| 1687 | Newton publishes his Principia, in which are formulated his concepts of absolute space and time, and his laws of motion and laws of gravity. [Ch. 1] |
| 1783&1795 | Michell and Laplace, using Newton’s laws of motion, gravity, and light, formulate the concept of a Newtonian black hole. [Ch. 3] |
| 1864 | Maxwell formulates his unified laws of electromagnetism. [Ch. 1] |
| 1887 | Michelson and Morley show, experimentally, that the speed of light is independent of the velocity of the Earth through absolute space. [Ch. 1] |
| 1905 | Einstein shows that space and time are relative rather than absolute, and formulates the special relativistic laws of physics. [Ch. 1] |
| Einstein shows that electromagnetic waves behave under some circumstances like particles, thereby initiating the concept of wave/particle duality that underlies quantum mechanics. [Ch. 4] |
| 1907 | Einstein, taking his first steps toward general relativity, formulates the concept of a local inertial frame and the equivalence principle, and deduces the gravitational dilation of time. [Ch. 2] |
| 1908 | Hermann Minkowski unifies space and time into an absolute four-dimensional spacetime. [Ch. 2] |
| 1912 | Einstein realizes that spacetime is curved, and that tidal gravity is a manifestation of that curvature. [Ch. 2] |
| 1915 | Einstein and Hilbert independently formulate the Einstein field equation (which describes how mass curves spacetime), thereby completing the laws of general relativity. [Ch. 2] |
| 1916 | Karl Schwarzschild discovers the Schwarzschild solution of the Einstein field equation, which later will turn out to describe nonspinning, uncharged black holes. [Ch. 3] |
| Flamm discovers that, with an appropriate choice of topology, the Schwarzschild solution of the Einstein equation can describe a wormhole. [Ch. 14] |
| 1916&1918 | Reissner and Nordstrom discover their solution of the Einstein field equation, which later will describe nonspinning, charged black holes. [Ch. 7] |
| 1926 | Eddington poses the mystery of the white dwarfs and attacks the reality of black holes. [Ch. 4] |
| Schrödinger and Heisenberg, building on others’ work, complete the formulation of the quantum mechanical laws of physics. [Ch. 4] |
| Fowler uses the quantum mechanical laws to show how electron degeneracy resolves the mystery of the white dwarfs. [Ch. 4] |
| 1930 | Chandrasekhar discovers that there is a maximum mass for white dwarfs. [Ch. 4] |
| 1932 | Chadwick discovers the neutron. [Ch. 5] |
| 1933 | Jansky discovers cosmic radio waves. [Ch. 9] |
| 1934 | Landau creates his research group in the V.S.S.R. and begins to transfuse theoretical physics there from Western Europe. [Ch. 5, 13] |
| Baade and Zwicky identify supernovae, propose the concept of a neutron star, and suggest that supernovae are powered by the implosion of a stellar core to form a neutron star. [Ch. 5] |
| 1935 | Chandrasekhar makes more complete his demonstration of the maximum mass for white-dwarf stars, and Eddington attacks his work. [Ch. 4] |
| 1935–1939 | The Great Terror in the V.S.S.R. [Ch. 5, 6] |
| 1957 | Greenstein and Whipple demonstrate that Jansky’s cosmic radio waves cannot be explained by then-known astrophysical processes. [Ch. 9] |
| Landau, in a desperate attempt to avoid prison and death, proposes that stars are kept hot by energy released when matter flows onto neutron cores at their centers. [Ch. 5] |
| 1958 | Landau is imprisoned in Moscow on charges of spying for Germany. [Ch. 5] |
| Oppenheimer and Serber disprove Landau’s neutron core method for keeping stars hot; Oppenheimer and Volkoff show that there is a maximum mass for neutron stars. [Ch. 5] |
| Bethe and Critchfield show that the Sun and other stars are kept hot by burning nuclear fuel. [Ch.5] |
| 1939 | Landau, near death, is released from prison. [Ch. 5] |
| Einstein argues that black holes cannot exist in the real Universe. [Ch. 4] |
| Oppenheimer and Snyder, in a highly idealized calculation, show that an imploding star forms a black hole, and (paradoxically) that the implosion appears to freeze at the horizon as seen from the outside but not as seen from the star’s surface. [Ch. 6] |
| Reber discovers cosmic radio waves from distant galaxies, but does not know that is what he is seeing. [Ch. 9] |
| Bohr and Wheeler develop the theory of nuclear fission. [Ch. 6] |
