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Monday, July 14, 2025

Science fiction magazine

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Science_fiction_magazine
 
vampire, face of little green man, feather pen (quill) and fire-breathing dragon – to the right of that are scripted words "Speculative (over) Fiction"
Speculative fiction

A front cover of Imagination, a science fiction magazine in 1956

A science fiction magazine is a publication that offers primarily science fiction, either in a hard-copy periodical format or on the Internet. Science fiction magazines traditionally featured speculative fiction in short story, novelette, novella or (usually serialized) novel form, a format that continues into the present day. Many also contain editorials, book reviews or articles, and some also include stories in the fantasy and horror genres.

History of science fiction magazines

See also: History of US science fiction and fantasy magazines to 1950

Malcolm Edwards and Peter Nicholls write that early magazines were not known as science fiction: "if there were any need to differentiate them, the terms scientific romance or 'different stories' might be used, but until the appearance of a magazine specifically devoted to sf there was no need of a label to describe the category. The first specialized English-language pulps with a leaning towards the fantastic were Thrill Book (1919) and Weird Tales (1923), but the editorial policy of both was aimed much more towards weird-occult fiction than towards sf."

Major American science fiction magazines include Amazing Stories, Astounding Science Fiction, Galaxy Science Fiction, The Magazine of Fantasy & Science Fiction and Isaac Asimov's Science Fiction Magazine. The most influential British science fiction magazine was New Worlds; newer British SF magazines include Interzone and Polluto. Many science fiction magazines have been published in languages other than English, but none has gained worldwide recognition or influence in the world of anglophone science fiction.

There is a growing trend toward important work being published first on the Internet, both for reasons of economics and access. A web-only publication can cost as little as one-tenth of the cost of publishing a print magazine, and as a result, some believe the e-zines are more innovative and take greater risks with material. Moreover, the magazine is internationally accessible, and distribution is not an issue—though obscurity may be. Magazines like Strange Horizons, Ideomancer, InterGalactic Medicine Show, Jim Baen's Universe, and the Australian magazine Andromeda Spaceways Inflight Magazine are examples of successful Internet magazines. (Andromeda provides copies electronically or on paper.)

Web-based magazines tend to favor shorter stories and articles that are easily read on a screen, and many of them pay little or nothing to the authors, thus limiting their universe of contributors. However, multiple web-based magazines are listed as "paying markets" by the SFWA, which means that they pay the "professional" rate of 8c/word or more. These magazines include popular titles such as Strange Horizons, InterGalactic Medicine Show, and Clarkesworld Magazine. The SFWA publishes a list of qualifying magazine and short fiction venues that contains all current web-based qualifying markets.

The World Science Fiction Convention (Worldcon) awarded a Hugo Award each year to the best science fiction magazine, until that award was changed to one for Best Editor in the early 1970s; the Best Semi-Professional Magazine award can go to either a news-oriented magazine or a small press fiction magazine.

Magazines were the only way to publish science fiction until about 1950, when large mainstream publishers began issuing science fiction books. Today, there are relatively few paper-based science fiction magazines, and most printed science fiction appears first in book form. Science fiction magazines began in the United States, but there were several major British magazines and science fiction magazines that have been published around the world, for example in France and Argentina.

The first science fiction magazines

March 1941 cover of the Science Fiction magazine, volume 2, issue 4

The first science fiction magazine, Amazing Stories, was published in a format known as bedsheet, roughly the size of Life but with a square spine. Later, most magazines changed to the pulp magazine format, roughly the size of comic books or National Geographic but again with a square spine. Now, most magazines are published in digest format, roughly the size of Reader's Digest, although a few are in the standard roughly 8.5" x 11" size, and often have stapled spines, rather than glued square spines. Science fiction magazines in this format often feature non-fiction media coverage in addition to the fiction. Knowledge of these formats is an asset when locating magazines in libraries and collections where magazines are usually shelved according to size.

The premiere issue of Amazing Stories (April 1926), edited and published by Hugo Gernsback, displayed a cover by Frank R. Paul illustrating Off on a Comet by Jules Verne. After many minor changes in title and major changes in format, policy and publisher, Amazing Stories ended January 2005 after 607 issues.

