What do you mean direction of oxygen?cpt.fass1 wrote:
That's cool and I"m bookmarking it. But I would have to say that it burns like that because it doesn't have any direction of oxygen..
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Vacuum?! The fire tetrahedron( ya its not a triangle any more, i know i am a firefighter) states that you need and oxidizing agent, a reducing agent, heat, and a self-sustaining chain reaction. In a vacuum there would be no oxidizing agent (such as oxygen) so the flame would not exist.DoctorFruitloop wrote:
2nd law of thermodynamics should still apply even if there is little gravity. The flow of heat is still gonna be from hot to cold so the flame will spread out.Snipe=UKLF= wrote:
Yeah thats pretty much what i first thought..Bertster7 wrote:
I'd imagine it's to do with the blue part of the flame being the hottest part of it. Without gravity the flame would be centered around a smaller point, the heat wouldn't rise because there wouldn't be an up. The same amount of calorific energy would be produced from the flame, in a smaller area, so it would be hotter and therefore blue.
But then i started thinking, if theres no up then obviously heat can't rise so would the heat remain in the flame and just get hotter and hotter eventually turning white or something?
Do you know if this experiment was carried out in a vacuum with a sefl sustaining combustion source? It looks as if there's no convection goin on at all.
You do realise energy cant be created or destroyed right?Bertster7 wrote:
I'd imagine it's to do with the blue part of the flame being the hottest part of it. Without gravity the flame would be centered around a smaller point, the heat wouldn't rise because there wouldn't be an up. The same amount of calorific energy would be produced from the flame, in a smaller area, so it would be hotter and therefore blue.
Yeah, thats the second law of thermodynamics. Never destroyed just becomes more disorganized, ENTROPY.Mong0ose wrote:
You do realise energy cant be created or destroyed right?Bertster7 wrote:
I'd imagine it's to do with the blue part of the flame being the hottest part of it. Without gravity the flame would be centered around a smaller point, the heat wouldn't rise because there wouldn't be an up. The same amount of calorific energy would be produced from the flame, in a smaller area, so it would be hotter and therefore blue.
Of course I do. The energy given off is from the chemical energy in the candle being burnt which converts it into heat and light. It's basic physics.Mong0ose wrote:
You do realise energy cant be created or destroyed right?Bertster7 wrote:
I'd imagine it's to do with the blue part of the flame being the hottest part of it. Without gravity the flame would be centered around a smaller point, the heat wouldn't rise because there wouldn't be an up. The same amount of calorific energy would be produced from the flame, in a smaller area, so it would be hotter and therefore blue.
The energy given off will be uniformly distributed since there is no gravity. As a sphere the flame will be more compact and therefore all the flame will be blue, because it's hotter. In a normal candle flame only the core is blue because the the heat from the flame rises.
I haven't explained it very well, but it's quite simple really. No great mystery.
An interesting little trick you can do with a candle is to snuff it out, then light the smoke given off above the candle. Because of the combustible residues in the smoke, the flame will travel down the smoke and re-ignite the candle.
Absolutely. I can't remember it exactly, but put simply: Within a closed system (very important - that's the bit creationists leave out of all there calculations, which makes them all meanless crap), the system will tend towards entropy as time progresses.SnobbyBoss wrote:
Yeah, thats the second law of thermodynamics. Never destroyed just becomes more disorganized, ENTROPY.Mong0ose wrote:
You do realise energy cant be created or destroyed right?Bertster7 wrote:
I'd imagine it's to do with the blue part of the flame being the hottest part of it. Without gravity the flame would be centered around a smaller point, the heat wouldn't rise because there wouldn't be an up. The same amount of calorific energy would be produced from the flame, in a smaller area, so it would be hotter and therefore blue.
A simple example would be a box full of gas. The box is our closed system. If you move all of the gas into one half of the box (an ordered state) and then close the box, the gas will spread out into a more chaotic state. That is the 2nd law at work.
The 1st law is that you can't get 100% efficiency from any system. Which is more closely linked in with the conservation of energy than the 2nd law if you ask me.
Amazing. Thanks a bunch, very satisfied with the quote you gave me. Maybe I'll rent that documentary, tooBertster7 wrote:
There's a documentary called Nukes in Space which shows this sort of stuff. It's a sequel to Trinity and Beyond, another quite interesting documentary. They look quite pretty.Spearhead wrote:
A related question.....
What does an explosion look like in the vacuum of space? Unprotected, just blown up, boom. I know there can't be any fire, but what exactly would it look like? Does anyone know?
And to think.... Star Wars has been wrong this whole time.
