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1627
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Fire In Zero Gravity (i.imgur.com)

submitted ago by _repost_

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[–]crashmd 255 points256 points ago

Explain yourself!

[–]ztluhcs 713 points714 points ago

Oh man. Studying combustion science is about to pay off. I've even done a little work on microgravity combustion (what we are seeing here).

Basically in a normal flame you have hot combustion products which are less dense than the surrounding air so buoyancy makes them rapidly move upwards. As this is happening they are cooling down and there isn't enough time to complete combustion so soot is formed. Blackbody radiation from the soot is the characteristic orange part of the flame that we are used to seeing.

In microgravity there is no buoyancy-induced convection so what you see is a pure diffusion flame. That means that there is a thin interface in a sphere around the vaporized fuel stream where the fuel and oxidizer is perfectly mixed to make combustion take place. the fuel burns nearly completely without being pulled away by buoyancy effects, thus you just see a sphere of perfect blue flame.

[–]bizfamo 350 points351 points ago

now like im five

[–]rincon213 361 points362 points ago

I'll give it a shot:

Here on Earth, flames look the way they do because as the match burns, the air becomes very hot and rises. The rising air brings the flame up and away from the match. Because it's carried away, it cools and it doesn't get a chance to properly burn, which results in the orange/yellow flames we are used to.

In the zero gravity picture, the hot air produced by the flame doesn't rise because there is no gravity. Therefore, the combustion is able to stay near the fuel source (the match stick) and burn really hot & efficiently.

[–]PiscesFTW 168 points169 points ago

Now like I'm Calvin.

[–]khrak 435 points436 points ago

All fire is made from energy that leaks out of the Sun as light. Being from the Sun, all fire naturally wants to return there. While on Earth, the fire knows which way to travel to get closer to the Sun, the opposite direction of gravity! The problem is once you're out in space, there is no gravity to guide the flame's direction. As a result, if you light a flame inside a closed spaceship it will become confused as to where the Sun is, and, with no idea as to which direction to travel, remain as a small ball until exposed to the Sun's light.

[–]dreinn 94 points95 points ago

You are brilliant.

[–]Aww_Shucks 32 points33 points ago

You mean he is bright.

He is the Sun's light to our lowly flames.

Guide us, oh bright one!

[–]Penny_is_a_Bitch 11 points12 points ago

Haiku fail?

[–]Aww_Shucks 33 points34 points ago

Never intended

to write that as a haiku

Though, I was quite close.

[–]reble02 1 point2 points ago

Praise be to the Lord of Light

[–]Mckerlie 0 points1 point ago

If only I could be so grossly incandescent!

load more comments (2 replies)

    [–]NutmegLiver 19 points20 points ago

    Tell it to me in Star Wars.

    [–]Duffalpha 22 points23 points ago

    The force is, like it is with all things, a part of the flame. When you light a candle the force surrounds the flame, flows through it. Everything is intertwined. On a planet, the force has a very strong presence. On some of most remote jungle planets like Dagobah and Dathomir, even an individual not sensitive to the force can almost feel it streaming and surging all around. Binding the life together.

    The force that surrounds the candle's flame is affected by this vortex of streaming life, and since fire is such a gentle and soft, almost weightless, thing, it can be caught up in this vortex causing the candle to burn bright.

    In space there is little of anything, and sometimes the raging river of the force slows to a stream's crawl. When someone lights a candle in space, the flow is not strong enough to flicker the flame to brightness.

    [–][deleted] 5 points6 points ago

    and sand. lots of fucking sand.

    [–]Bobdor 0 points1 point ago

    I don't like sand. It's coarse and irritating and it gets everywhere.

    [–]thescientists 0 points1 point ago

    This is getting serious.

    Someone do it in Yoda.

    [–]willyoublend 40 points41 points ago

    In zero-gravity there is only the original trilogy, therefore everything goes perfectly.

    [–]burnsse1 7 points8 points ago

    Don't get cocky, kid.

    [–]sn1p3rb8 14 points15 points ago

    midi-chlorians

    [–]sirus20x6 2 points3 points ago

    A long time ago space flame masters harnessed fire in perfect spherical harmony, but here on our planet renegade flame lords choose quicker mixing yet imperfect combustion ratios to further their evil needs. It's up to you the son of the most powerful evil flame lord to set combustion right into the universe and preserve balanced stoichiometry

    [–]unorthodoxme 2 points3 points ago

    Something, something, something, darkside. Something, something, something, complete.

