# What is the opposite of FIRE ? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [November 29, 2009, 9:30pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379 "2009-11-29T21:30:45Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [November 30, 2009, 5:05pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/21 "2009-11-30T17:05:30Z")
> [@zut](#): > > Is it possible to construct a chemical process where carbon dioxide and water (the two main products of combustion) are re-combined to make oxygen and some sort of fuel, realizing that this process will require a net input of energy? Not only is it possible, but we’d all starve without it. You’re just talking about photosynthesis. We do not currently have a man-made machine like the OP is asking for, and we probably won’t for quite a few years (or decades), but we certainly understand how it can be done. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [November 30, 2009, 5:29pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/22 "2009-11-30T17:29:07Z")
**zut** said: > [@](#): > > Is it possible to construct a chemical process where carbon dioxide and water (the two main products of combustion) are re-combined to make oxygen and some sort of fuel, realizing that this process will require a net input of energy? Yes. It’s called a “tree”. You didn’t specified that the fuel had to be liquid. **QuestionMark** said: > [@](#): > > Imagine a car, > in second gear, on a mountain, and rolling backwards. > The engine turns backwards… > makes vacuums… > pulls in dirty air… You really don’t understand much about how a car works, or how chemistry works. Hint: it doesn’t work that way. You can’t run a car backwards and make the chemical reaction run backwards. Doesn’t happen. Cars cannot suck gases in through the exhaust line and force them together in the engine. Cannot happen. It would be like getting on a bicycle on a hill, rolling down the hill, and letting the pedals move your feet, so that at the end of the ride you are less hungry. You can’t put energy into your body by moving your feet, you can’t put fuel into a car by turning the cylinders externally. The word “opposite” is also unclear in this context. For example, what is the opposite of juggling? How do you un-juggle something? **qbadger** has provided probably the closest answer to what you want. “Fire” is the rapid release of energy through an oxidation process. The opposite of that process is going to be some kind of endothermic reduction, i.e. a chemical reaction that absorbs energy and releases oxygen. Like I said, photosynthesis. The real question is what are you trying to achieve? A form of transportation? An environmental clean up device? > [@](#): > > Maybe it can bring down the temperature of the air as well. > > I don’t really believe in the CO2 problem, the temp-rize because of that. (Less than 1 degree in so many years). > No. > > We’ve been burning fuels and things for so many years now. > That’s where the heat comes from. > > This must be reversable. > So I say: it’s do-able. Your idea is that by burning fuel (cars, industry, stoves and ovens, water heaters, campfires, etc), we have been adding heat to the atmosphere, thus warming the Earth. And this is the heat that is making the whole Earth warmer, i.e. global warming. So if we somehow run fire backwards, instead of releasing heat into the atmosphere we will draw heat out of the atmosphere? I won’t dispute that heat released from chemical reactions goes into the atmosphere and warming the Earth. I will dispute that the amount of heat released in this manner is significant in the overall temperature of Earth. The heat we experience comes from two major sources: the Sun, and the core of the Earth. Radioactive decay from within the Earth is producing some heat, and solar absorbsion is the rest. However, the Earth has a built in cooling mechanism - it’s called “radiating to space”. Energy from the Sun warms the Earth by being absorbed, but some of that Solar energy is reflected away. Changes in the reflectivity of Earth’s features will make more of that energy reflected away (e.g. smog makes more clouds which reflect light, glaciers are snow and ice which are white and thus reflect more light than brown ground or green plants, etc). But any object will radiate energy based upon its temperature. The Earth is dumping heat into space via this radiation. The key is the balance between energy into Earth and energy leaving Earth. Radioactive decay is something of a constant until all the materials are expended. But how much energy is absorbed from the Sun vs reflected by the Earth does vary. But the real key to Global Climate Change (i.e. global warming) is “the Greenhouse Effect”. The Earth radiates heat via infrared radiation based upon the global mean temperature. But how much of that energy leaves the atmosphere depends upon the composition of that atmosphere. Carbon dioxide is the right size such that the infrared radiation is absorbed and thus contained within the Earth’s atmosphere, not