Except for the last issue of Stirring Science Stories, the last true bedsheet size sf (and fantasy) magazine was Fantastic Adventures, in 1939, but it quickly changed to the pulp size, and it was later absorbed by its digest-sized stablemate Fantastic in 1953. Before that consolidation, it ran 128 issues.

Much fiction published in these bedsheet magazines, except for classic reprints by writers such as H. G. Wells, Jules Verne and Edgar Allan Poe, is only of antiquarian interest. Some of it was written by teenage science fiction fans, who were paid little or nothing for their efforts. Jack Williamson for example, was 19 when he sold his first story to Amazing Stories. His writing improved greatly over time, and until his death in 2006, he was still a publishing writer at age 98.

Some of the stories in the early issues were by scientists or doctors who knew little or nothing about writing fiction, but who tried their best, for example, David H. Keller. Probably the two best original sf stories ever published in a bedsheet science fiction magazine were "A Martian Odyssey" by Stanley G. Weinbaum and "The Gostak and the Doshes" by Miles Breuer, who influenced Jack Williamson. "The Gostak and the Doshes" is one of the few stories from that era still widely read today. Other stories of interest from the bedsheet magazines include the first Buck Rogers story, Armageddon 2419 A.D, by Philip Francis Nowlan, and The Skylark of Space by coauthors E. E. Smith and Mrs. Lee Hawkins Garby, both in Amazing Stories in 1928.

There have been a few unsuccessful attempts to revive the bedsheet size using better quality paper, notably Science-Fiction Plus edited by Hugo Gernsback (1952–53, eight issues). Astounding on two occasions briefly attempted to revive the bedsheet size, with 16 bedsheet issues in 1942–1943 and 25 bedsheet issues (as Analog, including the first publication of Frank Herbert's Dune) in 1963–1965. The fantasy magazine Unknown, also edited by John W. Campbell, changed its name to Unknown Worlds and published ten bedsheet-size issues before returning to pulp size for its final four issues. Amazing Stories published 36 bedsheet size issues in 1991–1999, and its last three issues were bedsheet size, 2004–2005.

The pulp era

Main article: Science fiction and fantasy pulp magazines
See also: Pulp era of science fiction

Astounding Stories began in January 1930. After several changes in name and format (Astounding Science Fiction, Analog Science Fact & Fiction, Analog) it is still published today (though it ceased to be pulp format in 1943). Its most important editor, John W. Campbell, Jr., is credited with turning science fiction away from adventure stories on alien planets and toward well-written, scientifically literate stories with better characterization than in previous pulp science fiction. Isaac Asimov's Foundation Trilogy and Robert A. Heinlein's Future History in the 1940s, Hal Clement's Mission of Gravity in the 1950s, and Frank Herbert's Dune in the 1960s, and many other science fiction classics all first appeared under Campbell's editorship.

By 1955, the pulp era was over, and some pulp magazines changed to digest size. Printed adventure stories with colorful heroes were relegated to the comic books. This same period saw the end of radio adventure drama (in the United States). Later attempts to revive both pulp fiction and radio adventure have met with very limited success, but both enjoy a nostalgic following who collect the old magazines and radio programs. Many characters, most notably The Shadow, were popular both in pulp magazines and on radio.

Most pulp science fiction consisted of adventure stories transplanted, without much thought, to alien planets. Pulp science fiction is known for clichés such as stereotypical female characters, unrealistic gadgetry, and fantastic monsters of various kinds. However, many classic stories were first published in pulp magazines. For example, in the year 1939, all of the following renowned authors sold their first professional science fiction story to magazines specializing in pulp science fiction: Isaac Asimov, Robert A. Heinlein, Arthur C. Clarke, Alfred Bester, Fritz Leiber, A. E. van Vogt and Theodore Sturgeon. These were among the most important science fiction writers of the pulp era, and all are still read today.

Digest-sized magazines

After the pulp era, digest size magazines dominated the newsstand. The first sf magazine to change to digest size was Astounding, in 1943. Other major digests, which published more literary science fiction, were The Magazine of Fantasy & Science Fiction, Galaxy Science Fiction and If. Under the editorship of Cele Goldsmith, Amazing and Fantastic changed in notable part from pulp style adventure stories to literary science fiction and fantasy. Goldsmith published the first professionally published stories by Roger Zelazny (not counting student fiction in Literary Cavalcade), Keith Laumer, Thomas M. Disch, Sonya Dorman and Ursula K. Le Guin.