    [–]SaltySulks 4 points5 points ago

    The fire is trying to escape Jar Jar Binks, but in space Jar Jar Binks cant survive so the flame doesn't need to run away.

    [–]Thereal_Sandman 0 points1 point ago

    Han shot first.

    [–]Hartech 7 points8 points ago

    Do NOT light a flame in a closed spaceship

    [–]mtbmike 8 points9 points ago

    they burn incense and smoke cigars in Promethius and they're fine.

    [–]Nebulaoblivion 1 point2 points ago

    Its science fiction, so on their ship somewhere they have something which creates new oxygen, in real spaceships all of your oxygen is recirculated, if you light a flame it burns away oxygen making it harder for everyone to breath, the smoke has nowhere to go so you're stuck with it.

    Additionally since you're stuck with tobacco or incense floating around it will eventually clog the ventilation systems, have you seen those pictures of the inside of smokers computers? That would be in all the air filters of the ships.

    Unless I'm terribly mistaken, I'm no rocket scientist or anything.

    [–]illogicaldolphin 4 points5 points ago

    I wouldn't cite Prometheus as a good example of plausible science fiction...

    [–]mtbmike 1 point2 points ago

    for the record - i was being sarcastic. maybe if i use italics for sarcasm people will get it better.

    [–]AskingOnce 6 points7 points ago

    I think you should check out /r/shittyaskscience - your people are waiting.

    [–]crkhobbit 8 points9 points ago

    But what about at night.!?!?

    [–]TehDingo 7 points8 points ago

    Easy. The moon is basically a giant mirror for the sun, so fire just travels to it insteadd

    [–]morpheousmarty 0 points1 point ago

    reddit has done well today, upvotes and monocles for all you find commenters.

    [–]ErnestMorrow 2 points3 points ago

    The moon reflects the sun's light and tricks the flame.

    [–][deleted] 2 points3 points ago

    Yeah... especially since there's far more incentive to set things on fire at night than during the day.

    YOU SIT ON A THRONE OF LIES, KHRAK.

    [–]handbannana 2 points3 points ago

    Now like I'm watching Bill Nye

    [–]kinnaq 2 points3 points ago

    Bill! Bill! Bill! Bill!

    [–][deleted] 1 point2 points ago

    Now like Im a scientologist.

    [–]samjowett 8 points9 points ago

    Xenu, man. It's fucking Xenu in his spaceship. It's his birthday and so he gets cake with a candle on it. And on that candle: a single blue sphere of flame. And from his eye a single teardrop forms and floats into the zero gravity.

    So anyway yadda yadda yadda thetans and ghosts of aliens and psychiatry is a crock, etc.

    Now give me $1200.

    [–]kinnaq 3 points4 points ago

    You had me at $1200... You had me at $1200.

    [–]Up_Yours_Sir 2 points3 points ago

    Nice try, Tom Cruise!

    [–]DiogenesK9 1 point2 points ago

    Now like I'm John Madden!

    [–]samjowett 1 point2 points ago

    Well you see the flame is a lot like Brett Favvvre. And the gravity is like the Green Bay Packers. The Green Bay Packers need Brett Farrvverer. And Brett Favvreer needs the Green Bay Packers AND gravity! You know what I mean. And I mean why would Brett Faverrer be in space anyway? You can't throw touchdown passes in space! <chuckling> I mean it would be good it you could. People could I mean people could play football on the moon!! Brett Farrvre could be the first best quarterback on the the the moon and then argh <garbled> and whoever gets the most points wins! Youknow what I mmmnd <garbled> yadda yadda TOUCHDOWN!!!!!

    [–]redbeard8989 1 point2 points ago

    Now like i'm Hobbes

    [–][deleted] 4 points5 points ago

    Now explain it to me really condescendingly.

    EDIT: wow, people apparently really suck at this.

    Okay guys, let me make this clear for you. Condescending means you talk DOWN to them.

    [–]illogicaldolphin 6 points7 points ago

    I would explain, but you wouldn't understand.

    [–]Skulder 2 points3 points ago

    You'll understand when you're older.

    [–]Up_Yours_Sir 1 point2 points ago

    Hot air doesn't rise in zero-g. DUHHHHHHHH

    [–]w0bb 1 point2 points ago

    Don't worry your little head about it.

