Here on planet Earth we're used to flames -- whether from a candle or campfire -- reaching upward to the sky with slender limbs hungry for oxygen and driven by rising hot air. But in space, sans our planet's strong gravitational pull, flames are more likely to take the shape of eerie fireballs.
Within the flame of a regular candle wick, there's quite a bit going on. As the video below released this week by NASA explains, molecules from the wick are being cracked apart and vaporized by the flame, then combined with oxygen to produce light, heat, carbon dioxide, and water, as well as soot.
In recent years we've become quite familiar with how flames can extend and expand quickly in their greedy quest for more fuel and oxygen; witness countless western wildfires of the past decade. But researchers aboard the International Space Station have observed that flames in microgravity behave much differently, staying in a small spherical shape and letting oxygen molecules come to them.
They also discovered something very strange while conducting experiments on how to put out fires in their environment. Small droplets of a fuel called heptane were set aflame inside a test chamber. The flames quickly went out, but surprisingly the droplets continued to burn without the presence of flames.
It could be that flames are actually present, but just too faint to see, something NASA refers to as "cool flames."
Cool flames can burn at temperatures as low as 400 degrees Fahrenheit, but they behave very differently from the flames we're used to. For starters, they don't produce the carbon dioxide we're used to getting from fires. Instead they give off carbon monoxide and formaldehyde. Fortunately, cool flames typically can't exist on earth for more than a few fractions of a second, whereas they can persist on the International Space Station for up to a minute.
However, NASA says these insights could have practical implications on our planet, such as better fuel efficiency.
So get ready for the next generation of vehicles -- new, improved, and with more space fireballs! Watch the video below for a more eloquent explanation of the science and let us know what potential you see in formaldehyde-expelling balls of fire in the comments.