| Khariton and Zel’dovich develop the theory of a chain reaction of nuclear fissions. [Ch. 6] |
| The German army invades Poland, setting off World War 11. |
| 1942 | The U.S. launches a crash program to develop the atomic bomb, led by Oppenheimer. [Ch. 6] |
| 1943 | The U.S.S.R. launches a low-level effort to design nuclear reactors and atomic bombs, with Zel’dovich as a lead theorist. [Ch. 6] |
| 1945 | The U.S. drops atomic bombs on Hiroshima and Nagasaki. World War 11 ends. A low-level U.S. effort to develop the superbomb is begun. [Ch. 6] |
| The U.S.S.R. launches a crash program to develop the atomic bomb, with Zel’dovich as a lead theorist. [Ch. 6] |
| 1946 | Friedman and his team launch the first astronomical instrument above the Earth’s atmosphere, on a captured German V-2 rocket. [Ch. 8] |
| Experimental physicists in England and Australia begin constructing radio telescopes and radio interferometers. [Ch. 9] |
| 1948 | Zel’dovich” Sakharov, Ginzburg, and others in the U.S.S.R. initiate design work for a superbomb (hydrogen bomb); Ginzburg invents the LiD fuel, Sakharov the layered-cake design. [Ch. 6] |
| 1949 | The U.S.S.R. explodes its first atomic bomb, setting off a debate in the U.S. about a crash program to develop the superbomb. The D.S.S.R. proceeds directly into a crash program for the superbomb, without debate. [Ch. 6] |
| 1950 | The V.S. launches a crash superbomb effort. [Ch. 6] |
| Kiepenheuer and Ginzburg realize that cosmic radio waves are produced by cosmic-ray electrons spiraling in interstellar magnetic fields. [Ch. 9] |
| Alexandrov and Pimenov initiate an ill-fated attempt to introduce topological tools into mathematical studies of curved spacetime. [Ch. 13] |
| 1951 | Teller and Vlam in the U.S. invent the idea for a “real” superbomb, one that can be arbitrarily powerful; Wheeler puts together a team to design a bomb based on the idea and simulate its explosion on computers. [Ch. 6] |
| Graham Smith provides Baade with a 1-arc-minute error box for the cosmic radio source Cyg A, and Baade discovers with an optical telescope that Cyg A is a distant galaxy—a “radio galaxy.” [Ch. 9] |
| 1952 | The U.S. explodes its first superbomb device, one too massive to be delivered by an airplane or rocket, but using the Teller–Vlam invention and based on the Wheeler team’s design work. [Ch. 6] |
| 1953 | Wheeler launches into research on general relativity. [Ch. 6] |
| Jennison and Das Gupta discover that the radio waves from galaxies are produced by two giant lobes on opposite sides of the galaxy. [Ch. 9] |
| Stalin dies. [Ch. 6] |
| The U.S.S.R. explodes its first hydrogen bomb, based on the Ginzburg and Sakharov ideas. It is claimed by U.S. scientists not to be a “real” superbomb because the design does not permit the bomb to be arbitrarily powerful. [Ch.6] |
| 1954 | Sakharov and Zel’dovich invent the Teller–Ulam idea for a “real” superbomb. [Ch. 6] |
| The U.S. explodes its first real superbomb, based on the Teller–Ulam/Sakharov–Zel’dovich idea. [Ch. 6] |
| Teller testifies against Oppenheimer, and Oppenheimer’s security clearance is revoked. [Ch. 6] |
| 1955 | The U.S.S.R. explodes its first real superbomb, based on the Teller–Ulam/Sakharov–Zel’dovich idea. [Ch. 6] |
| Wheeler formulates the concept of gravitational vacuum fluctuations, identifies the Planck–Wheeler length as the scale on which they become huge, and suggests that on this scale the concept of spacetime gets replaced by quantum foam. [Ch. 12, 13, 14] |
| 1957 | Wheeler, Harrison, and Wakano formulate the concept of cold, dead matter and make a catalog of all possible cold, dead stars. Their catalog firms up the conclusion that massive stars must implode when they die. [Ch. 5] |
| Wheeler’s group studies wormholes; Regge and Wheeler invent perturbation methods for analyzing small perturbations of wormholes; their formalism later will be used to study perturbations of black holes. [Ch. 7, 14] |
| Wheeler poses the issue of the final state of stellar implosion as a holy grail for research and, in a confrontation with Oppenheimer, opposes the idea that the final state will be hidden inside a black hole. [Ch. 6, 13J |
| 1958 | Finkelstein discovers a new reference frame for the Schwarzschild geometry, and it resolves the 1939 Oppenheimer–Snyder paradox of why an imploding star freezes at the critical circumference as seen from outside but implodes through the critical circumference as seen from inside. [Ch. 6] |
