RE: The Pecular Behavior of Fire
December 10, 2016 at 8:17 am
(This post was last modified: December 10, 2016 at 9:43 am by Anomalocaris.)
(December 9, 2016 at 7:52 am)chimp3 Wrote: Fire is plasma
Not any fire you can easily light.
(November 17, 2016 at 5:57 pm)Rhondazvous Wrote: Fire gives off light but does not act like light.
If you light a torch and hold it aloft the fire will shoot upward. But if you hold the torch horizontally, the fire will still shoot upward. Whereas if you hold source of light, such as a flash light, horizontally the light will continue horizontally.
No matter how far fire spreads it maintains its triangular shape, sometimes producing several triangles with one angel pointing upwards, unless it encounters a downward facing surface such as a ceiling. Then the fire spreads along the surface and that surface becomes it's base. It resumes its triangular shape when it eats through the surface to the air above.
Is there a scientific theory of fire that accounts for this behavior?
Fire is the process of rapid exothermic oxidation chemical reaction. What you are describing is flame, which is hot incandescent gas emitted by fire. Light is not an intrinsic product of the reaction. Rather light comes from incandescent radiation associated with any hot object, including the flame. Flame gives off light for the same reason the filament in a traditional incandescent light bulb gives off light when an electric current heats the filament.
Hot gas is less dense than cold atmosphere. Flame typically starts out only 1/3 or 1/4 as dense as atmosphere. So flame is highly buoyant and floats up rapidly. However, as the flame rises, it both cool by radiating away some of its heat, and by mixing with cool surrounding air. When cooled sufficiently, it stops giving off visible light. The edges cools the quickest, as it entrained cool air as it rises right from the beginning, and therefore rises the least before stopping to give off light. The center part of the flame is the part most protected from cool surrounding air, as a result it remains hot and incandescent the longest, and floats up the most, before it too eventually stops giving off light. This differential cooling rate between center and edge of flame is what gives it its triangular shape.
