"General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics."
A theory that describes gravity as the curvature of spacetime caused by the presence of mass and energy.
Special Relativity: The theory of relativity deals with the relationship between space and time. Special relativity is a subset of relativity theory that explains how space and time are connected.
Tensor Calculus: Tensor calculus deals with the mathematics of multidimensional space-time. Einstein's theory heavily relies on the use of tensors to describe the geometry of space-time.
Manifolds: Manifolds are mathematical spaces that have more complicated structures than the usual three-dimensional space we commonly visualize. In the theory of relativity, space-time is modeled as a type of manifold.
Geodesics: Geodesics are the shortest paths between two points on a curved surface. In the context of General Relativity, the trajectories of particles under the influence of gravity are geodesics.
Curvature: The curvature of a space tells us how it deviates from a flat space. General Relativity describes gravity as the curvature of space-time caused by a massive object.
Equivalence Principle: The equivalence principle states that the effects of gravity are indistinguishable from the effects of acceleration. This leads to the idea that gravity is a result of the curvature of space-time.
Black Holes: A black hole is a region of space where the gravitational attraction is so strong that nothing, not even light, can escape from it. General Relativity predicts the existence of black holes.
Gravitational Waves: Gravitational waves are ripples in space-time caused by the acceleration of massive objects. These waves were first detected in 2015 and provide strong confirmation of General Relativity.
Cosmology: Cosmology is the study of the universe as a whole. General Relativity plays a critical role in modern cosmology, providing explanations for the Big Bang, dark energy, and the large-scale structure of the universe.
Quantum Gravity: General Relativity and quantum mechanics are the two pillars of modern physics, but they are incompatible at a fundamental level. Quantum Gravity is the attempt to combine these two theories and create a unified theory of physics.
Curved spacetime: This is the central concept of general relativity. According to the theory, the presence of mass and energy warps the fabric of spacetime, causing the geometry of the universe to be curved.
Gravitational waves: These are ripples in the fabric of spacetime that travel at the speed of light. They were predicted by general relativity and were finally observed in 2015, confirming Einstein's theory.
Black holes: General relativity predicts that extremely massive objects (such as stars) can collapse into infinitely small, infinitely dense points called black holes. These objects have extremely strong gravitational fields that can distort spacetime around them.
Time dilation: General relativity predicts that time is affected by gravity. In areas of strong gravity, time passes more slowly than in areas of weaker gravity.
Gravitational lensing: The bending of light by gravity is another prediction of general relativity. This phenomenon has been observed many times and is used to study the properties of galaxies and other massive objects.
Cosmological models: General relativity is used to study the large-scale structure of the universe and to develop models of its evolution. Some of these models predict the existence of dark matter and dark energy, which are currently the subject of intense study in astrophysics.
Tests of general relativity: Despite its overwhelming success in explaining many phenomena in the universe, general relativity is not a complete theory of gravity. It is still being tested and refined, and experiments are constantly being performed to verify its predictions and search for evidence of its limitations.
"General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime."
"In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present."
"Some predictions of general relativity, however, are beyond Newton's law of universal gravitation in classical physics."
"These predictions concern the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light, and include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the Shapiro time delay, and singularities/black holes."
"So far, all tests of general relativity have been shown to be in agreement with the theory."
"The time-dependent solutions of general relativity enable us to talk about the history of the universe and have provided the modern framework for cosmology, thus leading to the discovery of the Big Bang and cosmic microwave background radiation."
"Reconciliation of general relativity with the laws of quantum physics remains a problem, however, as there is a lack of a self-consistent theory of quantum gravity."
"Einstein's theory has astrophysical implications, including the prediction of black holes—regions of space in which space and time are distorted in such a way that nothing, not even light, can escape from them."
"Microquasars and active galactic nuclei are believed to be stellar black holes and supermassive black holes."
"It also predicts gravitational lensing, where the bending of light results in multiple images of the same distant astronomical phenomenon."
"Other predictions include the existence of gravitational waves, which have been observed directly by the physics collaboration LIGO and other observatories."
"In addition, general relativity has provided the base of cosmological models of an expanding universe."
"Widely acknowledged as a theory of extraordinary beauty, general relativity has often been described as the most beautiful of all existing physical theories."
"General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915."
"General relativity provides a unified description of gravity as a geometric property of space and time or four-dimensional spacetime."
"These predictions concern the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light, and include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the Shapiro time delay, and singularities/black holes."
"So far, all tests of general relativity have been shown to be in agreement with the theory."
"The time-dependent solutions of general relativity enable us to talk about the history of the universe and have provided the modern framework for cosmology, thus leading to the discovery of the Big Bang and cosmic microwave background radiation."
"Reconciliation of general relativity with the laws of quantum physics remains a problem, however, as there is a lack of a self-consistent theory of quantum gravity."