released to space. Releasing it to space would cool Earth, but trapping it in the atmosphere traps it on Earth, keeping Earth warmer. I’m still thinking about the other part of your plan. If we were to increase the plant cover of Earth, would that photosynthesis be using energy already being trapped by Earth, and thus reduce the total amount of heat in the atmosphere? How much of a benefit would that be? ---
**Author:** ![Mr.Moto](https://avatars.discourse-cdn.com/v4/letter/m/9de0a6/32.png) [@Mr.Moto](https://boards.straightdope.com/u/Mr.Moto)\ **Post date:** [November 30, 2009, 6:28pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/23 "2009-11-30T18:28:40Z")
Fire is the devil’s only friend. The opposite of the devil is Jesus. What a friend we have in Jesus. The opposite of fire is us. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [November 30, 2009, 9:02pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/24 "2009-11-30T21:02:32Z")
> [@Irishman](#): > > I’m still thinking about the other part of your plan. If we were to increase the plant cover of Earth, would that photosynthesis be using energy already being trapped by Earth, and thus reduce the total amount of heat in the atmosphere? How much of a benefit would that be? At any rate, additional photosynthesis would reduce the CO[sub]2[/sub] level. ---
**Author:** ![qbadger](https://avatars.discourse-cdn.com/v4/letter/q/fbc32d/32.png) [@qbadger](https://boards.straightdope.com/u/qbadger)\ **Post date:** [December 1, 2009, 3:09pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/25 "2009-12-01T15:09:06Z")
Article you may find interesting: > **[Trees in far north provide biggest climate benefit](https://www.newscientist.com/article/mg20427343-900-trees-in-far-north-provide-biggest-climate-benefit/)** > > Planting forests in the tropics could be a waste of time and money, compared with planting them at high latitudes Afforestation should lead to lowering of albedo, which means more light is absorbed (and therefore heat/energy). This will offset the benefit of carbon sequestering. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [December 1, 2009, 3:41pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/26 "2009-12-01T15:41:01Z")
**John W. Kennedy** said: > [@](#): > > At any rate, additional photosynthesis would reduce the CO2 level. Sure, and I should have mentioned it. ---
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [December 1, 2009, 10:37pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/27 "2009-12-01T22:37:23Z")
I thought fire was rapid oxidation hence the opposite would be rapid reduction - wouldn’t it? ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [December 1, 2009, 10:49pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/28 "2009-12-01T22:49:36Z")
> [@qbadger](#): > > Article you may find interesting: > [http://www.newscientist.com/article/mg20427343.900-trees-in-far-north-provide-biggest-climate-benefit.html](http://www.newscientist.com/article/mg20427343.900-trees-in-far-north-provide-biggest-climate-benefit.html) > > Afforestation should lead to lowering of albedo, which means more light is absorbed (and therefore heat/energy). This will offset the benefit of carbon sequestering. That summary does not say whether account was taken of the portion of that additional absorption that is consumed by photosynthesis, rollin’ that ol’ CO[sub]2[/sub] rock up Sugar Hill. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [December 2, 2009, 12:31am UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/29 "2009-12-02T00:31:08Z")
> [@QuestionMark](#): > > But I would like to know: > —\>What is the opposite of FIRE ? > (Thinking of a car’s engine). The opposite of FIRE is ERIF. (Thinking of preparing four cheese lasagna for dinner.) ---
**Author:** ![dropzone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dropzone/32/7515_2.png) [@dropzone](https://boards.straightdope.com/u/dropzone)\ **Post date:** [December 2, 2009, 2:41am UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/30 "2009-12-02T02:41:32Z")
Yeesh, the four elements are earth, water, fire, and air and, on the [same chart](http://en.wikipedia.org/wiki/File:Four_elements_representation.svg) ANY educated person should know, the opposite of fire is water. Doesn’t anybody study science anymore? ---
**Author:** ![EvilTOJ](https://avatars.discourse-cdn.com/v4/letter/e/ee59a6/32.png) [@EvilTOJ](https://boards.straightdope.com/u/EvilTOJ)\ **Post date:** [December 2, 2009, 8:09am UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/31 "2009-12-02T08:09:36Z")
That post coming from someone on the SD’s Science Advisory Board made it just a little more amusing than normal. I chuckled. ---
