r/Damnthatsinteresting • u/Brilliant-Cheek4944 • 3h ago
Image [ Removed by moderator ]
[removed] — view removed post
165
u/Ramuh321 3h ago
In a zero gravity environment with air available to have the fire burn wouldn’t there still be the updraft from the heated air? Not sure I understand why gravity causes the classic flame shape. I always thought it was the burning and heated air itself, not gravity
Edit - now that I think about it, the air with higher heat would expand in all directions without gravity since there is no gravity to pull it down. Maybe?
71
u/Ecstatic-Arachnid981 2h ago
Your edit is correct.
16
u/Financial-Week5787 1h ago edited 3m ago
convection makes combustion far more efficient. not only are the hot combustion products (like co2) are being taken away (rising away) from the reaction interface but the lower pressure sucks in cold oxygenated air from underneath.
the natural partitioning of gases occurs because colder denser gases sink and hot lighter gases rise on account of gravity.
without gravity the blob is self limiting. all the co2 and smoke just sits around the flame, as the o2 takes time to penetrate the blob. though its all relative, a slower reaction, that relies on inefficient diffusion of co2 out and o2 in gives a longer time to ensure all reagents undergo complete combustion
5
u/Mangoen123 2h ago edited 2h ago
On earth all the air pulld towards the center of the planet so we have a layering where more away from the center rhe density or pressure goes down from the air. When you heat air it wants to rise because it‘s density is less and so it wants to lie on top of denser air so in space or rather on a spaceship you don‘t have this, you have the same pressure normalized around the ship so the heated air has no prefered way to go that would be my idea how this works 😅
5
u/Happythoughtsgalore 2h ago
Air is a fluid thing. Water turns to spheres in no gravity, so too do gases (unless propelled by fans creates currents.
3
u/BrazilBazil 1h ago
There is no convection in zero gravity - the air just doesn’t mix pretty much at all. Fun fact: astronauts on the ISS have to sleep with a fan pointed at their face so that they don’t suffocate in their own CO2 bubble.
156
16
u/therock770 3h ago
Which coincidentally enough makes fire in space about 10x more dangerous. I mean think about it on Earth fire is always on something. In space you can have pockets of fire just kind of floating around.
10
u/PotatoDominatrix 2h ago
Wait until you hear about stars...
4
u/Beldizar 1h ago
Stars aren't on fire though. In fact, they'll reverse fire things. If you take some carbon, or hydrogen and burn it, it combines with oxygen to create CO2 or H2O respectively. Put that burnt product on the surface of a star, and the star's heat will reverse that reaction, breaking the carbon or hydrogen apart from the oxygen.
1
u/SalamanderGlad9053 1h ago
It means there is no convection to provide fresh oxygen, so it smothers itself quite quickly.
10
34
u/NobleNop 3h ago
Woah is that u da sun is like that?
22
15
u/Shmav 3h ago
No, the sun is like that because its absolutely massive. So massive that the nuclear fusion at its core is mostly unable to escape its gravity. The massive gravity and nuclear fusion have obtained a kind of balance where neither force can overcome the other, at least, until the sun runs out of its primary "fuel" (hydrogen).
4
u/Beldizar 1h ago
Also, the sun isn't on fire. It's actually too hot to burn. If you take hydrogen and oxygen and put them together at room temperature, then add a spark, the hydrogen will burn (chemically react with oxygen), and generate burnt-hydrogen, aka steam. Cool down burnt-hydrogen and you get water. Take water to the sun, and it heats up so hot it "unburns", with the hydrogen and oxygen splitting apart. It's so hot that you can't do the spark thing again and get them to recombine.
1
12
u/RanzigerRonny 3h ago
How does it get air?
22
u/BipedalCows 3h ago
Me (Zero gravity doesn't mean absence of air, like how you sometimes see astronauts or animals or celebrities in zero g talking/experiencing without a space suit but still breathing I think)
19
u/RanzigerRonny 3h ago
There has to be constant ventilation in space stations. Otherwise astronauts would suffocate because a bubble of carbon dioxide would form around them. That's why I was asking myself how the candle gets air.
18
u/BipedalCows 3h ago
Ahhh an astute observer and a man of knowledge eh? Well you see, the answer is that I don't know, sorry.
6
u/RanzigerRonny 3h ago
xD nah I don't have much knowledge about this. But I love space and space science. That's why I know some things. But not much. I still wonder if somebody could answer my question
4
u/BipedalCows 3h ago
Yes yes, knowing that you have much to learn is a sign of knowing plenty in itself. I'm sure there's someone out there who can answer.
9
u/Wank_A_Doodle_Doo 3h ago
There has to be constant ventilation
I feel like you kinda answered your own question there
4
u/GameThinker 2h ago
In a way yes but it might not be that simple of an answer. Some tests on the ISS are done in vacuums or containers. Easier to not make messes especially when they get sent up or back as the testing materials if the test materials are messy or toxic. What if they did this flame test in a little vacuum jar and only fed it a little oxygen to not let any go to waste?
2
u/Beldizar 1h ago
Yeah, this is accurate and a good catch. Fires like this will actually burn themselves out pretty quickly in space because there's not enough oxygen where they are, and convection can't carry new oxygen to them because it needs gravity to function. A space station is going to have ventilation, but it won't be fast or strong enough to keep up with a source of flame like this. After it burns out, people nearby have to be careful because it can leave a bubble of CO2 for a while until the ventilation and CO2 scrubbing systems can catch up.
5
u/Mirar 3h ago edited 3h ago
That's why it forms a globe, it's the surface where the oxygen is. https://www.youtube.com/watch?v=LyXqDqB3ikc
The match carries it's own oxygen, note the difference.
