a, A whisker (red) of length L rotates through an angle θ against an object at distance d, which elicits a moment M at the base. b, Extraction of information about an object shape using an artificial whisker array (whisker lengths are 2, 3, 4 and 5 cm). c, Fluid-flow profiles, determined using two opposing whisker arrays, arranged as shown in the inset. V is the fluid velocity and each whisker is 0.5 cm×11 cm. Blue curve: data from whisker array; red: data from a Pitot tube placed at the height of each whisker, which gives the true air speed. Standard deviations (10 trials) are within the size of the symbols.