Got this off some website, not sure on accuracy, but it sounds believable.In space, the first few milliseconds proceed as they would in air (say), but then the transfer of energy to the surrounding air never takes place. As a result the initial small, intensely hot fireball simply keeps expanding at very high speed, and the expanding gases and any fragments fly off in straight lines. The fireball cools by radiation at first, but as its density drops it becomes so transparent that radiation is suppressed. For a chemical high explosive, the expansion speed would be a few thousand feet per second. So for a moderate size explosive -- say 1 meter across -- the products will expand to 100 meters in probably less than 0.1 sec, meaning the density will have decreased by a factor of a million, and the visible explosion will effectively be over. Visually the effect would be of a very brief, brilliant flash in a region only a little bigger than the actual extent of the explosive material. Of course there would be no billowing swirling smoke, and any fragments would almost certainly be moving too fast to be visible. The effect would probably be something like that of a big flashbulb.
For a nuclear explosion, the fireball would radiate mainly in the x-ray and ultraviolet, which are not visible to the eye, although the visible part of the radiation would produce a blue-white flash. The expansion speed would be many hundreds or thousands of times faster than for a chemical explosion, so that the time scale would be less than a millisecond. All the material near the source would be vaporized, so there would be no fragments. If the explosion was truly in space, and not in a tenuous atmosphere, then viewed from a survivable distance the effect would probably be similar to, but even less spectacular than, a chemical explosion.
Last edited by Spearhead (2006-10-11 14:15:27)
Anyone have any links/pics/vids on explosions in a vacuum.. thats could be good!
Cheers for all the posts, a lot of interesting stuff!.. makes my day at work go a bit quicker
Karma on its way.
Cheers for all the posts, a lot of interesting stuff!.. makes my day at work go a bit quicker
Karma on its way.
Would there be sound in space?
Sound doesn't depend on oxygen, it depends on there being molecules. And there are molecules in space no?
Sound doesn't depend on oxygen, it depends on there being molecules. And there are molecules in space no?
Theres no sound in space mate, its a vacuum, maybe not a perfect vacuum but the matter is so sparse sound cannot travel.
The oxidizing agent could be incorporated into the make up of the candle. I'm pretty sure that divers have equipment that will burn under water without a ready supply of free oxygen, ie. air.[TFT]Hostage wrote:
Vacuum?! The fire tetrahedron( ya its not a triangle any more, i know i am a firefighter) states that you need and oxidizing agent, a reducing agent, heat, and a self-sustaining chain reaction. In a vacuum there would be no oxidizing agent (such as oxygen) so the flame would not exist.DoctorFruitloop wrote:
2nd law of thermodynamics should still apply even if there is little gravity. The flow of heat is still gonna be from hot to cold so the flame will spread out.Snipe=UKLF= wrote:
Yeah thats pretty much what i first thought..
But then i started thinking, if theres no up then obviously heat can't rise so would the heat remain in the flame and just get hotter and hotter eventually turning white or something?
Do you know if this experiment was carried out in a vacuum with a sefl sustaining combustion source? It looks as if there's no convection goin on at all.
They do. Torpedoes also have to use oxidizing agents for the engines to drive their propellers. It was a problem with one of those oxidizing agents that led to the sinking of the Kursk (is sinking the right word for a submarine?).DoctorFruitloop wrote:
The oxidizing agent could be incorporated into the make up of the candle. I'm pretty sure that divers have equipment that will burn under water without a ready supply of free oxygen, ie. air.[TFT]Hostage wrote:
Vacuum?! The fire tetrahedron( ya its not a triangle any more, i know i am a firefighter) states that you need and oxidizing agent, a reducing agent, heat, and a self-sustaining chain reaction. In a vacuum there would be no oxidizing agent (such as oxygen) so the flame would not exist.DoctorFruitloop wrote:
2nd law of thermodynamics should still apply even if there is little gravity. The flow of heat is still gonna be from hot to cold so the flame will spread out.
Do you know if this experiment was carried out in a vacuum with a sefl sustaining combustion source? It looks as if there's no convection goin on at all.
I don't think it would work very well in candle form though.
In the case of an explosion, assuming it was outside and you were in a spacecraft, you'd possible be able to hear something, but not in the same way as a typical explosion. In an atmosphere the sound of an explosion is a pressure wave being transmitted by the molecules of gas in the air. In space, no molecules = no sound wave being created that way.Vub wrote:
Would there be sound in space?
Sound doesn't depend on oxygen, it depends on there being molecules. And there are molecules in space no?
