Naked Science Forum
General Science => General Science => Topic started by: rakarthxii on 17/11/2005 22:53:04
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Hi everyone, I'm new to all this forum do-hikkie stuff but I have a question:
If you are in a spaceship with a good supply of oxygen and light a match - what happens?
I was trying to think it through, and at first I guessed that it would simply go out, as there is no gravity so it will use up the oxygen in its vicinity and expire.
But it could be possible that the match burns if the CO2 formed has enough energy to move out of the vivinity, or through diffusion.
So any idea if it this would happen and if so, what shape the flame would be?
He who laughs last thinks slowest
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I believe this has been done and produces a spherical very slow burning flame it burns very slowly because the oxygen has to diffuse into the flame.
http://science.nasa.gov/headlines/y2000/ast12may_1.htm
has a picture
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The flame will go out.
In an environment with gravity, waste gases are taken away from the flame. Gravity pulls the heavier gases down which enables other gases to rise. In space, however, where there is no gravity, the waste gases remain around the flame & extinguish it
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The waste gases sink due to gravity?
I thought they initially rise due to being hotter/lighter than the surrounding gas. Otherwise, wouldn't the flames burn downward instead of upward?
Prediction is difficult, especially the future. -Niels Bohr
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Bass - if gravity didn't pull some of the gases down, others couldn't be lighter so they wouldn't rise away from the flame
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If you look at the link I gave you NASA has done experiments on this (they want to know what happens if their space ships catch fire) and you can still get flames, as the gasses can move in and out by diffusion so they burn very slowly.
Apparently fire detectors are really dificult in no gravity too, because you can't put them at the top of the building...
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Good point about detectors. I hadn't thought about that
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The flame - as shown from the link would not go out, although heavier gases are pulled down by gravity, the heated gas will have enough energy to rise against gravity. As that excess energy is spread to the surroundings the heavy gas will fall again. If this was not the case then flames would burn downwards!
What I find interesting, looking at the image on the link:
http://science.nasa.gov/headlines/y2000/ast12may_1.htm
is that the flame is blue!
I know the reason for this is that the electrons in the heated particles become excited and as they fall from an excited state to the ground state they release a photon of a certain frequency. That certain frequency (assuming that the photon is travelling at the speed of light) will give a specific wavelength; in this case blue light. Because the flame is blue, it shows that the gas heated in microgravity has a greater energy than the gas heated in normal gravity - why is this?
The reasons that comes to mind is that the gas his heated at a greater temperature, or the candle at microgravity is in a higher pressure surroundings. What do we reckon?
He who laughs last thinks slowest
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A normal flame is yellow because you get little particles of carbon soot which will glow yellow, these particles of carbon are there because the fuel is dragged out of the flame faster than it can burn completely, in space convection isn't doing this so it burns completely and therefore blue.
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I suggest you have a word with Dr Chris because this topic was on the radio show & they said the flame would go out