2) Candles In Zero Gravity

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If you light a candle in space it doesn’t behave like you might expect. I imagined a flame in zero gravity would be sparking and flaring in all directions, like in a standard sci-fi disaster film. I was wrong. If you light a candle in space it burns as a small blue globe. Weird, huh?

The flame burns with a lot less heat and virtually no soot. Here’s one burning on the Mir space station:

But why? On earth as fire burns, it heats up the air around it and steals its oxygen. The hot air is less dense and rises up making room for new colder, oxygen rich air to be pulled into place by gravity. This colder denser oxygen rich air is then robbed of its oxygen, gets hotter and therefore less dense, drifts upwards and the cycle repeats.

Basically, if there’s no gravity the hot, oxygen poor air just stays right by the flame making it crap.