**Author:** ![enigmatic](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@enigmatic](https://boards.straightdope.com/u/enigmatic)\ **Post date:** [December 2, 2009, 12:32pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/32 "2009-12-02T12:32:00Z")
Plus, lets imagine that we do have a “reverse car” that operates in the way you speculate, (lets call it sufficiently advanced technology :D). Now what. How do you get the car up the mountain? because if you are expecting people or animals to haul them up there you need to consider the amount of energy that will be used in producing food for them. You also need to realise that even if the human race devoted every last second of it’s time to hauling cars up mountains it would only be a drop in the ocean compared to previous CO2 release, given the amount of time it takes for a team of people to haul a car up a mountain compared to the time that those same people would have spent (individually) driving the same distance. But on the plus side everyone would be too busy hauling cars to drive anywhere else ;). ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [December 2, 2009, 12:42pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/33 "2009-12-02T12:42:15Z")
> [@](#): > > What is the opposite of FIRE ? Ceasefire? ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [December 2, 2009, 4:07pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/34 "2009-12-02T16:07:20Z")
**janeslogin** said: > [@](#): > > I thought fire was rapid oxidation hence the opposite would be rapid reduction - wouldn’t it? The problem is in the application of “opposite”. You seem to think the opposite part applies to the reaction, but not the timing of the reaction. Others have stated that the opposite applies to the timing of the reaction as well. So they think it is a _slow_ reduction process. YMMV, IANAchemist. ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [December 2, 2009, 4:22pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/35 "2009-12-02T16:22:57Z")
> [@QuestionMark](#): > > On > —\>What is the opposite of FIRE ? You guys are all looking at this the wrong way! The opposite of FIRE is HIRE!😃 ---
**Author:** ![StusBlues](https://avatars.discourse-cdn.com/v4/letter/s/dc4da7/32.png) [@StusBlues](https://boards.straightdope.com/u/StusBlues)\ **Post date:** [December 2, 2009, 4:36pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/36 "2009-12-02T16:36:06Z")
Thanks to the above for photosynthesis as an example. I was thinking of water electrolysis myself. The product of hydrogen burning is water, so tearing the water apart again to release free, flamable oxygen would be the opposite of fire in that case. Photosynthesis is a more general example, though. ---
**Author:** ![QuestionMark](https://avatars.discourse-cdn.com/v4/letter/q/a6a055/32.png) [@QuestionMark](https://boards.straightdope.com/u/QuestionMark)\ **Post date:** [December 2, 2009, 5:10pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/37 "2009-12-02T17:10:11Z")
> [@enigmatic](#): > > . > But on the plus side everyone would be too busy hauling cars to drive anywhere else ;). That really was funny. Thanks! I was asking myself “What is the opposite of fire” because I was thinking about an engine, like one in a car, where fire is ‘added’ to make explosions, etc. If there would be a large scale factory, that would do the opposite of this car-engine, so it would produce oil and clean air, how would the proces work? Somewhere in there, we would have … right? Something like decompressing and freezing, and “un-mixing”. Still think it’s do-able. Something else: I’m Dutch. I made a website page in English. It should be checked on language. Can I mention the page here, or not, or maybe in another post? (It’s about stop smoking). ---
**Author:** ![Larry\_Borgia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/larry_borgia/32/156_2.png) [@Larry\_Borgia](https://boards.straightdope.com/u/Larry_Borgia)\ **Post date:** [December 2, 2009, 5:22pm UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/38 "2009-12-02T17:22:42Z")
What is the opposite of FIRE ? An air-conditioner? ---
**Author:** ![qbadger](https://avatars.discourse-cdn.com/v4/letter/q/fbc32d/32.png) [@qbadger](https://boards.straightdope.com/u/qbadger)\ **Post date:** [December 3, 2009, 12:53am UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/39 "2009-12-03T00:53:54Z")
> [@John\_W.Kennedy](#): > > That summary does not say whether account was taken of the portion of that additional absorption that is consumed by photosynthesis, rollin’ that ol’ CO[sub]2[/sub] rock up Sugar Hill. My understanding is that carbon sequestering refers to the net effect of photosynthesis and cellular respiration, i.e. the carbon in trees comes from some of the carbon in the photosynthesis reaction. I have to admit being quite sketchy with this, so please correct me if I’m wrong. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 3, 2009, 1:01am UTC](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379/40 "2009-12-03T01:01:23Z")
> [@QuestionMark](#): > > Still think it’s do-able. Unfortunately, optimism alone can’t make this work, and nothing else is in your favour. [Previous page](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379.md?page=1) [Next page](https://boards.straightdope.com/t/what-is-the-opposite-of-fire/519379.md?page=3)