There was also no shortage of digests that continued the pulp tradition of hastily written adventure stories set on other planets. Other Worlds and Imaginative Tales had no literary pretensions. The major pulp writers, such as Heinlein, Asimov and Clarke, continued to write for the digests, and a new generation of writers, such as Algis Budrys and Walter M. Miller, Jr., sold their most famous stories to the digests. A Canticle for Leibowitz, written by Walter M. Miller, Jr., was first published in The Magazine of Fantasy & Science Fiction.

Most digest magazines began in the 1950s, in the years between the film Destination Moon, the first major science fiction film in a decade, and the launching of Sputnik, which sparked a new interest in space travel as a real possibility. Most survived only a few issues. By 1960, in the United States, there were only six sf digests on newsstands, in 1970 there were seven, in 1980 there were five, in 1990 only four and in 2000 only three.

Around the world

British science fiction magazines

The first British science fiction magazine was Tales of Wonder, pulp size, 1937–1942, 16 issues, (unless Scoops is taken into account, a tabloid boys' paper that published 20 weekly issues in 1934). It was followed by two magazines, both named Fantasy, one pulp size publishing three issues in 1938–1939, the other digest size, publishing three issues in 1946–1947. The British science fiction magazine, New Worlds, published three pulp size issues in 1946–1947, before changing to digest size. With these exceptions, the pulp phenomenon, like the comic book, was largely a US format. By 2007, the only surviving major British science fiction magazine is Interzone, published in "magazine" format, although small press titles such as PostScripts and Polluto are available.

Transition from print to online science fiction magazines

During recent decades, the circulation of all digest science fiction magazines has steadily decreased. New formats were attempted, most notably the slick-paper stapled magazine format, the paperback format and the webzine. There are also various semi-professional magazines that persist on sales of a few thousand copies but often publish important fiction.

As the circulation of the traditional US science fiction magazines has declined, new magazines have sprung up online from international small-press publishers. An editor on the staff of Science Fiction World, China's longest-running science fiction magazine, claimed in 2009 that, with "a circulation of 300,000 copies per issue", it was "the World's most-read SF periodical", although subsequent news suggests that circulation dropped precipitously after the firing of its chief editor in 2010 and the departure of other editors. The Science Fiction and Fantasy Writers of America lists science fiction periodicals that pay enough to be considered professional markets.

List of current magazines

For a complete list, including defunct magazines, see List of science fiction magazines.

American magazines

British magazines

Other magazines

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History of string theory

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/History_of_string_theory
 
The history of string theory spans several decades of intense research including two superstring revolutions. Through the combined efforts of many researchers, string theory has developed into a broad and varied subject with connections to quantum gravity, particle and condensed matter physics, cosmology, and pure mathematics.

1943–1959: S-matrix theory

String theory represents an outgrowth of S-matrix theory, a research program begun by Werner Heisenberg in 1943 following John Archibald Wheeler's 1937 introduction of the S-matrix. Many prominent theorists picked up and advocated S-matrix theory, starting in the late 1950s and throughout the 1960s. The field became marginalized and discarded in the mid-1970s and disappeared in the 1980s. Physicists neglected it because some of its mathematical methods were alien, and because quantum chromodynamics supplanted it as an experimentally better-qualified approach to the strong interactions.

The theory presented a radical rethinking of the foundations of physical laws. By the 1940s it had become clear that the proton and the neutron were not pointlike particles like the electron. Their magnetic moment differed greatly from that of a pointlike spin-½ charged particle, too much to attribute the difference to a small perturbation. Their interactions were so strong that they scattered like a small sphere, not like a point. Heisenberg proposed that the strongly interacting particles were in fact extended objects, and because there are difficulties of principle with extended relativistic particles, he proposed that the notion of a space-time point broke down at nuclear scales.

