This also means that blowing out candles in space is four times easier than on Earth — a finding that more than justifies the Shuttle flights.
Here is the explanation from some smart people:
[A] candle can burn in zero gravity. However, the flame is quite a bit different. Fire behaves differently in space and microgravity than on Earth.
A microgravity flame forms a sphere surrounding the wick. Diffusion feeds the flame with oxygen and allows carbon dioxide to move away from the point of combustion, so the rate of burning is slowed. The flame of a candle burned in microgravity is an almost invisible blue color (video cameras on Mir could not detect the blue color). Experiments on Skylab and Mir indicate the temperature of the flame is too low for the yellow color seen on Earth.