The title here may not be descriptive enough....I know how pitot-static systems work: difference in total pressure and static pressure yields dynamic pressure which is equal to 1/2*rho*v^2. My question is, why is it that the dial on the air speed indicator's gauge has linear markings? If I am measuring pressure to get velocity, but pressure increases with the square of the velocity, I would expect the markings on the dial to be very close together in the low range and then get gradually farther apart in the high range. Clearly, there is a mechanical system inside the gauge that handles this, but it must be more than a torsion spring system because springs have linear expansion rates (kx). What mechanically is happening inside the gauge here?