BUT, the actual gas molecules formed as the explosive went off will shoot away from the explosion. In an atmosphere they collide with the surrounding air molecules and don't go that far. In space, as there's no air in the way, these created gas molecules are free to impact the walls of your spacecraft which will deform the wall slightly (due to the sudden pressure change) and then spring back causing the creation of a pressure wave (sound) in the atmosphere inside the ship, which I assume you'd hear. Assuming the `volume` of this effect depends on how many gas molecules hit your spaceship the sound will trail off at rate of 1/r^3. so if you go twice as far away the explosion sound will be 1/8 as loud.
Also this `sound` (assuming you can hear it) will travel about the same speed as sound in a solid, faster than the speed of sound in air.
Last edited by .:XDR:.PureFodder (2006-10-12 08:02:46)
That all sounds quite plausible..:XDR:.PureFodder wrote:
In the case of an explosion, assuming it was outside and you were in a spacecraft, you'd possible be able to hear something, but not in the same way as a typical explosion. In an atmosphere the sound of an explosion is a pressure wave being transmitted by the molecules of gas in the air. In space, no molecules = no sound wave being created that way.Vub wrote:
Would there be sound in space?
Sound doesn't depend on oxygen, it depends on there being molecules. And there are molecules in space no?
BUT, the actual gas molecules formed as the explosive went off will shoot away from the explosion. In an atmosphere they collide with the surrounding air molecules and don't go that far. In space, as there's no air in the way, these created gas molecules are free to impact the walls of your spacecraft which will deform the wall slightly (due to the sudden pressure change) and then spring back causing the creation of a pressure wave (sound) in the atmosphere inside the ship, which I assume you'd hear. Assuming the `volume` of this effect depends on how many gas molecules hit your spaceship the sound will trail off at rate of 1/r^3. so if you go twice as far away the explosion sound will be 1/8 as loud.
Also this `sound` (assuming you can hear it) will travel about the same speed as sound in a solid, faster than the speed of sound in air.
The explosion itself wouldn't make any noise though, because the molecular density in space is too low. What you might hear, as you pointed out, would be some kind of debris colliding with a spaceship you were in. A bit like an explosion going off on Earth and making no bang, but debris thrown out of the explosion making noise as it hits a vehicle you were in.
I would agree that the sound would travel at the same speed as through a solid, but only once it has reached the solid (spaceship). Until that point it would be travelling at a rate determined by the force of the explosion (a=F/m) and the time the force acts on the gas molecules for, as the force would probably change throughout the very brief time of the explosion an integral calculation would be best suited to work it out exactly.
there can be fire in space so long as the exploding object provides it's own oxidizer/fuel mix, and there are a few materials that can burn without oxygen, like magnesium
and yes, sound depends on matter for transmission, so long as the molecules are touching each other to transfer the energy, generally in space the matter molecules are too far apart to effectively transfer their energy, general rule, the denser the better, if you listen submerged in nonturbulent water, you can listen to conversations many yards away from fellow swimmers, or you can hear a train coming from miles away if you put your ear or skull (the bone transfers vibration better in this case) directly to the steel tracks, so you could possibly hear it once the shockwave/shrapnel reached you or your craft
and yes, sound depends on matter for transmission, so long as the molecules are touching each other to transfer the energy, generally in space the matter molecules are too far apart to effectively transfer their energy, general rule, the denser the better, if you listen submerged in nonturbulent water, you can listen to conversations many yards away from fellow swimmers, or you can hear a train coming from miles away if you put your ear or skull (the bone transfers vibration better in this case) directly to the steel tracks, so you could possibly hear it once the shockwave/shrapnel reached you or your craft
To add to krackers post, in the movie Hidalgo, he sticks a knife into the sand in the desert and he can hear or feel the bad guys coming for him. Not sure if many people know about that. But I'm assuming that can happen in RL.
energy is not a function of gravity per se, but the heat would be. Hot air rises because it is less dense than colder air. The density is a factor on earth as gravity has less or more mass to affect respectively. As the flame is in free fall, the spent fuel is uniformly expelled away and not there to impede the burning of the flame. It is a relative sphere for the same reason.
yeah, done it myself, it's an old scout trick, more than a few people used it around here in the civil war, in fact i was shown that by a civil war historian, sure it's been around for centuries though, i even do that with long screwdrivers to locate knocking valves and such when working on carsSpearhead wrote:
To add to krackers post, in the movie Hidalgo, he sticks a knife into the sand in the desert and he can hear or feel the bad guys coming for him. Not sure if many people know about that. But I'm assuming that can happen in RL.
i need a poo
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