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We know what the flame of a candle looks like on Earth in 1g and what it looks like in weightlessness. But do we have an idea of what it would look like in Lunar (0.166 g) or Martian (0.38 g) gravity? Did the Apollo astronauts ignite one on the Moon or someone during a parabolic flight? Would the flame look closer to the one in weightlessness or more like on Earth?

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There has been some research on flames in 0.38g (using parabolic flights). There are no usable photos in that paper, but:

Cool flames at 0.3g appear qualitatively similar to those at 1g, yet those at μg are radially (presumably spherically) symmetric.

Which is more or less as expected. When you have gravity, you get convection (hot air rising). The speed of convection may be lower, so you get less oxygen transported toward the flame, leading to a lower flame.

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  • $\begingroup$ I'm going to guess, then, that the shape goes continuously from sphere to flame as gravity increases, and at greater than 1 g the flame gets taller and skinnier. $\endgroup$ – Greg May 11 at 12:46
  • $\begingroup$ Thank you! They only write of 0.3g but that means that at 0.38g the flame must look even more Earth-like. But it's like Greg is saying: there must be a flowing border between a sphere-like blue flame and a peaked firered flame. So I'm curious whether on the Moon a flame would look similar like on Earth and Mars or more spherical. $\endgroup$ – User31481 May 11 at 14:34
  • $\begingroup$ That's interesting... Does that mean that fires might be self-extinguishing? $\endgroup$ – Chris B. Behrens May 11 at 17:15
  • $\begingroup$ more like they'll smoulder along for a long time and will flare up at the first gust of wind. $\endgroup$ – Hobbes May 11 at 17:22

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