Without space and time, it becomes difficult to formulate a physical theory. Heisenberg proposed a solution to this problem: focusing on the observable quantities—those things measurable by experiments. An experiment only sees a microscopic quantity if it can be transferred by a series of events to the classical devices that surround the experimental chamber. The objects that fly to infinity are stable particles, in quantum superpositions of different momentum states.

Heisenberg proposed that even when space and time are unreliable, the notion of momentum state, which is defined far away from the experimental chamber, still works. The physical quantity he proposed as fundamental is the quantum mechanical amplitude for a group of incoming particles to turn into a group of outgoing particles, and he did not admit that there were any steps in between.

The S-matrix is the quantity that describes how a collection of incoming particles turn into outgoing ones. Heisenberg proposed to study the S-matrix directly, without any assumptions about space-time structure. But when transitions from the far-past to the far-future occur in one step with no intermediate steps, it becomes difficult to calculate anything. In quantum field theory, the intermediate steps are the fluctuations of fields or equivalently the fluctuations of virtual particles. In this proposed S-matrix theory, there are no local quantities at all.

Heisenberg proposed to use unitarity to determine the S-matrix. In all conceivable situations, the sum of the squares of the amplitudes must equal 1. This property can determine the amplitude in a quantum field theory order by order in a perturbation series once the basic interactions are given, and in many quantum field theories the amplitudes grow too fast at high energies to make a unitary S-matrix. But without extra assumptions on the high-energy behavior, unitarity is not enough to determine the scattering, and the proposal was ignored for many years.

Heisenberg's proposal was revived in 1956 when Murray Gell-Mann recognized that dispersion relations—like those discovered by Hendrik Kramers and Ralph Kronig in the 1920s (see Kramers–Kronig relations)—allow the formulation of a notion of causality, a notion that events in the future would not influence events in the past, even when the microscopic notion of past and future are not clearly defined. He also recognized that these relations might be useful in computing observables for the case of strong interaction physics. The dispersion relations were analytic properties of the S-matrix, and they imposed more stringent conditions than those that follow from unitarity alone. This development in S-matrix theory stemmed from Murray Gell-Mann and Marvin Leonard Goldberger's (1954) discovery of crossing symmetry, another condition that the S-matrix had to fulfil.

Prominent advocates of the new "dispersion relations" approach included Stanley Mandelstam and Geoffrey Chew, both at UC Berkeley at the time. Mandelstam discovered the double dispersion relations, a new and powerful analytic form, in 1958, and believed that it would provide the key to progress in the intractable strong interactions.

1959–1968: Regge theory and bootstrap models

Main article: Regge theory

By the late 1950s, many strongly interacting particles of ever higher spins had been discovered, and it became clear that they were not all fundamental. While Japanese physicist Shoichi Sakata proposed that the particles could be understood as bound states of just three of them (the proton, the neutron and the Lambda; see Sakata model), Geoffrey Chew believed that none of these particles are fundamental (for details, see Bootstrap model). Sakata's approach was reworked in the 1960s into the quark model by Murray Gell-Mann and George Zweig by making the charges of the hypothetical constituents fractional and rejecting the idea that they were observed particles. At the time, Chew's approach was considered more mainstream because it did not introduce fractional charge values and because it focused on experimentally measurable S-matrix elements, not on hypothetical pointlike constituents.

Chew-Frautschi plot showing the angular momentum J as a function of the square mass of some particles. An example of Regge trajectories.

In 1959, Tullio Regge, a young theorist in Italy, discovered that bound states in quantum mechanics can be organized into families known as Regge trajectories, each family having distinctive angular momenta. This idea was generalized to relativistic quantum mechanics by Stanley Mandelstam, Vladimir Gribov and Marcel Froissart, using a mathematical method (the Sommerfeld–Watson representation) discovered decades earlier by Arnold Sommerfeld and Kenneth M. Watson: the result was dubbed the Froissart–Gribov formula.

In 1961, Geoffrey Chew and Steven Frautschi recognized that mesons had straight line Regge trajectories (in their scheme, spin is plotted against mass squared on a so-called Chew–Frautschi plot), which implied that the scattering of these particles would have very strange behavior—it should fall off exponentially quickly at large angles. With this realization, theorists hoped to construct a theory of composite particles on Regge trajectories, whose scattering amplitudes had the asymptotic form demanded by Regge theory.

