- 1640 — Ismaël Bullialdus suggests an inverse-square gravitational force law
- 1676 — Ole Rømer demonstrates that light has a finite speed
- 1684 — Isaac Newton writes down his inverse-square law of universal gravitation
- 1758 — Rudjer Josip Boscovich develops his theory of forces, where gravity can be repulsive on small distances. So according to him strange classical bodies, such as white holes, can exist, which won't allow other bodies to reach their surfaces
- 1784 — John Michell discusses classical bodies which have escape velocities greater than the speed of light
- 1795 — Pierre Laplace discusses classical bodies which have escape velocities greater than the speed of light
- 1798 — Henry Cavendish measures the gravitational constant
*G* - 1876 — William Kingdon Clifford suggests that the motion of matter may be due to changes in the geometry of space

- 1909 — Albert Einstein, together with Marcel Grossmann, starts to develop a theory which would bind metric tensor
*g*_{ik}, which defines a space geometry, with a source of gravity, that is with mass - 1910 — Hans Reissner and Gunnar Nordström defines Reissner–Nordström singularity, Hermann Weyl solves special case for a point-body source
- 1915 — Albert Einstein presents (David Hilbert presented this independently five days earlier in Göttingen) the complete Einstein field equations at the Prussian Academy meeting in Berlin on 25 November 1915
^{ [1] } - 1916 — Karl Schwarzschild solves the Einstein vacuum field equations for uncharged spherically-symmetric non-rotating systems
- 1917 — Paul Ehrenfest gives conditional principle a three-dimensional space
- 1918 — Hans Reissner and Gunnar Nordström solve the Einstein–Maxwell field equations for charged spherically-symmetric non-rotating systems
- 1918 — Friedrich Kottler gets Schwarzschild solution without Einstein vacuum field equations
- 1923 — George David Birkhoff proves that the Schwarzschild spacetime geometry is the unique spherically symmetric solution of the Einstein vacuum field equations
- 1931 — Subrahmanyan Chandrasekhar calculates, using special relativity, that a non-rotating body of electron-degenerate matter above a certain limiting mass (at 1.4 solar masses) has no stable solutions
- 1939 — Robert Oppenheimer and Hartland Snyder calculate the gravitational collapse of a pressure-free homogeneous fluid sphere into a black hole
- 1958 — David Finkelstein theorises that the Schwarzschild radius is a causality barrier: an event horizon of a black hole

- 1963 — Roy Kerr solves the Einstein vacuum field equations for uncharged symmetric rotating systems, deriving the Kerr metric for a rotating black hole
- 1963 — Maarten Schmidt discovers and analyzes the first quasar, 3C 273, as a highly red-shifted active galactic nucleus, a billion light years away
- 1964 — Roger Penrose proves that an imploding star will necessarily produce a singularity once it has formed an event horizon
- 1964 — Yakov Zel’dovich and independently Edwin Salpeter propose that accretion discs around supermassive black holes are responsible for the huge amounts of energy radiated by quasars
^{ [1] } - 1964 — Hong-Yee Chiu coins the word
*quasar*for a 'quasi-stellar radio source' in his article in Physics Today - 1964 — The first recorded use of the term "black hole", by journalist Ann Ewing
- 1965 — Ezra T. Newman, E. Couch, K. Chinnapared, A. Exton, A. Prakash, and Robert Torrence solve the Einstein–Maxwell field equations for charged rotating systems
- 1966 — Yakov Zel’dovich and Igor Novikov propose searching for black hole candidates among binary systems in which one star is optically bright and X-ray dark and the other optically dark but X-ray bright (the black hole candidate)
^{ [1] } - 1967 — Jocelyn Bell discovers and analyzes the first radio pulsar, direct evidence for a neutron star
^{ [2] } - 1967 — Werner Israel presents the proof of the no-hair theorem at King's College London
- 1967 — John Wheeler introduces the term "black hole" in his lecture to the American Association for the Advancement of Science
^{ [1] } - 1968 — Brandon Carter uses Hamilton–Jacobi theory to derive first-order equations of motion for a charged particle moving in the external fields of a Kerr–Newman black hole
- 1969 — Roger Penrose discusses the Penrose process for the extraction of the spin energy from a Kerr black hole
- 1969 — Roger Penrose proposes the cosmic censorship hypothesis