| 1958–1960 | Wheeler gradually embraces the concept of a black hole and becomes its leading proponent. [Ch. 6] |
| 1959 | Wheeler argues that spacetime singularities formed in the big crunch or inside a black hole are governed by the laws of quantum gravity, and may consist of quantum foam. [Ch. 13] |
| Burbidge shows that the giant lobes of radio galaxies contain magnetic and kinetic energy equivalent to that obtained by a perfect conversion of 10 million Suns into pure energy. [Ch. 9] |
| 1960 | Weber initiates construction of bar detectors for gravitational waves. [Ch. 10] |
| Kruskal shows that, if it is not threaded by any material, a spherical worm-hole will pinch off so quickly that it cannot be traversed. [Ch. 14] |
| Graves and Brill discover that the Reissner–Nordstrom solution of Einstein’s equation describes a spherical, electrically charged black hole and also a wormhole. [Ch. 7] Their work suggests (incorrectly) that it might be possible to travel from the interior of a black hole in our Universe through hyperspace and into some other universe. [Ch. 13] |
| 1961 | Khalatnikov and Lifshitz argue (incorrectly) that Einstein’s field equation does not permit the existence of singularities with randomly deformed curvature, and therefore singularities cannot form inside real black holes or in the Universe’s big crunch. [Ch. 13] |
| 1961–1962 | Zel’dovich begins research on astrophysics and general relativity, recruits Novikov, and begins to build his research team. [Ch. 6] |
| 1962 | Thorne begins research under Wheeler’s guidance and initiates research that will lead to the hoop conjecture. [Ch. 7] |
| Giacconi and his team discover cosmic X-rays, using a Geiger counter flown above the Earth’s atmosphere on an Aerobee rocket. [Ch. 8] |
| 1963 | Kerr discovers his solution of Einstein’s field equation. [Ch. 7] |
| Schmidt, Greenstein, and Sandage discover quasars. [Ch. 9] |
| 1964 | The golden age of theoretical black-hole research begins. [Ch. 7] |
| Penrose introduces topology as a tool in relativity research, and uses it to prove that singularities must reside inside all black holes. [Ch. 13] |
| Ginzburg and then Doroshkevich, Novikov, and Zel’dovich discover the first evidence that a black hole has no “hair.” [Ch. 7] |
| Colgate, May, and White in the U.S., and Podurets, Imshennik, and Nadezhin in the U.S.S.R., adapt bomb design computer codes to simulate realistic implosions of stellar cores; they confirm Zwicky’s 1934 speculation that implosions with low mass will form a neutron star and trigger a supernova, and confirm the 1939 Oppenheimer–Snyder conclusion that implosions with larger mass will create a black hole. [Ch. 6] |
| Zel’dovich, Guseinov, and Salpeter make the first proposals for how to search for black holes in the real Universe. [Ch. 8] |
| Salpeter and Zel’dovich speculate (correctly) that supermassive black holes power quasars and radio galaxies. [Ch. 9] |
| Herbert Friedman and his team discover Cygnus X-1, using a Geiger counter flown on a rocket. [Ch. 8] |
| 1965 | Boyer and Lindquist, Carter, and Penrose discover that Kerr’s solution of Einstein’s field equation describes a spinning black hole. [Ch. 7] |
| 1966 | Zel’dovich and Novikov propose searching for black holes in binaries where one object emits X-rays and the other light; this method will succeed in the 1970s (probably). [Ch. 8] |
| Geroch shows that the topology of space can change (for example, a worm-hole can form) non–quantum mechanically only if a time machine is created in the process, at least momentarily. [Ch. 14] |
| 1967 | Wheeler coins the name black hole. [Ch. 7] |
| Israel proves rigorously the first piece of the black-hole, no-hair conjecture: A nonspinning black hole must be precisely spherical. [Ch. 7] |
| 1968 | Penrose argues that it is impossible to travel from the interior of a black hole in our Universe through hyperspace and into some other universe; others, in the 1970s, will confirm that his argument is correct. [Ch. 13] |
| Carter discovers the nature of the swirl of space around a spinning black hole and its influence on infalling particles. [Ch. 7] |
| Misner and independently Belinsky, Khalatnikov, and Lifshitz discover the oscillatory “mixmaster” singularity as a solution of Einstein’s equation. [Ch. 13] |
