apparently it’s old news, but someone recently told me about the “experiment” of lighting a candle aboard the ISS.
my first thought was: “where does the flame point?”
here on earth, flames have the shape of a teardrop. that’s because hot air is lighter (or less dense) and ascends, bringing more oxygen to the point of combustion.
take away the factor of gravity (for example, on a spacecraft) and there’s no “up” or “down”. buoyant convection can’t happen, and diffusion is the only way for oxygen to get to the flame, which results in a blue, hemispherical flame.