Relativity

Relativity is a theory developed by Albert Einstein that transformed our understanding of space, time and gravity. It consists of two related theories: special relativity, published in 1905, and general relativity, introduced in 1915. Special relativity describes how space and time are linked and shows that the speed of light in a vacuum is the same for all observers.

As a result, time can pass at different rates for observers moving at different speeds, and lengths can appear shortened in the direction of motion at extremely high speeds. These effects are far too small to notice in everyday life but become important for objects travelling close to the speed of light.

General relativity extends these ideas by explaining gravity as the curvature of space-time caused by mass and energy, rather than as a force acting at a distance. According to this theory, planets follow curved paths around the Sun because they move through curved space-time.

General relativity has been confirmed by many observations, including the bending of light near massive objects, the detection of gravitational waves and the precise motion of planets. It is also essential for technologies such as the Global Positioning System (GPS), whose satellite clocks must be corrected for relativistic effects to provide accurate positions. Relativity remains one of the foundations of modern physics and our understanding of the universe.