But before you read the rest of the post, you should watch this video:
So, what is that, exactly? What is that glowing blue ball? Surprisingly enough, it's actually the flame surrounding a lit droplet of fuel. The reason why it looks so bizarre - and unlike any flame you're probably ever seen before - is because that's what fire looks like in a microgravity scenario.
FLEX, or the Flame Extinguishment Experiment, is an experiment that was performed on the International Space Station (ISS) to observe the results of microgravity of flame, and to determine ways that could be used to extinguish these flames (hence the name). I wrote a report on this phenomenon for my most recent module for WISH, and although it's not directly related to aeronautical engineering, it's still pretty amazing.
Why does the flame look like this? The easiest explanation is that the Earth's gravity gives an Earth-based flame a sort of teardrop shape (like on a birthday candle). However, since the ISS operates in a microgravity environment, the effects of gravity on the flame are essentially nonexistent, and the flame can expand in all directions instead of just upward. The flame also burns more slowly than a fire on Earth would. In addition to the spherical flame, the ISS scientists have actually discovered another phenomenon, called "cool flame". In some of the several hundred experiments they've performed, the droplet of fuel has continued to decrease in size even after the flame has stopped burning - as if the droplet is still lit. While the theories behind the idea of cool flame are still fairly rudimentary, it's definitely an interesting aspect of microgravity combustion.
As for the reddish glow several second after the flame goes out in the video? I'm still not entirely sure what that is. I haven't found any solid explanation for it, but I do know that it isn't cool flame. (Actually, I did find one explanation once, but it was extremely vague and seemed to be generally regarded as inaccurate, so from my perspective, the glow is still unexplained.)
Maybe it's just me, but I thought that the effects of microgravity on a flame are really pretty interesting. Wouldn't it be cool if all fires were globes (ignoring the fact that fires are damaging enough as is, of course!)?
And to continue the idea of flame:
Eternity
Will you come with me to search for eternity?
Will you peek behind doors, duck into corners,
strike match after match to light up the darkness?
Will you help me tear down the thin boundaries
between reality and impossibility, help me open the world
to a new vortex of opportunities? And if we finally find it,
will you leave me behind in a corner, in the dark
without a candle or a match, or will you stay with me
by my side through life and through death,
through this newfound land of eternity?
~Becky Hill