Trivia Teaser: Sticking Points

Question: True or false: The viscosity (or ‘stickiness’) of a gas actually increases with increasing temperature (unlike a liquid). So even though it becomes less dense when warmed, and its molecules move further apart and more quickly, a gas becomes, in a way, thicker at the same time that it gets thinner.

Answer: True. For aircraft at least, skin friction drag increases with increasing temperature. It is a function of an object’s velocity, its length, and the viscosity of the fluid through which it moves (or which moves by it). The best place to get more detailed information is