The theory of relativity usually encompasses two interrelated theories by Albert Einstein: Special Relativity and General Relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.
In physics, the Special theory of Relativity, or Special Relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein’s original treatment, the theory is based on two postulates:
- The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration).
- The speed of light in vacuum is the same for all observers, regardless of the motion of the light source or observer.