In 1967, a notable step forward in the bootstrap approach was the principle of DHS duality introduced by Richard Dolen, David Horn, and Christoph Schmid in 1967, at Caltech (the original term for it was "average duality" or "finite energy sum rule (FESR) duality"). The three researchers noticed that Regge pole exchange (at high energy) and resonance (at low energy) descriptions offer multiple representations/approximations of one and the same physically observable process.

1968–1974: Dual resonance model

The first model in which hadronic particles essentially follow the Regge trajectories was the dual resonance model that was constructed by Gabriele Veneziano in 1968, who noted that the Euler beta function could be used to describe 4-particle scattering amplitude data for such particles. The Veneziano scattering amplitude (or Veneziano model) was quickly generalized to an N-particle amplitude by Ziro Koba and Holger Bech Nielsen (their approach was dubbed the Koba–Nielsen formalism), and to what are now recognized as closed strings by Miguel Virasoro and Joel A. Shapiro (their approach was dubbed the Shapiro–Virasoro model).

In 1969, the Chan–Paton rules (proposed by Jack E. Paton and Hong-Mo Chan) enabled isospin factors to be added to the Veneziano model.

In 1969–70, Yoichiro Nambu, Holger Bech Nielsen, and Leonard Susskind presented a physical interpretation of the Veneziano amplitude by representing nuclear forces as vibrating, one-dimensional strings. However, this string-based description of the strong force made many predictions that directly contradicted experimental findings.

In 1971, Pierre Ramond and, independently, John H. Schwarz and André Neveu attempted to implement fermions into the dual model. This led to the concept of "spinning strings", and pointed the way to a method for removing the problematic tachyon (see RNS formalism).

Dual resonance models for strong interactions were a relatively popular subject of study between 1968 and 1973. The scientific community lost interest in string theory as a theory of strong interactions in 1973 when quantum chromodynamics became the main focus of theoretical research (mainly due to the theoretical appeal of its asymptotic freedom).

1974–1984: Bosonic string theory and superstring theory

In 1974, John H. Schwarz and Joël Scherk, and independently Tamiaki Yoneya, studied the boson-like patterns of string vibration and found that their properties exactly matched those of the graviton, the gravitational force's hypothetical messenger particle. Schwarz and Scherk argued that string theory had failed to catch on because physicists had underestimated its scope. This led to the development of bosonic string theory.

String theory is formulated in terms of the Polyakov action, which describes how strings move through space and time. Like springs, the strings tend to contract to minimize their potential energy, but conservation of energy prevents them from disappearing, and instead they oscillate. By applying the ideas of quantum mechanics to strings it is possible to deduce the different vibrational modes of strings, and that each vibrational state appears to be a different particle. The mass of each particle, and the fashion with which it can interact, are determined by the way the string vibrates—in essence, by the "note" the string "sounds." The scale of notes, each corresponding to a different kind of particle, is termed the "spectrum" of the theory.

Early models included both open strings, which have two distinct endpoints, and closed strings, where the endpoints are joined to make a complete loop. The two types of string behave in slightly different ways, yielding two spectra. Not all modern string theories use both types; some incorporate only the closed variety.

The earliest string model has several problems: it has a critical dimension D = 26, a feature that was originally discovered by Claud Lovelace in 1971; the theory has a fundamental instability, the presence of tachyons (see tachyon condensation); additionally, the spectrum of particles contains only bosons, particles like the photon that obey particular rules of behavior. While bosons are a critical ingredient of the Universe, they are not its only constituents. Investigating how a string theory may include fermions in its spectrum led to the invention of supersymmetry (in the West) in 1971, a mathematical transformation between bosons and fermions. String theories that include fermionic vibrations are now known as superstring theories.

In 1977, the GSO projection (named after Ferdinando Gliozzi, Joël Scherk, and David I. Olive) led to a family of tachyon-free unitary free string theories, the first consistent superstring theories (see below).