- 1972 — Identification of Cygnus X-1/HDE 226868 from dynamic observations as the first binary with a stellar black hole candidate
- 1972 — Stephen Hawking proves that the area of a classical black hole's event horizon cannot decrease
- 1972 — James Bardeen, Brandon Carter, and Stephen Hawking propose four laws of black hole mechanics in analogy with the laws of thermodynamics
- 1972 — Jacob Bekenstein suggests that black holes have an entropy proportional to their surface area due to information loss effects
- 1974 — Stephen Hawking applies quantum field theory to black hole spacetimes and shows that black holes will radiate particles with a black-body spectrum which can cause black hole evaporation
- 1975 — James Bardeen and Jacobus Petterson show that the swirl of spacetime around a spinning black hole can act as a gyroscope stabilizing the orientation of the accretion disc and jets
^{ [1] } - 1989 — Identification of microquasar V404 Cygni as a binary black hole candidate system
- 1994 — Charles Townes and colleagues observe ionized neon gas swirling around the center of our Galaxy at such high velocities that a possible black hole mass at the very center must be approximately equal to that of 3 million suns
^{ [3] }

- 2002 — Astronomers at the Max Planck Institute for Extraterrestrial Physics present evidence for the hypothesis that Sagittarius A* is a supermassive black hole at the center of the Milky Way galaxy
- 2002 — NASA's Chandra X-ray Observatory identifies double galactic black holes system in merging galaxies NGC 6240
- 2004 — Further observations by a team from UCLA present even stronger evidence supporting Sagittarius A* as a black hole
- 2006 — The Event Horizon Telescope begins capturing data
- 2012 — First visual evidence of black-holes: Suvi Gezari's team in Johns Hopkins University, using the Hawaiian telescope Pan-STARRS 1, publish images of a supermassive black hole 2.7 million light-years away swallowing a red giant
^{ [4] } - 2015 — LIGO Scientific Collaboration detects the distinctive gravitational waveforms from a binary black hole merging into a final black hole, yielding the basic parameters (e.g., distance, mass, and spin) of the three spinning black holes involved
- 2019 — Event Horizon Telescope collaboration releases the first direct photo of a black hole, the supermassive M87* at the core of the Messier 87 galaxy

A **black hole** is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly.

The weak and the strong **cosmic censorship hypotheses** are two mathematical conjectures about the structure of gravitational singularities arising in general relativity.

**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. 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. The relation is specified by the Einstein field equations, a system of second order partial differential equations.

In physics, **gravity** (from Latin * gravitas* 'weight') is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 10^{38} times weaker than the strong interaction, 10^{36} times weaker than the electromagnetic force and 10^{29} times weaker than the weak interaction. As a result, it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.

A **gravitational singularity**, **spacetime singularity** or simply **singularity** is a condition in which gravity is predicted to be so intense that spacetime itself would break down catastrophically. As such, a singularity is by definition no longer part of the regular spacetime and cannot be determined by "where" or "when". Gravitational singularities exist at a junction between general relativity and quantum mechanics; therefore, the properties of the singularity cannot be described without an established theory of quantum gravity. Trying to find a complete and precise definition of singularities in the theory of general relativity, the current best theory of gravity, remains a difficult problem. A singularity in general relativity can be defined by the scalar invariant curvature becoming infinite or, better, by a geodesic being incomplete.

The following is a **timeline of gravitational physics and general relativity**.

The **Schwarzschild radius** or the **gravitational radius** is a physical parameter in the Schwarzschild solution to Einstein's field equations that corresponds to the radius defining the event horizon of a Schwarzschild black hole. It is a characteristic radius associated with any quantity of mass. The Schwarzschild radius was named after the German astronomer Karl Schwarzschild, who calculated this exact solution for the theory of general relativity in 1916.

In general relativity, a **white hole** is a hypothetical region of spacetime and singularity that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black hole, from which energy-matter, light and information cannot escape. White holes appear in the theory of eternal black holes. In addition to a black hole region in the future, such a solution of the Einstein field equations has a white hole region in its past. This region does not exist for black holes that have formed through gravitational collapse, however, nor are there any observed physical processes through which a white hole could be formed.

