[File:Flight dynamics with text.png|right|thumb|The position of a rigid body is determined by the position of its center of mass and by its attitude (at least six parameters in total).]] In physics, a rigid body is an idealization of a solid body in which deformation is neglected. In other words, the distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it. Even though such an object cannot physically exist due to relativity, objects can normally be assumed to be perfectly rigid if they are not moving near the speed of light.