Quantum gravity

Part of a series of articles about
General relativity
[math]\displaystyle{ G_{\mu \nu} + \Lambda g_{\mu \nu}= {8\pi G\over c^4} T_{\mu \nu} }[/math]
Introduction History Mathematical formulation Tests
Fundamental concepts Principle of relativity Theory of relativity Frame of reference Inertial frame of reference Rest frame Center-of-momentum frame Equivalence principle Mass–energy equivalence Special relativity Doubly special relativity de Sitter invariant special relativity World line Riemannian geometry
Phenomena Gravitoelectromagnetism Kepler problem Gravity Gravitational field Gravity well Gravitational lensing Gravitational waves Gravitational redshift Redshift Blueshift Time dilation Gravitational time dilation Shapiro time delay Gravitational potential Gravitational compression Gravitational collapse Frame-dragging Geodetic effect Gravitational singularity Event horizon Naked singularity Black hole White hole Spacetime Space Time Spacetime diagrams Minkowski spacetime Closed timelike curve (CTC) Wormhole Ellis wormhole
Equations Formalisms Equations Linearized gravity Einstein field equations Friedmann Geodesics Mathisson–Papapetrou–Dixon Hamilton–Jacobi–Einstein Curvature invariant (general relativity) Lorentzian manifold Formalisms ADM BSSN Post-Newtonian Advanced theory Kaluza–Klein theory Quantum gravity Supergravity
Solutions Schwarzschild (interior) Reissner–Nordström Gödel Kerr Kerr–Newman Kasner Lemaître–Tolman Taub-NUT Milne Robertson–Walker pp-wave van Stockum dust Weyl−Lewis−Papapetrou Vacuum solution (general relativity) Vacuum solution
Scientists Einstein Lorentz Hilbert Poincaré Schwarzschild de Sitter Reissner Nordström Weyl Eddington Friedman Milne Zwicky Lemaître Gödel Wheeler Robertson Bardeen Walker Kerr Chandrasekhar Ehlers Penrose Hawking Raychaudhuri Taylor Hulse van Stockum Taub Newman Yau Thorne others

Quantum gravity is an area of research in physics. Right now, physics can describe gravity of real-life-sized objects using general relativity. Physicists can also describe the universe on a microscopic scale with quantum mechanics. The goal of quantum gravity is to develop a theory that contains both general relativity and quantum mechanics. However, combining the theories of the big and the small is very difficult in practice.

Physicists are working on several ways to write down a theory of quantum gravity. One approach is to search for a unified field theory. Physicists also try to develop theories at an even more fundamental level, like string theory, loop quantum gravity, or other methods, to find out why our current theories of gravity and quantum mechanics cannot be combined.