Despite the simple appearance of the boomerang, the characteristic returning flight is guided by a complex combination of physics and aerodynamics. The returning boomerang is most commonly two wings jointed at angle between 80° and 120°, however, some newer boomerangs have more than two wings. The combination of spin and forward motion create an uneven lift over the wings. As the air flow passes over one wing faster than the other lift is created. When thrown correctly, boomerangs will return. The natural spin of the boomerang twists at right angles, which results in the boomerang's curving flight. Since the center of lift is forward of the center of gravity another tipping force is created, making the boomerang lie down during its flight. The combination of these spinning forces is called gyroscopic precession.