    [–]SlugsOnToast 2 points3 points ago

    Now like I'm Hobbes.

    load more comments (2 replies)

      [–]Calvinb27 8 points9 points ago

      I resent that

      [–]cynicalMIND 8 points9 points ago

      wait what does gravity have to do with the hot air not rising? wouldnt a lack of gravity make it rise even faster? sorry if i sound like a complete idiot

      [–]prosequare 13 points14 points ago

      No gravity means: Nowhere to rise from. Every direction is equal. There is no up or down in zero/microgravity.

      clarification: Gravity causes hot gases to rise because they are less dense than the cool gases surrounding. Without gravity, hot gasses will still expand as they become less dense but the expansion will happen in all directions.

      [–]cynicalMIND 7 points8 points ago

      okay thanks that makes much more sense I guess I was just looking at it the wrong way

      [–]Para_Salin 0 points1 point ago

      So gravity causes convection? I thought it had something to do only with how energetically charged the atoms/molecules are. The more heat is available, the faster they move around and the gas expands. The more cooler the particles are, the less they move the lesser the expansion.

      I would have thought in this case that the effect would have been different - that the flame would actually looked wider on top (expanding gases rising without gravity) and narrower at the bottom. Sorta like a funnel shape maybe...

      [–]prosequare 1 point2 points ago

      You are correct about convection, but you are missing the part about why convection on earth works the way it does. Under the influence of gravity, those heated gasses, being less dense than surrounding air, rise because they are more buoyant. What's important is the frame of reference. Here on earth, gravity gives us 'up'. In space, there is no up. There is no 'rising' because in order to rise, a thing has to go up. So the heated gases expand, just like on earth, but instead of rising, they expand outward until an equilibrium is met between combustion products expanding and the outer edges cooling and contracting.

      Sorry if that doesn't help, I'm typing on my phone.

      [–]Para_Salin 0 points1 point ago

      Thanks for your answer, I think I get it now :)

      [–][deleted] 2 points3 points ago

      Let me know if their explanations are sufficient since there are a few concepts that may still be difficult to grasp, but I don't want to write it out if you don't need it.

      [–]sam_hammich 1 point2 points ago

      Gravity keeps the atmosphere around us, and so around the flame. With no gravity to allow less dense objects to rise above denser objects, the flame does not rise.

      load more comments (3 replies)

        [–]CB304 2 points3 points ago

        But what makes the flame blue instead of read? Sorry if I did not understand that aspect, I guess I'm just stupid.

        [–]nylee23 2 points3 points ago

        I think that has to do with the blackbody radiation mentioned. Essentially, blackbody radiation is a type of light that's emitted by anything with a temperature. It's the type of light we receive from stars, and actually all humans emit blackbody radiation as well (in the infrared). The color, or wavelength, of the radiation is related to the object's temperature, so the cooler parts of the flame that don't have time to finish combustion (near the top) are orange. But, in the zero-gravity situation, everything has time to complete combustion, so it's at a higher temperature.

        You can actually already see this effect by just looking at the candle in gravity. It goes from blue near the wick (the hottest part) to orange/red far from the wick (the coolest parts).

        [–]CB304 0 points1 point ago

        Thanks!

        [–]telekyle 1 point2 points ago

        Thanks Jack.

        [–]ravkal 1 point2 points ago

        Does this mean that the match will burn longer? If yes, how much longer?

        [–]rincon213 1 point2 points ago

        This is an educated guess, so someone correct me if I'm wrong.

        The match in space is blue because it has a chance to burn much more efficiently. Because of this, I would assume it's able to burn through the fuel at a much faster rate.

        [–]AnonUhNon -1 points0 points ago

        This is all good and well but oxygen is required to burn something, correct? You can't just float out into space and light a match, right?

        [–]dirtygrandpa 52 points53 points ago

        Zero-gravity doesn't mean zero-oxygen

        [–]bioemerl 2 points3 points ago

        wouldn't the lack of movement of the flame cause oxygen to not be replenished as the air circulates? (or because it does not.)

        [–]Ugbrog 7 points8 points ago

        Air circulates and mixes naturally. The higher temperature of air at the interface of flame is going to result in higher energy in nearby gases, and a more rapid rate of mixing.

        [–]biggmclargehuge[!] 1 point2 points ago

        The room is still pressurized and as such will circulate as the flame burns. I would imagine if this were a video the flame would still flicker as it does here on Earth (though while still maintaining the unique blue domed shape) because the air circulation in the room they're testing this in is not exactly zero.