1984–1994: First superstring revolution

The first superstring revolution is a period of important discoveries that began in 1984. It was realized that string theory was capable of describing all elementary particles as well as the interactions between them. Hundreds of physicists started to work on string theory as the most promising idea to unify physical theories. The revolution was started by a discovery of anomaly cancellation in type I string theory via the Green–Schwarz mechanism (named after Michael Green and John H. Schwarz) in 1984. The ground-breaking discovery of the heterotic string was made by David Gross, Jeffrey Harvey, Emil Martinec, and Ryan Rohm in 1985. It was also realized by Philip Candelas, Gary Horowitz, Andrew Strominger, and Edward Witten in 1985 that to obtain supersymmetry, the six small extra dimensions (the D = 10 critical dimension of superstring theory had been originally discovered by John H. Schwarz in 1972) need to be compactified on a Calabi–Yau manifold. (In string theory, compactification is a generalization of Kaluza–Klein theory, which was first proposed in the 1920s.)

By 1985, five separate superstring theories had been described: type I, type II (IIA and IIB), and heterotic (SO(32) and E8×E8).

Discover magazine in the November 1986 issue (vol. 7, #11) featured a cover story written by Gary Taubes, "Everything's Now Tied to Strings", which explained string theory for a popular audience.

In 1987, Eric Bergshoeff [de], Ergin Sezgin [de] and Paul Townsend showed that there are no superstrings in eleven dimensions (the largest number of dimensions consistent with a single graviton in supergravity theories), but supermembranes.

1994–2003: Second superstring revolution

In the early 1990s, Edward Witten and others found strong evidence that the different superstring theories were different limits of an 11-dimensional theory that became known as M-theory (for details, see Introduction to M-theory). These discoveries sparked the second superstring revolution that took place approximately between 1994 and 1995.

The different versions of superstring theory were unified, as long hoped, by new equivalences. These are known as S-duality, T-duality, U-duality, mirror symmetry, and conifold transitions. The different theories of strings were also related to M-theory.

In 1995, Joseph Polchinski discovered that the theory requires the inclusion of higher-dimensional objects, called D-branes: these are the sources of electric and magnetic Ramond–Ramond fields that are required by string duality. D-branes added additional rich mathematical structure to the theory, and opened possibilities for constructing realistic cosmological models in the theory (for details, see Brane cosmology).

In 1997–98, Juan Maldacena conjectured a relationship between type IIB string theory and N = 4 supersymmetric Yang–Mills theory, a gauge theory. This conjecture, called the AdS/CFT correspondence, has generated a great deal of interest in high energy physics. It is a realization of the holographic principle, which has far-reaching implications: the AdS/CFT correspondence has helped elucidate the mysteries of black holes suggested by Stephen Hawking's work and is believed to provide a resolution of the black hole information paradox.

2003–present

In 2003, Michael R. Douglas's discovery of the string theory landscape, which suggests that string theory has a large number of inequivalent false vacua, led to much discussion of what string theory might eventually be expected to predict, and how cosmology can be incorporated into the theory.

A possible mechanism of string theory vacuum stabilization (the KKLT mechanism) was proposed in 2003 by Shamit Kachru, Renata Kallosh, Andrei Linde, and Sandip Trivedi. Much of the present-day research is focused on characterizing the "swampland" of theories incompatible with quantum gravity. The Ryu–Takayanagi conjecture introduced many concepts from quantum information into string theory.

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Sunday, July 13, 2025

Timeline of the universe

From Wikipedia, the free encyclopedia
Diagram of Evolution of the universe from the Big Bang (left) to the present

The timeline of the universe begins with the Big Bang, 13.799 ± 0.021 billion years ago,  and follows the formation and subsequent evolution of the Universe up to the present day. Each era or age of the universe begins with an "epoch", a time of significant change. Times on this list are relative to the moment of the Big Bang.

First 20 minutes

Planck epoch

Grand unification epoch

Inflation

  • c. 10−35 seconds: inflation, expands the universe by a factor of the order of 1026 over a time of the order of 10−33 to 10−32 seconds. The universe is supercooled from about 1027 down to 1022 kelvin.
  • c. 10−32 seconds: Cosmic inflation ends.  The familiar elementary particles now form as a soup of hot ionized gas called quark–gluon plasma;

Quark epoch

Quark-hadron transition

  • c. 10−6 seconds: As the universe cools to about 1010 kelvin, a quark-hadron transition takes place in which quarks become confined in more complex particles—hadrons.

