In earth’s gravity, buoyant convection develops when hot, less dense combustion products rise.
Does a candle burn the same on a space station as it does on earth?
Candle flames behave differently in outer space (microgravity) than they do on earth, primarily because microgravity provides an environment that lacks buoyant convection, which normally plays an important role in maintaining and shaping a flame on earth.What is microgravity? Astronauts on the International Space Station are orbiting the earth in free fall the space station, the astronauts and everything on board are all "falling" around the earth at the same rate. This creates the floating sensation we think of as zero gravity, or more correctly, microgravity. The astronauts experience a sense of weightlessness, but it is gravity that holds the space station in its orbit.
In earth’s gravity, buoyant convection develops when hot, less dense combustion products rise. The flow that results draws cooler surrounding air to the base of the flame, supplying it with the oxidizer (in this case, oxygen) that the flame requires to maintain itself. Combustion products (carbon dioxide, water vapor, and soot) are carried away from the flame by the same convective flow, which is the dominant transport mechanism in the flame.
Candle flames on earth (left) have several different
temperatures within the flame; on a space station (right), there is no
buoyant convection, and the flame burns slower and hotter.
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