        [–]rincon213 0 points1 point ago

        The flame would consume the oxygen, which would make a gradient of lower concentration near the match, to higher (normal) concentration further from the match. The concentration gradient would cause oxygen mass transfer towards the match, keeping the flame going.

        [–]AnonUhNon 8 points9 points ago

        Just making sure!

        [–]Ninj4s 5 points6 points ago

        You are correct. And i'm sure there are rules against lighting matches on the ISS and other space places. Except for maybe scientific purposes of course.

        [–]yarrpirates 1 point2 points ago

        Yep, a flame needs a fuel source, an oxidiser (in this case, oxygen from the air) and heat. Once it's lit, it provides its own heat.

        [–]Annoyed_ME 3 points4 points ago

        You could light a match in space, you just couldn't keep it burning past the head, as you would run out of the oxidizing agent. Also, oxygen isn't required to burn something. Oxygen is one of many possible oxidizers out there.

        [–][deleted] ago

        [deleted]

        load more comments (2 replies)

          [–]LettersFromTheSky 0 points1 point ago

          So space travel should be really efficient right?

          [–]Para_Salin 0 points1 point ago

          Could you maybe explain why gravity affects the shape of the flame? I mean

          ...the hot air produced by the flame doesn't rise because there is no gravity.

          That part I don't get. I thought hot air rises because it is less dense than cold air. If that is true, then what part does gravity play here?

          [–]Para_Salin 1 point2 points ago

          Please disregard this question - it was already posted before.

          load more comments (20 replies)

            [–]ztluhcs 11 points12 points ago

            Whenever I think of buoyancy, which is really the heart of the problem here, I like to think of boats. Why do boats float? It's because they push water out of the way, and the water that they push out of the way pushes back on the boat even more (since it weighs more) which makes the boat float at the top of the water.

            In a normal candle flame the same thing is going on. The trick to it is that when air gets hot it pushes the cool air out of the way just like a boat! Then the hot air floats to the top just like a balloon filled with air would if you took it to the bottom of a swimming pool. As the hot air floats upward, it starts to cool down, which makes that orange color.

            In the second picture there is no gravity. Now, if there were no gravity, boats wouldn't float. There just wouldn't be any difference between the boat and the water since without gravity there is no such thing as weight! So none of the floating air business I talked about before happens in the second picture. The candle wax gets turned into gas by the heat of the flame, which then mixes with air and burns up in a little blue sphere. In many ways, the second picture is much simpler than the first! We live in a pretty incredible world.

            [–]awprettybird 2 points3 points ago

            Please tell me you are a science teacher.

            [–]ztluhcs 1 point2 points ago

            Still merely a student...

            [–]awprettybird 2 points3 points ago

            ah, well, Good luck in your studies and I hope you keep that passion for science. I think you have a talent for explaining things in a way that lay-people like myself can really understand it.

            [–]Dedalus2k 2 points3 points ago

            Here is What Is A Flame as explained for an eleven year old Alan Alda from his Flame Challenge.

            http://vimeo.com/40271657

            [–]DELTATKG 1 point2 points ago

            In normal situations, materials don't burn as completely, and so not as hot. This is because they get away before they can burn completely.

            I don't quite understand what microgravity is and all that, so I won't attempt to explain it.

            [–]ztluhcs 1 point2 points ago

            Microgravity is just small gravity. In this case you could either be in space or you could just burn a candle while it is in free fall to create a microgravity environment.

            [–]dont_press_ctrl-W 1 point2 points ago

            Microgravity is just the more-technically-correct term for what we have in space that most people call "zero gravity". Gravity does diminish very fast with distance to become very negligible, but it still operates even infinitely far, so in a space station, even if the effect of the Earth, the ship and everything else in the universe is very very small, we cannot really say that the gravity is zero.

            [–]prosequare 3 points4 points ago

            The effect of gravity on the space station is in fact very strong which is why the ss moves as fast as it does. The reason that the environment inside the ss is called microgravity is that it is in a state of perpetual free-fall within the influence of a strong gravitational field.

            [–]dont_press_ctrl-W 1 point2 points ago

            Indeed. What I was describing was stationary microgravity, which is not exactly what we have in space stations. It's simpler to explain.

            [–]Tanory07 0 points1 point ago

            Fire is light so it goes up, but it not light in space, so it not go up.

            [–]Nasir742 0 points1 point ago

            Gravity = orange No gravity = blue

            [–]Owncksd 0 points1 point ago

            ELI5 has to be one of the most ingenious ideas for a subreddit ever.