Lepton epoch

Photon epoch

  • c. 10 seconds: Photon epoch begins: Most leptons and antileptons annihilate each other. As electrons and positrons annihilate, a small number of unmatched electrons are left over – disappearance of the positrons.
  • c. 10 seconds: Universe dominated by photons of radiation – ordinary matter particles are coupled to light and radiation.
  • c. 3 minutes: Primordial nucleosynthesis: nuclear fusion begins as lithium and heavy hydrogen (deuterium) and helium nuclei form from protons and neutrons.
  • c. 20 minutes: Primordial nucleosynthesis ceases

Matter era

Matter and radiation equivalence

  • c. 47,000 years (z = 3600): Matter and radiation equivalence
  • c. 70,000 years: As the temperature falls, gravity overcomes pressure allowing first aggregates of matter to form.

Cosmic Dark Age

All-sky map of the CMB, created from nine years of WMAP data
  • c. 370,000 years (z = 1,100): The "Dark Ages" is the period between decoupling, when the universe first becomes transparent, until the formation of the first stars. Recombination: electrons combine with nuclei to form atoms, mostly hydrogen and helium. Ordinary matter particles decouple from radiation. The photons present during the decoupling are the same photons seen in the cosmic microwave background (CMB) radiation.
  • c. 10–17 million years: The "Dark Ages" span a period during which the temperature of cosmic microwave background radiation cooled from some 4,000 K (3,730 °C; 6,740 °F) down to about 60 K (−213.2 °C; −351.7 °F).

Reionization

  • c. 100 million years: Gravitational collapse: ordinary matter particles fall into the structures created by dark matter. Reionization begins: smaller (stars) and larger non-linear structures (quasars) begin to take shape – their ultraviolet light ionizes remaining neutral gas.
  • 200–300 million years: First stars begin to shine: Because many are Population III stars (some Population II stars are accounted for at this time) they are much bigger and hotter and their life cycle is fairly short. Unlike later generations of stars, these stars are metal free. Reionization begins, with the absorption of certain wavelengths of light by neutral hydrogen creating Gunn–Peterson troughs. The resulting ionized gas (especially free electrons) in the intergalactic medium causes some scattering of light, but with much lower opacity than before recombination due the expansion of the universe and clumping of gas into galaxies.
  • 200 million years: The oldest-known star (confirmed) – SMSS J031300.36−670839.3, forms.
  • 300 million years: First large-scale astronomical objects, protogalaxies and quasars may have begun forming. As Population III stars continue to burn, stellar nucleosynthesis operates – stars burn mainly by fusing hydrogen to produce more helium in what is referred to as the main sequence. Over time these stars are forced to fuse helium to produce carbon, oxygen, silicon and other heavy elements up to iron on the periodic table. These elements, when seeded into neighbouring gas clouds by supernova, will lead to the formation of more Population II stars (metal poor) and gas giants.
  • 320 million years (z = 13.3): HD1, the oldest-known spectroscopically-confirmed galaxy, forms.
  • 380 million years: UDFj-39546284 forms, current record holder for unconfirmed oldest-known quasar.
  • 600 million years: HE 1523-0901, the oldest star found producing neutron capture elements forms, marking a new point in ability to detect stars with a telescope.
  • 630 million years (z = 8.2): GRB 090423, the oldest gamma-ray burst recorded suggests that supernovas may have happened very early on in the evolution of the Universe

Galaxy epoch

  • < 1 billion years, (13 Gya): first stars in the central bar portion of the Milky Way are born,
  • 2.6 billion years (11 Gya): first stars in the thick disk region of the Milky Way are formed.
  • 4 billion years (10 Gya): Gaia Enceladus merges into Milky Way.
  • 5 or 6 billion years, (8 or 9 Gya): first stars in the thin disk region of the Milky Way are formed.

