General relativity is a theory of gravity proposed by [[Albert Einstein]] in 1915, which describes the gravitational force as a curvature of space and time caused by mass and energy. It is a fundamental theory in physics that provides a framework for understanding the behavior of objects in the presence of gravitational fields. According to general relativity, mass and energy cause spacetime to curve, and objects move along the shortest path (geodesic) in this curved spacetime. The curvature of spacetime is determined by the distribution of mass and energy, creating what we perceive as gravity. This is different from Isaac Newton's theory of gravity, which described it as a force acting instantaneously at a distance. General relativity has been extensively tested and confirmed through various experiments and observations. Some key predictions of general relativity include the bending of light around massive objects (gravitational lensing), the existence of black holes, and the expansion of the universe. One important aspect of general relativity is its mathematical formulation using tensor calculus. The equations of general relativity are known as Einstein's field equations, which relate the curvature (represented by the metric tensor) to the distribution of matter and energy (represented by the stress-energy tensor). General relativity has had numerous practical applications beyond its theoretical significance. For example, it has been essential for understanding phenomena such as gravitational waves (ripples in spacetime caused by accelerated masses), which were directly detected for the first time in 2015. # The differences between general and special relativity General relativity and [[special relativity]] are both branches of Einstein's [[theory of relativity]], but they differ in several key aspects: 1. Scope: Special relativity deals with the behavior of objects in the absence of gravitational fields, while general relativity extends this to include the effects of gravity on the fabric of spacetime itself. 2. Frames of Reference: Special relativity is based on the concept of inertial frames of reference, which are non-accelerating frames. General relativity allows for accelerating frames and considers all reference frames, including those experiencing gravity. 3. Equations: Special relativity is based on a set of equations known as Lorentz transformations, which describe how measurements change when observed from different inertial frames. General relativity introduces a more complex set of equations called Einstein's field equations, which describe how matter and energy curve spacetime and how curved spacetime affects the motion of matter and energy. 4. Gravitational Effects: Special relativity does not account for gravity explicitly; it treats gravity as a force acting on objects. General relativity, on the other hand, explains gravity as the curvature of spacetime caused by mass and energy. It describes how objects move in curved space under the influence of gravitational fields. 5. Black Holes: General relativity predicts the existence and properties of black holes – regions where matter has collapsed under its own gravitational pull to form an infinitely dense singularity surrounded by an event horizon. Special relativity does not account for these extreme phenomena. Overall, special relativity provides a framework for understanding space and time in the absence of gravity, while general relativity extends this understanding to include gravitational effects and provides a more complete description of our universe. General relativity provides a comprehensive framework for understanding gravity as a curvature of spacetime caused by mass and energy. Its predictions have been confirmed through experiments and observations, making it one of the most successful theories in physics. # References ```dataview Table title as Title, authors as Authors where contains(subject, "General Relativity") sort title, authors, modified ```