            [–]Alomari31 0 points1 point ago

            This might help: http://www.reddit.com/r/explainlikeimfive/comments/uxvkh/quantum_physics_grad_student_ben_ames_wins_alan/

            load more comments (1 reply)

              [–]nextwiggin4 5 points6 points ago

              even though I knew that, I really liked reading your explanation. It's really well written, explains it simply.

              [–]ztluhcs 0 points1 point ago

              Thanks!

              [–]chidori5000 5 points6 points ago

              Tagged as The Fire Magician.

              [–]ztluhcs 4 points5 points ago

              My life is complete.

              [–]Lizardizzle 0 points1 point ago

              Tagged as Firelord Ztlugc- FUCK THIS, I CAN'T SPELL YOUR NAME.

              [–]ztluhcs 2 points3 points ago

              Last name, backwards!

              [–]Ryganwa 3 points4 points ago

              IIRC another interesting fact about lighting a candle in microgravity is that it requires more work to keep itself lit.

              In normal gravity convection carries the hot carbon dioxide up and away from the flame so that fresh oxygen feeds to the source. But in microgravity the CO2 tends to linger around, meaning the flame has a good chance to smother itself out.

              [–]McCl3lland 1 point2 points ago

              So would this burn things better or be hotter than a normal candle flame?

              [–]ztluhcs 2 points3 points ago

              I don't know about hotter, because as Ryganwa pointed out there may be more work being done in a microgravity flame (although I don't recall this fact, it seems plausible). You can definitely say that energy release in microgravity tends to be more. This is because most of the energy release from combustion comes in the final step where either the H2O or CO2 is formed. Since you don't have convection carrying away your intermediate species mid-combustion, more of them are going to make it to those final species instead of forming soot, thus releasing more energy. This is generally considered a good thing when you're burning stuff.

              [–]McCl3lland 1 point2 points ago

              Thanks! :)

              [–]verysexyelephant 2 points3 points ago

              the flame itself is hotter, as measured by it's temperature, but, to you, would 'feel' colder. The yellow glow you see is energy being radiated away from really hot soot particles in the flame (you'll feel this near a flame). In the absence of such particles, that energy can't be radiated away, and it instead keeps the product gases much hotter.

              [–]McCl3lland 0 points1 point ago

              Thank you :)

              [–][deleted] 1 point2 points ago

              That is some sexy science.

              [–]Goldilocks123 1 point2 points ago

              Interesting. Does that mean no smoke?

              [–]DOUGUOD 1 point2 points ago

              Smoke is a product of incomplete/inefficient combustion. As efficient as they claim this flame to be, I'd say no.

              [–]anamorph 1 point2 points ago

              This is obviously a sofball question...

              [–]theseekerofbacon 1 point2 points ago

              Witchcraft. Got it.

              [–]pigeon_man 1 point2 points ago

              relevant: http://www.youtube.com/watch?v=Ccoj5lhLmSQ

              [–]ztluhcs 0 points1 point ago

              lol that was awesome.

              [–]Bendrake 1 point2 points ago

              studying combustion science is about to pay off.

              Said one man ever.

              [–]ztluhcs 0 points1 point ago

              Forever alone...

              In reality it's a pretty big field consisting mostly of grown men who never quite outgrew their pyromaniac phase as a child, only to find out that studying combustion is often less exciting than actually burning things.

              https://www.combustioninstitute.org/

              [–]Bendrake 0 points1 point ago

              This was a way better reply than I was expecting, I giggled.

              [–]boblawba 1 point2 points ago

              thank you for your work to science, this was great to read

              [–]Wobbling 1 point2 points ago

              So if you blew gently on the blue flame would it create a flame trail?

              [–]ztluhcs 0 points1 point ago

              I suspect it would. Basically you just need to sap enough energy out of the blue flame that the reactions that form soot start to take over instead of the ones that make CO2. If you blew on it just right you are reintroducing the natural convection that gravity was making happen in the first picture. It'd be hard to do though.

              [–]verysexyelephant 1 point2 points ago

              they're both 'pure diffusion flames'

              [–]ztluhcs 0 points1 point ago

              You're right, in the technical sense of diffusion flames. I guess what I was trying to point out is that diffusion terms should dominate the transport equations; convection is negligible. In reality diffusion flames are non-premixed these both are diffusion flames.