| 1969 | Hawking and Penrose prove that our Universe must have had a singularity at the beginning of its big bang expansion. [Ch. 13] |
| Belinsky, Khalatnikov, and Lifshitz discover the oscillatory BKL singularity as a solution of Einstein’s equation; they show that it has random deformations of its spacetime curvature and argue that therefore it is the type of singularity that forms inside black holes and in the big crunch. [Ch. 13] |
| Penrose discovers that a spinning black hole stores enormous energy in the swirling motion of space around it, and that this rotational energy can be extracted. [Ch. 7] |
| Penrose proposes his cosmic censorship conjecture, that the laws of physics prevent naked singularities from forming. [Ch. 13] |
| Lynden-Bell proposes that gigantic black holes reside in the nuclei of galaxies and are surrounded by accretion disks. [Ch. 9] |
| Christodoulou notices a similarity between the evolution of a black hole when it slowly accretes matter and the laws of thermodynamics. [Ch. 12] |
| Weber announces tentative observational evidence for the existence of gravitational waves, triggering many other experimenters to start constructing bar detectors. By 1975 it will be clear he was not seeing waves. [Ch. 10] |
| Braginsky discovers evidence that there will be a quantum limit on the sensitivities of gravitational-wave detectors. [Ch. 10] |
| 1970 | Bardeen shows that the accretion of gas is likely to make typical black holes in our Universe spin very rapidly. [Ch. 9] |
| Price, building on work of Penrose, Novikov, and Chase, de la Cruz, and Israel, shows that black holes lose their hair by radiating it away, and he proves that anything which can be radiated will be radiated away completely. [Ch. 7] |
| Hawking formulates the concept of a black hole’s absolute horizon and proves that the surface areas of absolute horizons always increase. [Ch. 12] |
| Giacconi’s team constructs Uhuru, the first X-ray detector on a satellite; it is launched into orbit. [Ch. 8] |
| 1971 | Combined X-ray, radio-wave, and optical observations begin to bring strong evidence that Cygnus X-1 is a black hole orbiting a normal star. [Ch. 8] |
| Weiss at MIT and Forward at Hughes pioneer interferometric detectors for gravitational waves. [Ch. 10] |
| Rees proposes that a radio galaxy’s giant lobes are powered by jets that shoot out of the galaxy’s core. [Ch. 9] |
| Hanni and Ruffini formulate the concept of surface charge on a horizon, a foundation for the membrane paradigm. [Ch. 11] |
| Press discovers that black holes can pulsate. [Ch. 7] |
| Zel’dovich speculates that spinning black holes radiate, and Zel’dovich and Starobinsky use the laws of quantum fields in curved spacetime to justify Zel’dovich’s speculation. [Ch. 12] |
| Hawking points out that tiny “primordial” black holes might have been created in the big bang. [Ch. 12] |
| 1972 | Carter, building on work by Hawking and Israel, proves the no-hair conjecture for spinning, uncharged black holes (except for some technical details filled in later by Robinson). He shows that such a black hole is always described by Kerr’s solution of Einstein’s equation. [Ch. 7] |
| Thorne proposes the hoop conjecture as a criterion for when black holes form. [Ch. 7] |
| Bekenstein conjectures that a black hole’s surface area is its entropy in disguise, and conjectures that the hole’s entropy is the logarithm of the number of ways the hole could have been made. Hawking argues vigorously against this conjecture. [Ch. 12] |
| Bardeen, Carter, and Hawking formulate the laws of evolution of black holes in a form that is identical to the laws of thermodynamics, but maintain that the horizon’s surface area cannot be the hole’s entropy in disguise. [Ch. 12] |
| Teukolsky develops perturbation methods to describe the pulsations of spinning black holes. [Ch. 7] |
| 1973 | Press and Teukolsky prove that the pulsations of a spinning black hole are stable; they do not grow by feeding off the hole’s rotational energy. [Ch. 7] |
| 1974 | Hawking shows that all black holes, spinning or nonspinning, radiate precisely as though they had a temperature that is proportional to their surface gravity, and they thereby evaporate. He then recants his claim that the laws of black-hole mechanics are not the laws of thermodynamics in disguise and recants his critique of Bekenstein’s conjecture that a hole’s surface area is its entropy in disguise. [Ch. 12] |