2
u/BoysenberryAdvanced4 2h ago edited 2h ago
If you are asking how the flame is sustained, the flame gets oxygen from all directions via diffusion, as opposed to convection currents. As the flame front consumes oxygen more oxygen diffuses from the surrounding air to the flame front. The travel of oxygen to the flame is slowed down by the CO2 diffusing away from the flame front, and vise versa. This results in a sperical flame front that is poorly fed and suffocated.
1
u/Just_Condition3516 2h ago
I‘d guess „not“. the yellow in the earth flame is the area where the sud, resulting from the first imperfect combustion (blue flame), is burnt. it had to rise to come to that reaction. for it is missing in the other flame, I suppose it burns only as the first phase and rather quickly dies out, lack of o2.
1
6
u/Leading_Screen_4216 2h ago
Do people not got to school anymore? This is GCSE physics.
3
u/PacoTaco321 Interested 39m ago
I'm going to be honest. Space fire wasn't exactly a topic that came up in high school (or really had a reason to).
2
u/crwdbull 33m ago
I humbly apologize for not remembering this random trivia piece I may have heard about 15 years ago.
4
2
u/I_Zeig_I 56m ago
It's a blob becaue yhe fuel is below and cuts off oxygen flow due to its presence.
If the fuel was centered it would be a sphere, like a star
2
1
1
1
u/cwb4ever 3h ago
if this was done on the I.S.S then its in microgravity. would microgravuty and zero gravity produce the same look/effect?
2
u/12thLevelHumanWizard 2h ago
Yes. With the exception of some relativistic time dilation from the gravity well the station is orbiting much gravity is identical to zero gravity… mostly. If you were to build a space station way out past Neptune you’d have the same flame.
1
u/Br0nnOfTheBlackwater 3h ago
I mean, isn't teardrops in zero gravity also round shape? so technically flames in zero gravity still teardrops.
1
1
u/PowCowDao 1h ago
So, you're saying that, when those billionaires want their data centers in space, the heat disposed from those centers will stay in the centers and burn up?
1
u/sprauncey_dildoes 45m ago
I’m sure they’re clever enough to design something to blow the heat away from the centre.
1
1
u/ButItWas420 55m ago
I follow this artist that makes candles with different flame colours and i want all of them
1
1
1
1
1
u/DuckWhatduckSplat 3h ago
This isn’t zero gravity. It’s microgravity. But even that is a misnomer. In earths orbit, the earths gravity is still there and still strong. Things only experience diminished effects because they’re going so fast around the earth they’re going up at the same speed they’re going down.
2
u/Lumpy_Benefit666 2h ago
Youre not going up at all when youre in orbit, youre going sideways and falling down, but youre going sideways that fast that you keep missing earth.
When you fall you cannot feel gravity, thats the weird feeling in your tummy, its weightlessness. Youre falling constantly whilst in orbit. You do not feel the effects of gravity. Youre also already at the speed youre travelling at, so you dont experience any acceleration at that angle either.
1
u/DuckWhatduckSplat 2h ago
When you’re going sideways so fast against the curvature of the earth it’s centrifugal force opposing gravity. Which is fake antigravity.
1
u/Lumpy_Benefit666 1h ago
If i were to throw a ball really far, would it experience centrifugal force as it soared through the air? No. If it were to spin through the air then it would to some degree, but the act of it flying would not.
The iss is doing the exact same thing as this, except at a much higher speed, and higher in the atmosphere. It is in freefall but is going ridiculously fast so falls around earth rather than into it. Centrifugal force is not a factor in relation to the microgravity that the iss experiences.
1
u/DuckWhatduckSplat 1h ago
My bad. I meant centripetal.
1
u/Lumpy_Benefit666 1h ago
Gravity acts as a centripetal force so it would not oppose gravity either.
There are no forces opposing gravity in microgravity, you are literally just falling the entire time
1
u/DuckWhatduckSplat 1h ago
What I am saying is… Earth’s gravity doesn’t cease to exist in space. Orbit isn’t a zero gravity or micro gravity environment, contrary to popular belief. Gravity exists but isn’t noticed due to centripetal force. I:e. Things in orbit are falling sideways, at all times under the pull of earths gravity. There should be a word that replaces microgravity as it’s a misnomer and frankly wrong.
2
u/Lumpy_Benefit666 1h ago
Yes the iss is still under the influence of earths gravity in the same way that a falling elevator is under the influence of earths gravity, yet if you were inside of either one of them, you would feel weightless. The effects of gravity are not apparent to you. Nothing is pulling you into the ground, even though you are being pulled towards earth.
Its the same as how you can be sat in bed and feel completely still and calm whilst hurtling through space at hundreds of Km a second.
We do not feel the gravity of the sun, even though the earth is locked to its gravitational field, just like the iss does not feel the earths gravity. The earth is to the sun as the iss is to the earth.
Centripetal force is not relevant in this conversation. The earth is falling towards the sun but keeps missing it, same as the iss.
Its all relative, they will feel weightless and their bodies will react the same way as if they were floating through deep space.
If you stand in an elevator and it begins to move upwards, you feel heavier. You experience “G-force”. 1 G refers to an acceleration of 9.81ms2 and you always experience 1G whilst being on earth. If the elevator accelerates upwards at 9.81ms2 then you experience 2Gs, twice earths gravity. Half of that is simulated gravity.
The iss experiences simulated microgravity. The effects are the same as if there were no gravitational pull on you
-3
1.6k
u/Mauchit_Ron 3h ago
It's because heat rises, but there is no "up" in space due to the lack of gravity caused by there being no apples in space. If there were such a thing as space apples then space would have just as much gravity as earth and the flame would look more familiar to us