all know how fire behaves in space: It does not. All those action movies are wrong. The fire needs oxygen, and oxygen is not abundant outside the earth's atmosphere. Fire can occur within a closed environment and oxygenated in space, but do not behave the same way as they do on Earth. The Earth's gravity imposes many conditions on the fire, which do not exist in microgravity or zero-g. For this is why astronauts can not light a candle at both ends. [Pun on the real meaning of burn a candle at Both ENDS, and meaning as much cliché working late nights]
Gravity is a compendium of good and bad. Yes, it helps maintain muscle tone and bone density, and allows us to eat the soup in a bowl without causing a mess. Unfortunately, it also tries to kill us, making us stumble and pulling heavy objects on us. Apparently not content with beating with hard objects, gravity also trying to kill us by the fire. When a fire starts, warms the surrounding air. This causes that particular section of air becomes less dense. This section less dense air is directed upwards because gravity is pulling everything, and sections of cold, dense air displaces up on their way to a position closer to the ground. The fire is in luck, because the only reason for the hot air is because the fire was consuming oxygen. When the thin air is pushed upward by oxygen-rich air, the fire gets a new shipment of fresh oxygen to burn.
This does not happen in zero gravity. The air is heated by the fire expands, but as there is no gravity to pull the denser air into this space, just ... stays there. Meanwhile, the fire continues to consume oxygen and returning carbon dioxide until it suffocates itself. Space travel is very complicated, with many problems taking drastic consequences, fire is one of the few ways in which the astronauts have a break. Unless there is some kind of airflow feeding the fire, giving fresh oxygen, a fire in a spacecraft will turn itself off. This is not the same as saying not have to be careful with fire.
Some flames, eg candles, also change color in space. When the wick of a candle burns, is being undone molecule by molecule. This separation absorbs heat. However, when molecules, in this case, long chains of carbon, are pushed upward, as coal burning and shining with yellow. In zero gravity, the carbon chains are not consumed, and the flame is blue, cooler and more tenuous.
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