(which is carbon based, so it reacts with oxygen easily). Unfortunately, there isn't any endothermic reaction(AFAIK) that's so common.

As for being small and portable, I agree that dry ice will be a viable candidate, as Frostfyre said.

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  • $\begingroup$ What do you mean by 'useful', then? I just pointed out that some of your assumptions are incorrect. $\endgroup$ – cst1992 Dec 16 '15 at 5:18
  • $\begingroup$ And no, I didn't base my answer on contents of that comment; I hadn't even read it till you pointed it out to me. $\endgroup$ – cst1992 Dec 16 '15 at 5:25

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