Why does a candle always point up and not sideways , in the sense that why is it always it the shape is why not circle or square and stuff.
In a word: convection. Air gets heated by the flame and rises, pushing up the flame. If you were to light a candle on the Space Shuttle the flame would be a sphere. (It would then extinguish itself, because the used up air cannot go “up” and stays around to suffocate the flame.)
If you pointed it sideways, the wax would drip on the floor before it could burn. If the candle is pointed straight up, the wax pools and is sucked up the wick by capillary attraction and burned.
Actually, they have gotten candles to light in space, and not extinguish themselves. It’s pretty amazing. The light is in a big, cool-looking sphere, due to the lack of convection.
Of course, if you accidentally set something on fire in the space shuttle, you’re pretty screwed. The smoke doesn’t “rise” and you can’t drop to the “floor” to get into a safe spot. You just have to dash to the extinguisher as fast as possible and get some kind of reserve oxygen supply.
The Master has considered this issue: If you lit a flame in zero gravity, would it smother in its own smoke?