General relativity (GR) is a theory of gravitation published by Albert Einstein in 1915. It describes gravity not as a force acting at a distance - as in Newtonian mechanics - but as a geometric property of spacetime: the curvature of a four-dimensional continuum caused by the presence of mass and energy. Objects in free fall follow paths called geodesics, which are the straightest possible paths through curved spacetime. General relativity subsumes Newtonian gravity as a limiting case and makes predictions that depart significantly from Newtonian mechanics in strong gravitational fields or at high velocities.

The central insight of general relativity is that mass and energy warp the geometry of spacetime, and that this warping is what we experience as gravity. A convenient shorthand is: matter tells spacetime how to curve; spacetime tells matter how to move. Einstein's field equations - a system of ten coupled, nonlinear partial differential equations - relate the curvature of spacetime (expressed through the Einstein tensor) to the distribution of mass and energy (expressed through the stress-energy tensor).

General relativity predicts several phenomena with no counterpart in Newtonian gravity:

• Gravitational time dilation - clocks run slower in stronger gravitational fields.
• Gravitational lensing - light follows curved paths near massive objects, bending and distorting images of background sources.
• Gravitational redshift - light loses energy climbing out of a gravitational well, shifting to longer wavelengths.
• Frame dragging - a rotating mass drags spacetime around it (Lense-Thirring effect).
• Gravitational waves - accelerating masses radiate ripples in spacetime curvature, propagating at the speed of light.
• Black holes - regions where spacetime curvature becomes extreme enough that nothing, including light, can escape past the event horizon.
• Cosmological expansion - GR admits solutions describing a dynamic, expanding or contracting universe, foundational to modern cosmology.

Each of these predictions has been confirmed observationally to high precision. Gravitational waves were first observed in September 2015 by the LIGO collaboration and announced publicly in February 2016, 100 years after Einstein's publication. Black hole shadows were imaged by the Event Horizon Telescope beginning in 2019.

General relativity is not a complete theory of nature. It is a classical (non-quantum) field theory and breaks down at singularities - points of infinite curvature predicted to exist inside black holes and at the Big Bang. Reconciling GR with quantum mechanics remains one of the central unsolved problems in physics. Candidate frameworks include string theory, loop quantum gravity, and causal dynamical triangulation, none of which has yet produced testable predictions that distinguish it from competitors at accessible energy scales. See Quantum Gravity and String Theory.

In everyday and engineering contexts, Newtonian gravity remains an excellent approximation. General relativistic corrections are, however, necessary for the Global Positioning System (GPS), whose satellite clocks must account for both gravitational time dilation (a GR effect) and velocity-based time dilation, the latter described by Special Relativity.

Einstein developed general relativity over roughly a decade, building on special relativity (1905) and working through the mathematics of differential geometry with collaborator Marcel Grossmann. The field equations were presented to the Prussian Academy of Sciences in November 1915. Early confirmations came from the correct prediction of Mercury's anomalous perihelion precession and from the observation of gravitational light-bending during the solar eclipse of 29 May 1919, organized by Arthur Eddington. For fuller treatment, see General Relativity - History.

There is strong consensus across physics and astronomy that general relativity correctly describes gravitational phenomena across a wide range of scales and field strengths, and that it has passed every empirical test to date. See General Relativity - Physics Consensus. Consensus does not extend to questions of quantum gravity, the interpretation of singularities, or the ultimate ontological status of spacetime.

While the empirical success of GR is not seriously disputed within mainstream physics, interpretive and foundational questions remain active:

• Spacetime realism vs. relationism - whether spacetime is a genuine physical entity or a mathematical bookkeeping structure. See Spacetime Realism Viewpoint.
• Singularities and cosmic censorship - whether singularities are physical features of the universe or breakdowns of the theory. See Singularities Viewpoint.
• Modifications to GR - alternatives such as MOND (Modified Newtonian Dynamics) and scalar-tensor theories attempt to explain anomalies (galactic rotation curves, cosmological acceleration) without dark matter or dark energy. See MOND Viewpoint and Dark Matter.
• Cosmological interpretation - the application of GR to the universe as a whole requires assumptions (homogeneity, isotropy, initial conditions) that carry their own interpretive weight. See Standard Cosmological Model Viewpoint.

• General Relativity - History
• General Relativity - Physics Consensus
• General Relativity - Debate
• Special Relativity
• Quantum Gravity
• Black Holes
• Gravitational Waves
• Dark Matter
• Dark Energy
• Cosmology
• Modified Gravity
• String Theory

1. Einstein, A. (1915). “Die Feldgleichungen der Gravitation.” Sitzungsberichte der Preussischen Akademie der Wissenschaften zu Berlin. pp. 844-847.
2. Misner, C. W., Thorne, K. S., & Wheeler, J. A. (1973). Gravitation. W. H. Freeman.
3. Will, C. M. (2014). “The Confrontation between General Relativity and Experiment.” Living Reviews in Relativity 17, 4.
4. Abbott, B. P. et al. (LIGO Scientific Collaboration and Virgo Collaboration). (2016). “Observation of Gravitational Waves from a Binary Black Hole Merger.” Physical Review Letters 116, 061102.
5. Event Horizon Telescope Collaboration. (2019). “First M87 Event Horizon Telescope Results.” The Astrophysical Journal Letters 875, L1.
6. Dyson, F. W., Eddington, A. S., & Davidson, C. (1920). “A Determination of the Deflection of Light by the Sun's Gravitational Field.” Philosophical Transactions of the Royal Society A 220, 291-333.