# Relativistic Effect

*The Great Soviet Encyclopedia*(1979). It might be outdated or ideologically biased.

## Relativistic Effect

Physical phenomena observed when the speeds of bodies or particles ν are comparable with the speed of light *c* are referred to as relativistic effects. Examples of relativistic effects considered in the special theory of relativity are the relativistic contraction of the longitudinal (in the direction of motion) length *s*, the relativistic dilatation of time, and the increase in mass of a body as the body’s energy increases. For systems of particles, such as atoms and atomic nuclei, where the rotative motion of the particles occurs at speeds ν ≪ *c*, relativistic effects shift energy levels in proportion to the powers of the ratio *v/c*. Effects of the general theory of relativity, or the relativistic theory of gravitation, are also said to be relativistic. An example is the slowing of clocks in a strong gravitational field.