| 1974–1978 | Blandford, Rees, and Lynden-Bell identify several methods by which supermassive black holes in the nuclei of galaxies and quasars can create jets. [Ch. 9] |
| 1975 | Bardeen and Petterson show that the swirl of space around a spinning black hole can act as a gyroscope to maintain the directions of jets. [Ch. 9] |
| Chandrasekhar embarks on a five-year quest to develop a complete mathematical description of perturbations of black holes. [Ch. 7] |
| Unruh and Davies infer that, as seen by accelerating observers just above a black hole’s horizon, the hole is surrounded by a hot atmosphere of particles, whose gradual escape accounts for the hole’s evaporation. [Ch. 12] |
| Page computes the spectrum of particles radiated by black holes. Hawking and Page, from observational data on cosmic gamma rays, infer that there can be no more than 300 tiny, primordial, evaporating black holes in each cubic light-year of space. [Ch. 12] |
| The golden age of theoretical black-hole research is declared finished by youthful researchers. [Ch. 7] |
| 1977 | Gibbons and Hawking verify Bekenstein’s conjecture that a black hole’s entropy is the logarithm of the number of ways it might have been made. [Ch. 12] |
| Radio astronomers use interferometers to discover the jets that feed power from a galaxy’s central black-hole engine to its giant radio-emitting lobes. [Ch. 9] |
| Blandford and Znajek show that magnetic fields, threading the horizon of a spinning black hole, can extract the hole’s spin energy, and that the extracted energy can power quasars and radio galaxies. [Ch. 9] |
| Znajek and Damour formulate the membrane description of a black-hole horizon. [Ch. 11] |
| Braginsky and colleagues, and Caves, Thorne, and colleagues, devise quantum nondemolition sensors for circumventing the quantum limit on bar detectors of gravitational waves. [Ch. 10] |
| 1978 | Giacconi’s group completes construction of the first high-resolution X-ray telescope, called “Einstein,” and it is launched into orbit. [Ch. 8]1 |
| 1979 | Townes and others discover evidence for a 3-million-solar-mass black hole at the center of our galaxy. [Ch. 9] |
| Drever initiates an interferometric gravitational-wave detection project at Caltech.[Ch. 10] |
| 1982 | Bunting and Mazur prove the no-hair conjecture for spinning, electrically charged black holes. [Ch. 7] |
| 1983–1988 | Phinney and others develop comprehensive black-hole-based models to explain the full details of quasars and radio galaxies. [Ch. 9] |
| 1984 | The National Science Foundation forges a shotgun marriage between the Caltech and MIT gravitational-wave detection efforts, giving rise to the LIGO Project. [Ch. 10] |
| Redmount (building on earlier work by Eardley) shows that radiation falling into an empty, spherical wormhole gets accelerated to high energy and greatly speeds up the wormhole’s pinch-off. [Ch. 14] |
| 1985–1993 | Thorne, Morris, Yurtsever, Friedman, Novikov, and others probe the laws of physics by asking whether they permit traversable wormholes and time machines. [Ch. 14] |
| 1987 | Vogt becomes director of the LIGO Project, and it then begins to move forward vigorously. [Ch. 10] |
| 1990 | Kim and Thorne show that, whenever one tries to create a time machine, by any method whatsoever, an intense beam of vacuum fluctuations circulates through the machine at the moment it is first created. [Ch. 14] |
| 1991 | Hawking proposes the chronology protection conjecture (that the laws of physics forbid time machines) and argues that it will be enforced by the circulating beam of vacuum fluctuations destroying any time machine at its moment of formation. [Ch. 14] |
| Israel, Poisson, and Ori, building on work by Doroshkevich and Novikov, show that the singularity inside a black hole ages; Ori shows that when the hole is old and quiescent, infalling objects do not get strongly deformed by the singularity’s tidal gravity until the moment they hit its quantum gravity core. [Ch. 13] |
| Shapiro and Teukolsky discover evidence, in supercomputer simulations, that the cosmic censorship conjecture might be wrong: Naked singularities might be able to form when highly nonspherical stars implode. [Ch. 13] |
| 1993 | Hulse and Taylor are awarded the Nobel Prize for demonstrating, by measurements of a binary pulsar, that gravitational waves exist. [Ch. 10] |