              [–]Zoomerlawns 1 point2 points ago

              Damn! I was going to say the exact same thing!

              [–]greenroom628 0 points1 point ago

              But if it is in zero or micro gravity, wouldn't the heat evenly convect outward? Leaving an orange halo around the blue?

              [–]ztluhcs 0 points1 point ago

              Heat conducts yes, but there's no fuel there. Or at least, not enough fuel to burn rich enough to make soot.

              [–]greenroom628 0 points1 point ago

              Ah...so this is a picture in zero/micro-g with less atmosphere? Because if it were the same rich atmosphere as earth, but with zero-g we'd see a different effect?

              [–]ztluhcs 3 points4 points ago

              Oh sorry I used "rich" as a technical term; it deals with the ratio of how much fuel there is to the amount of air there is. Basically outside of the flame there isn't enough fuel to burn very much. On the inside of the flame there isn't enough oxygen to burn very much.

              [–]I_Cant_Logoff 0 points1 point ago

              Convection does not occur in zero gravity. In this situation, the fire would put itself out due to the lack of oxygen provided by convection.

              [–]ztluhcs 0 points1 point ago

              Diffusion can still work in this case. Temperature is well-defined regardless of body forces (gravity), there should be maxwellian velocity distributions for all species in the air. If you deplete O2 at one boundary (the flame interface) there should be a net diffusive transport towards that boundary due random molecular motion. This transport determines the size of the flame sphere in zero gravity.

              [–]I_Cant_Logoff 0 points1 point ago

              The rate of diffusion is not high enough to sustain combustion.

              [–]slashadministrator 0 points1 point ago

              Unrelated question, is the combustion in microgravity complete or is there still soot?

              Say you wanted to light a scented candle on the space station, would the combustion be complete enough to burn clean without soot or scent?

              I'm assuming the scent is due to incomplete combustion here, I could be completely off base.

              [–]ztluhcs 1 point2 points ago

              I don't really know about scented candles. I suspect they do not use soot to make the scent as it can be harmful to inhale. In the case of microgravity though I think it is fair to say that combustion is pretty much complete in the sense that most of the fuel is consumed and goes to CO2 as the final product. There might be a little soot but not enough to cause a visible glow. Sorry I can't help more.

              [–]KeithMoonForSnickers 0 points1 point ago

              I was asked during a university interview "what happens to a candle in a space ship" and they expected 17 year old me to come up with what you just said. We got there eventually but shit the bed did I need a lot of help to get there...

              [–]TheWillbilly9 0 points1 point ago

              Someone goes to Cal Berkley!

              [–]ztluhcs 0 points1 point ago

              Noooooo! Stanford forever!

              [–]vitocorneliuscooker 0 points1 point ago

              Well put. Thank you.

              [–]ztluhcs 0 points1 point ago

              Thanks!

              [–]The_Cake_Is_A_Lie 0 points1 point ago

              Now explain it like I'm Richard Feynman.

              [–][deleted] 0 points1 point ago

              I'm looking at 575 karma. Was it all worth it in the end?

              [–]TheSemiTallest 0 points1 point ago

              Thank you for basically turning this into an AMA, and teaching myself and many others fun things about fire.

              [–]ztluhcs 1 point2 points ago

              Thanks! I love talking about science. Flames are something that we've worked with and against for literally thousands and thousands of years. Even now our transportation economy makes us rely on combustion more than ever. But the truth is we still don't completely understand it. That's kinda an amazing thing when you stop and think about it!

              [–]General_Fiasco 0 points1 point ago

              Hypothetical question: If I inhaled helium in zero gravity, would it change the pitch of my voice?

              [–]ztluhcs 1 point2 points ago

              A google search lead me to the fact that since He is lighter it changes the resonant frequency of vocal chords as it goes past them (which is how we make sounds). So gravity doesn't play much of a role here and thus inhaling helium will still make you sound like a chipmunk in space.

              load more comments (1 reply)

                [–]ObliviousAmbiguity 8 points9 points ago

                CHEMILUMINESCENCE!!

                [–]he_brew 2 points3 points ago

                In this case, buoyancy-induced convection is influenced as result of the Earth's gravitational field which exerts a force upon an object as though the object were accelerating at 9.8 m/s2 towards its center of mass. Even though the candle on Earth is static, the flame is still subject to a constant -9.8 m/s2 force exerted upon it, thus there is heat loss as we observe the flame from base to tip. This is the physical mechanism behind the observable effect which ztluhcs has explained. Since this explanation covers the effect of gravity upon objects in general, I will not invoke fluid dynamics (which is where you get into the specific applied mathematics to deal with these kinds of flows, simulations of fluids, etc).

