why does fire or flames burn away into those jagged/spiky shapes?

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why does fire or flames burn away into those jagged/spiky shapes?

In: Chemistry
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Flames are just glowing hot air.

flames go upward because hot air goes up, the hotter the faster it goes up. They form spikes because the hot air in contact with the colder room air gets golder and ceases to glow. so it gets thiner, and thiner overtime (which, since it moves is also above)

Short answer; gravity.

Let’s look at a match for example. After you strike the match and it’s burning away nicely there’s a few things going on. The heat is vapourising the wood which releases flammable gases. These gases combine with oxygen in the surrounding air and the heat causes a chemical reaction, producing more heat. While this is going on the gases being hotter and less dense want to go up, pushing the out of the way. The air is dragged in from the bottom to replace the consumed oxygen and is dragged along for the ride.

If you light a match in the ISS, it will burn with a spherical flame as the density differences don’t make any difference.

You can watch youtube videos showing flame experiments on the ISS. The microgravity environment results in a small blue spherical flame around the burning item. Because there is no *gravitational “down” in that scenario, there is no density preference to create an air current from changes in density.

*The ISS is in orbit, not actual zero/microgravity. Due to its orbital speed the ISS is constantly falling. Due to its velocity “sideways” the amount it falls down is either equal to or greater than the amount that the surface moves away due to the curvature of the earth. The earth’s gravitational pull at the altitude of the ISS is about 90% of what it is at the surface.

[https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html](https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.html)