Relativistic dynamics refers to a combination of
relativistic and
quantum concepts to describe the relationships between the motion and properties of a relativistic system and the forces acting on the system. What distinguishes relativistic dynamics from other physical theories is the use of an
invariant scalar evolution parameter to monitor the historical evolution of
space-time events. In a scale-invariant theory, the strength of particle interactions does not depend on the energy of the particles involved. Twentieth century experiments showed that the physical description of
microscopic and submicroscopic objects moving at or near the
speed of light raised questions about such fundamental concepts as space, time, mass, and energy. The theoretical description of the physical phenomena required the integration of concepts from relativity and
quantum theory.