Acceleration

Notable cosmological and other events of the natural history depicted in a spiral. In the center left the primal supernova can be seen and continuing the creation of the Sun, the Earth and the Moon (by Theia impact) can be seen

Epochs of the formation of the Solar System

Main article: Formation and evolution of the Solar System
  • 9.2 billion years (4.6–4.57 Gya): Primal supernova, possibly triggers the formation of The Solar System.
  • 9.2318 billion years (4.5682 Gya): Sun forms – Planetary nebula begins accretion of planets.
  • 9.23283 billion years (4.56717–4.55717 Gya): Four Jovian planets (Jupiter, Saturn, Uranus, Neptune) evolve around the Sun.
  • 9.257 billion years (4.543–4.5 Gya): Solar System of Eight planets, four terrestrial (Mercury, Venus, Earth, Mars) evolve around the Sun. Because of accretion many smaller planets form orbits around the proto-Sun some with conflicting orbits – early heavy bombardment begins. A large planetoid strikes Mercury, stripping it of outer envelope of original crust and mantle, leaving the planet's core exposed – Mercury's iron content is notably high.
  • 9.266 billion years (4.533 Gya): Formation of Earth-Moon system following giant impact by hypothetical planetoid Theia (planet). Moon's gravitational pull helps stabilize Earth's fluctuating axis of rotation.
  • 9.271 billion years (4.529 Gya): Major collision with a pluto-sized planetoid establishes the Martian dichotomy on Mars
  • 9.3 billion years (4.5 Gya): Sun becomes a main sequence yellow star: formation of the Oort cloud and Kuiper belt
  • 9.396 billion years (4.404 Gya): Liquid water may have existed on the surface of the Earth
  • 9.7 billion years (4.1 Gya): Resonance in Jupiter and Saturn's orbits moves Neptune out into the Kuiper belt causing a disruption among asteroids and comets there. As a result, Late Heavy Bombardment batters the inner Solar System. Meteorite impact creates the Hellas Planitia on Mars, the largest unambiguous structure on the planet.
  • 10.4 billion years (3.5 Gya): Earliest fossil traces of life on Earth (stromatolites)
  • 10.6 billion years (3.2 Gya): Martian climate thins to its present density: groundwater stored in upper crust (megaregolith) begins to freeze, forming thick cryosphere overlying deeper zone of liquid water – dry ices composed of frozen carbon dioxide form
  • 10.8 billion years (3 Gya): Beethoven Basin forms on Mercury – unlike many basins of similar size on the Moon, Beethoven is not multi ringed and ejecta buries crater rim and is barely visible
  • 11.6 billion years (2.2 Gya): Last great tectonic period in Martian geologic history: Valles Marineris, largest canyon complex in the Solar System, forms – although some suggestions of thermokarst activity or even water erosion, it is suggested Valles Marineris is rift fault.

Recent history

  • 11.8 billion years (2 Gya): Olympus Mons, the largest volcano in the Solar System, is formed
  • 12.1 billion years (1.7 Gya): Sagittarius Dwarf Spheroidal Galaxy captured into an orbit around Milky Way Galaxy
  • 12.7 billion years (1.1 Gya): Copernican Period begins on Moon: defined by impact craters that possess bright optically immature ray systems
  • 12.8 billion years (1 Gya): Interactions between Andromeda and its companion galaxies Messier 32 and Messier 110. Galaxy collision with Messier 82 forms its patterned spiral disc: galaxy interactions between NGC 3077 and Messier 81; Saturn's moon Titan begins evolving the recognisable surface features that include rivers, lakes, and deltas
  • 13 billion years (800 Mya): Copernicus (lunar crater) forms from the impact on the Lunar surface in the area of Oceanus Procellarum – has terrace inner wall and 30 km wide, sloping rampart that descends nearly a kilometre to the surrounding mare
  • 13.175 billion years (625 Mya): formation of Hyades star cluster: consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical content and motion through space
  • 13.2 billion years (600 Mya): Whirlpool Galaxy collides with NGC 5195 forming a present connected galaxy system. HD 189733 b forms around parent star HD 189733: the first planet to reveal the climate, organic constituencies, even colour (blue) of its atmosphere
  • 13.6–13.5 billion years (300-200 Mya): Sirius, the brightest star in the Earth's sky, forms.
  • 13.7 billion years (100 Mya): Formation of Pleiades Star Cluster
  • 13.780 billion years (20 Mya): Possible formation of Orion Nebula
  • 13.792 billion years (7.6 Mya): Betelgeuse forms.
  • 13.8 billion years (Without uncertainties): Present day.
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