Special Theory of Relativity

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Relativistic Mechanics of a Particle. Collisions and Conservation Laws

The theory of relativity does not permit the existence of rigid bodies and the argument goes as follows. A rigid body is defined as a body which is non-deformable under all conditions of rest and motion. Suppose a rigid body is set into motion by applying a force from outside. The particle at the point of application will acquire the motion imparted instantly whereas the rest of the particles which constitute the body will be set into motion eventually, depending upon the velocity of propagation of the impressed interaction. Since the latter has finite velocity, there is bound to be a time lag in the different parts to acquire the motion and this is sure to cause deformation ...