relativnosti

Relativity, in physics, refers to theories about space, time, and gravitation that reject the idea of an absolute space or time and emphasize that physical laws depend on the observer’s state of motion. In many languages the term is rendered as relativnost or relativnost, but the science is the same.

Two main theories form the core of modern relativity: special relativity (SR) and general relativity (GR). Special relativity, introduced by Albert Einstein in 1905, holds that the speed of light in vacuum is constant and the same for all observers in inertial frames of reference. It leads to Lorentz transformations between coordinates, time dilation, length contraction, and the relativity of simultaneity, and it implies mass–energy equivalence, E = mc². General relativity, completed in 1915, extends these ideas to gravitation by describing gravity as the curvature of spacetime caused by energy and momentum, formalized by Einstein’s field equations. It predicts gravitational time dilation, light bending, gravitational redshift, the advance of Mercury’s perihelion, and gravitational waves.

Experimental support includes measurements during solar eclipses, precision timing with atomic clocks, observations of binary pulsars, and direct detections of gravitational waves by LIGO. The theories underpin modern cosmology, black holes, and the expanding universe, and they are essential for technologies such as GPS, which require relativistic corrections for accurate positioning.

Philosophical relativity, by contrast, concerns the dependence of knowledge or truth on conventions or perspectives, and is distinct from the physical theories of relativity.