                In zero gravity there is, generally speaking, no constant acceleration or external force (aside from those in the laws of thermodynamics) exerting itself upon the flame (barring physically moving the candle itself). Thus the flame burns in a spherical shape, nearly as hot as these particular chemicals can allow it (under these circumstances) at every point upon that sphere.

                Note how the, topologically speaking, shape of the flame of the earthly candle is also a spheroid, but it is stretched, with its furtherst and coolest point (on the flame, as it were) at the tip and the very base of the flame around the wick is still burning around the maximum temperature of the wax and wick. Hence the flame is stretched as if it were being drawn downwards in a zero gravity field ~10 m/s2. This could be easily proven by experiment, or intuition.

                [–]Lord-Longbottom 2 points3 points ago

                (For us English aristocrats, I leave you this 9.8 m -> 0.0 Furlongs, 9.8 m -> 0.0 Furlongs, 10 m -> 0.0 Furlongs) - Pip pip cheerio chaps!

                [–]Call_For_Peace 0 points1 point ago

                Relevant

                Ben Ames' winning submission for Alan Aldas' (Center for Communicating Science) Prize. The metrics were based on how well one could explain a concept in simple terms. Basically the top award for ELI5.

                load more comments (7 replies)

                  [–]DevilBetweenMyToes 26 points27 points ago

                  Reminds me of that part in Event Horizon when Laurence Fishbourne explains what fire is like in zero gravity. Pretty sweet scene and an awesome ass movie.

                  [–]Riggz309 13 points14 points ago

                  "It's beautiful. It's like liquid it... slides all over everything. Comes up in waves."

                  Lies!

                  [–]Heartwork101 10 points11 points ago

                  I assume that's what would happen if a room full of flammable gas or floating liquid was ignited, so... probably no lies.

                  [–]vteckickedin 5 points6 points ago

                  Or, you know, a ship that was exploding.

                  [–]upboat_ 1 point2 points ago

                  upvotes for event horizon

                  load more comments (1 reply)

                    [–]TubaMike 11 points12 points ago

                    Related: What is a Flame? Video by Ben Amis for The Flame Challenge.

                    [–]bryanhbell 0 points1 point ago

                    Came here to post this. Happy cake day, TubaMike!

                    [–]ClosetSchmuttun 6 points7 points ago

                    So, basically now the hotter air won't rise above the colder, denser air?

                    [–]mycatiscuterthanyour 5 points6 points ago

                    It'll push out evenly. Without gravity there is no reason for the colder denser (not heavier) air to sink or the corollary less dense hotter (not lighter) air to rise.

                    [–]ClosetSchmuttun 3 points4 points ago

                    Yeah! I got it right. Now I feel good about myself!

                    [–]Spineless_John 10 points11 points ago

                    Here's a nice video explaining why the flame looks so odd.

                    I wonder where that picture was taken. It couldn't have been aboard an American spacecraft.

                    Even though this is my first time seeing this image, I am inclined to downvote because of the OP and what his name entails.

                    [–]Derigiberble 2 points3 points ago

                    NASA has been pretty interested in investigating how fire burns in microgravity, mostly to figure ou how best to extinguish it.

                    The ISS has hosted a large number of experiments on it. Perhaps the photo comes from that?

                    [–]spacebrony 4 points5 points ago

                    It couldn't have been aboard an American spacecraft.

                    This must have been one of those Russian spacecraft.

                    American spacecrafts would just have lightbulbs

                    [–]clyde_taurus 1 point2 points ago

                    NASA needs a better band.

                    Heavy metal?

                    What happened since 2001: A Space Odyssey

                    [–]jdrama83 5 points6 points ago

                    It's a mass effect field...

                    [–]cogentc 2 points3 points ago

                    This is a repost, as dictated by his user name...

                    [–]Calvinb27 2 points3 points ago

                    So if I'm ever trapped in the Antarctic, if I stop gravity I will retain more eat and survive longer? Right?

                    [–]Vanthryn 1 point2 points ago

                    No.

                    [–]alt113 2 points3 points ago

                    Username fits.

                    [–]pimpin_cowboy 2 points3 points ago

                    This might help

                    [–]freeze_inthe_breeze 5 points6 points ago

                    FYI, "zero gravity" does not exist. There is gravity everywhere in this universe.

