A new device invented by David Lentink, assistant professor of mechanical engineering at Stanford University, will answer long-held questions about the forces birds generate while flying, and could lead to the development of innovative, efficient unmanned aerial vehicles (UAVs). Lentink calls his device an aerodynamic force platform, and it works similarly to the force platforms that allow bioengineers to study the forces that humans exert to walk or run. The humane device is a box the size and shape of a large birdcage, with an acrylic observation window and two bird perches inside. Supersensitive force sensors are attached to the bottom of the box. This force transfer is based on Newton's third law of motion, which states that for every action there is an equal and opposite reaction. As the bird flies perch-to-perch, each beat of its wings pushes against the air, which in turn pushes against the bottom of the box and also sucks down the ceiling slightly. These forces are recorded to produce a precise measurement for each stroke of the bird's wings. Each wing beat lasts 50 milliseconds, and the sensors take a new measurement every 1 millisecond. A very precise value can be determined every 10 milliseconds, producing highly detailed data of the bird's lift.