In Einstein's theory of general relativity, the **Schwarzschild metric** is an exact solution to the Einstein field equations that describes the gravitational field outside a spherical mass, on the assumption that the electric charge of the mass, angular momentum of the mass, and universal cosmological constant are all zero. The solution is a useful approximation for describing slowly rotating astronomical objects such as many stars and planets, including Earth and the Sun. It was found by Karl Schwarzschild in 1916, and around the same time independently by Johannes Droste, who published his more complete and modern-looking discussion four months after Schwarzschild.

The **Penrose–Hawking singularity theorems** are a set of results in general relativity that attempt to answer the question of when gravitation produces singularities. The **Penrose singularity theorem** is a theorem in semi-Riemannian geometry and its general relativistic interpretation predicts a gravitational singularity in black hole formation. The **Hawking singularity theorem** is based on the Penrose theorem and it is interpreted as a gravitational singularity in the Big Bang situation. Penrose was awarded the Nobel Prize in Physics in 2020 "for the discovery that black hole formation is a robust prediction of the general theory of relativity", which he shared with Reinhard Genzel and Andrea Ghez.

The **Kerr metric** or **Kerr geometry** describes the geometry of empty spacetime around a rotating uncharged axially symmetric black hole with a quasispherical event horizon. The Kerr metric is an exact solution of the Einstein field equations of general relativity; these equations are highly non-linear, which makes exact solutions very difficult to find.

A **charged black hole** is a black hole that possesses electric charge. Since the electromagnetic repulsion in compressing an electrically charged mass is dramatically greater than the gravitational attraction, it is not expected that black holes with a significant electric charge will be formed in nature.

In general relativity, a spacetime is said to be **static** if it does not change over time and is also irrotational. It is a special case of a stationary spacetime, which is the geometry of a stationary spacetime that does not change in time but can rotate. Thus, the Kerr solution provides an example of a stationary spacetime that is **not** static; the non-rotating Schwarzschild solution is an example that is static.

An **asymptotically flat spacetime** is a Lorentzian manifold in which, roughly speaking, the curvature vanishes at large distances from some region, so that at large distances, the geometry becomes indistinguishable from that of Minkowski spacetime.

General relativity is a theory of gravitation that was developed by Albert Einstein between 1907 and 1915, with contributions by many others after 1915. According to general relativity, the observed gravitational attraction between masses results from the warping of space and time by those masses.

In physics, there is a speculative hypothesis that, if there were a black hole with the same mass, charge and angular momentum as an electron, it would share other properties of the electron. Most notably, Brandon Carter showed in 1968 that the magnetic moment of such an object would match that of an electron. This is interesting because calculations ignoring special relativity and treating the electron as a small rotating sphere of charge give a magnetic moment roughly half the experimental value.

The following outline is provided as an overview of and topical guide to black holes:

**Negative energy** is a concept used in physics to explain the nature of certain fields, including the gravitational field and various quantum field effects.

- 1 2 3 4 5 Thorne, Kip S. (1994).
*Black holes and time warps : Einstein's outrageous legacy*. New York. ISBN 0393035050. OCLC 28147932. - ↑ Ferrarese, Laura; Ford, Holland (February 2005). "Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research".
*Space Science Reviews*.**116**(3–4): 523–624. arXiv: astro-ph/0411247 . Bibcode:2005SSRv..116..523F. doi:10.1007/s11214-005-3947-6. S2CID 119091861.it is fair to say that the single most influential event contributing to the acceptance of black holes was the 1967 discovery of pulsars by graduate student Jocelyn Bell. The clear evidence of the existence of neutron stars – which had been viewed with much skepticism until then – combined with the presence of a critical mass above which stability cannot be achieved, made the existence of stellar-mass black holes inescapable.

- ↑ Genzel, R; Hollenbach, D; Townes, C H (1994-05-01). "The nucleus of our Galaxy".
*Reports on Progress in Physics*.**57**(5): 417–479. Bibcode:1994RPPh...57..417G. doi:10.1088/0034-4885/57/5/001. ISSN 0034-4885. S2CID 250900662. - ↑ Scientific American – Big Gulp: Flaring Galaxy Marks the Messy Demise of a Star in a Supermassive Black Hole

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