                    [–]Malgas 6 points7 points ago

                    ...but freefall is functionally equivalent.

                    [–]DarthAardvark 0 points1 point ago

                    microgravity then

                    load more comments (1 reply)

                      [–]Baaz 1 point2 points ago

                      related:

                      http://www.youtube.com/watch?v=iSqOqRACxUM

                      [–]Squirting_Asian 1 point2 points ago

                      I see a gopher in front of a blue moon [4]

                      [–]albertojauregui 1 point2 points ago

                      Cool

                      [–]xHassassin 1 point2 points ago

                      Sustained fire can't exist in microgravity. The waste gas, co2 and water vapor, would not move away from the flame as it does on earth. The flame would basically suffocate itself shortly after being lit due to inability to get oxygen.

                      [–]atomp95 1 point2 points ago

                      i dont doubt you but in a place with 0 gravity wouldnt it have to be a vacuum, and for it to be a vacuum wouldnt that take out most of the oxygen making the fire unable to exist?

                      [–]dspadm 0 points1 point ago

                      No, the iss has essentially 0 gravity and is not a vacuum. The reason that it is a common misconception is because the most common place that 0g occurs is in outer space which is a vacuum.

                      [–]rdp3186 1 point2 points ago

                      First thing i thought off

                      "event horizon"

                      [–]Call_For_Peace 1 point2 points ago

                      Relevant

                      Ben Ames' winning submission for Alan Aldas' (Center for Communicating Science) Prize. The metrics were based on how well one could explain a concept in simple terms. Basically the top award for ELI5.

                      [–]ChewyIsThatU 1 point2 points ago

                      Just think, if there was a tiny core of nuclear material in the center causing the fire of the one in space, it would be spherical. A much larger example of that exists about 93 million miles from where you sit.

                      [–]DamnYouDamnYouAll 1 point2 points ago

                      what wicked sorcery is this?!

                      [–]JD-King 1 point2 points ago

                      I have waited so long for this pic!

                      [–]DoctorHeadshot 2 points3 points ago

                      GUESS OUTER SPACE IS KIND OF "HOT", ISN'T IT?!

                      HA? HA? HA...

                      ...I'll sit in the corner and think about what I've done...

                      [–]JohnWL 0 points1 point ago

                      That is so cool. So damn cool.

                      [–]TellMeMorePlz 0 points1 point ago

                      Ahh But how does an ignited fart behave in Zero gravity?

                      [–]cowpunter 0 points1 point ago

                      Notice how the flame stays closer to the source and is a lot more hot? Imagine that with your fart. In all likelihood you set your pants on fire.

                      [–]kragmoor 0 points1 point ago

                      RAISE THE SHIELDS

                      [–]slicer1229 0 points1 point ago

                      watch this video, it sort of explains it http://www.youtube.com/watch?v=1pfqIcSydgE

                      [–]Zzaproot 0 points1 point ago

                      Looks like a Ghost from Pac Man is mooning you.

                      [–]thisguykills 0 points1 point ago

                      It actually looks cooler in video form

                      [–]Marples 0 points1 point ago

                      r/woahdude

                      [–]samjowett 0 points1 point ago

                      This picture is misleading. The flame on the right would be very much smaller. The pictures are not to the same scale.

                      [–]professorg3 0 points1 point ago

                      Related This guy has some of the coolest videos and has taught me more than school has

                      [–]SexierInGlasses 0 points1 point ago

                      Which side is in zero gravity?

                      [–]FishWash 0 points1 point ago

                      Where could they have done this? Just wondering out of curiosity, because it would be unsafe to do it in a space shuttle or something, right?

                      [–]sta1994 0 points1 point ago

                      Wouldn't that be unsafe to do in a space shuttle

                      [–]twojake 0 points1 point ago

                      now smoke in zero gravity fuck

                      [–]LeprechaunGold 0 points1 point ago

                      OMFG!!! THIS MUST BE TRIED!!!! Epicness has been reached.

                      [–]whatsanlp 0 points1 point ago

                      its a tiny star.

                      [–]usagicanada 0 points1 point ago

                      I HAVE ALWAYS WONDERED THIS.

                      [–]fuck_your_diploma 0 points1 point ago

                      Heh

                      [–]Mdaishi 0 points1 point ago

                      • mircogravity

                      load more comments (12 replies)

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