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From Wikipedia, the free encyclopedia
This article is about the theory. For the television series, see The Big Bang Theory. For other uses, see Big Bang (disambiguation) and Big Bang Theory (disambiguation).
A model of the expanding universe opening up from the viewer's left, facing the viewer in a 3/4 pose.
Timeline of the expansion of the universe, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates (artist's concept; neither time or size are to scale).
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The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature.[1] It was first proposed in 1927 by Roman Catholic priest and physicist Georges Lemaître. Various cosmological models of the Big Bang explain the evolution of the observable universe from the earliest known periods through its subsequent large-scale form.[2][3][4] These models offer a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure. The overall uniformity of the Universe, known as the flatness problem, is explained through cosmic inflation: a sudden and very rapid expansion of space during the earliest moments. However, physics currently lacks a widely accepted theory of quantum gravity that can successfully model the earliest conditions of the Big Bang.

Crucially, these models are compatible with the Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the models describe an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity").[5] In 1964 the CMB was discovered, which convinced many cosmologists that the competing steady-state model of cosmic evolution was falsified,[6] since the Big Bang models predict a uniform background radiation caused by high temperatures and densities in the distant past. A wide range of empirical evidence strongly favors the Big Bang event, which is now essentially universally accepted.[7] Detailed measurements of the expansion rate of the universe place the Big Bang singularity at an estimated 13.787±0.020 billion years ago, which is considered the age of the universe.[8]

There remain aspects of the observed universe that are not yet adequately explained by the Big Bang models. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. The unequal abundances of matter and antimatter that allowed this to occur is an unexplained effect known as baryon asymmetry. These primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies. Astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang models and various observations indicate that this excess gravitational potential is not created by baryonic matter, such as normal atoms. Measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to an unexplained phenomenon known as dark energy.[9]

Features of the models
The Big Bang models offer a comprehensive explanation for a broad range of observed phenomena, including the abundances of the light elements, the CMB, large-scale structure, and Hubble's law.[10] The models depend on two major assumptions: the universality of physical laws and the cosmological principle. The universality of physical laws is one of the underlying principles of the theory of relativity. The cosmological principle states that on large scales the universe is homogeneous and isotropic—appearing the same in all directions regardless of location.[11]

These ideas were initially taken as postulates, but later efforts were made to test each of them. For example, the first assumption has been tested by observations showing that the largest possible deviation of the fine-structure constant over much of the age of the universe is of order 10−5.[12] Also, general relativity has passed stringent tests on the scale of the Solar System and binary stars.[13][14][notes 1]

The large-scale universe appears isotropic as viewed from Earth. If it is indeed isotropic, the cosmological principle can be derived from the simpler Copernican principle, which states that there is no preferred (or special) observer or vantage point. To this end, the cosmological principle has been confirmed to a level of 10−5 via observations of the temperature of the CMB. At the scale of the CMB horizon, the universe has been measured to be homogeneous with an upper bound on the order of 10% inhomogeneity, as of 1995.[15]

Horizons
Main article: Cosmological horizon
An important feature of the Big Bang spacetime is the presence of particle horizons. Since the universe has a finite age, and light travels at a finite speed, there may be events in the past whose light has not yet had time to reach earth. This places a limit or a past horizon on the most distant objects that can be observed. Conversely, because space is expanding, and more distant objects are receding ever more quickly, light emitted by us today may never "catch up" to very distant objects. This defines a future horizon, which limits the events in the future that we will be able to influence. The presence of either type of horizon depends on the details of the FLRW model that describes our universe.[16]

Our understanding of the universe back to very early times suggests that there is a past horizon, though in practice our view is also limited by the opacity of the universe at early times. So our view cannot extend further backward in time, though the horizon recedes in space. If the expansion of the universe continues to accelerate, there is a future horizon as well.[16]

Thermalization
Some processes in the early universe occurred too slowly, compared to the expansion rate of the universe, to reach approximate thermodynamic equilibrium. Others were fast enough to reach thermalization. The parameter usually used to find out whether a process in the very early universe has reached thermal equilibrium is the ratio between the rate of the process (usually rate of collisions between particles) and the Hubble parameter. The larger the ratio, the more time particles had to thermalize before they were too far away from each other.[17]

Timeline
Main article: Chronology of the universe
External Timeline	A graphical timeline is available at
Graphical timeline of the Big Bang
According to the Big Bang models, the universe at the beginning was very hot and very compact, and since then it has been expanding and cooling.

Singularity
See also: Gravitational singularity, Initial singularity, and Planck units § Cosmology
Extrapolation of the expansion of the universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past.[18] This irregular behavior, known as the gravitational singularity, indicates that general relativity is not an adequate description of the laws of physics in this regime. Models based on general relativity alone cannot fully extrapolate toward the singularity.[5] In some proposals, such as the emergent Universe models, the singularity is replaced by another cosmological epoch. A different approach identifies the initial singularity as a singularity predicted by some models of the Big Bang theory to have existed before the Big Bang.[19][clarification needed]

This primordial singularity is itself sometimes called "the Big Bang",[20] but the term can also refer to a more generic early hot, dense phase[21][notes 2] of the universe. In either case, "the Big Bang" as an event is also colloquially referred to as the "birth" of our universe since it represents the point in history where the universe can be verified to have entered into a regime where the laws of physics as we understand them (specifically general relativity and the Standard Model of particle physics) work. Based on measurements of the expansion using Type Ia supernovae and measurements of temperature fluctuations in the cosmic microwave background, the time that has passed since that event—known as the "age of the universe"—is 13.8 billion years.[22]

Despite being extremely dense at this time—far denser than is usually required to form a black hole—the universe did not re-collapse into a singularity. Commonly used calculations and limits for explaining gravitational collapse are usually based upon objects of relatively constant size, such as stars, and do not apply to rapidly expanding space such as the Big Bang. Since the early universe did not immediately collapse into a multitude of black holes, matter at that time must have been very evenly distributed with a negligible density gradient.[23]

Inflation and baryogenesis
Main articles: Inflation (cosmology) and Baryogenesis
The earliest phases of the Big Bang are subject to much speculation, since astronomical data about them are not available. In the most common models the universe was filled homogeneously and isotropically with a very high energy density and huge temperatures and pressures, and was very rapidly expanding and cooling. The period up to 10−43 seconds into the expansion, the Planck epoch, was a phase in which the four fundamental forces—the electromagnetic force, the strong nuclear force, the weak nuclear force, and the gravitational force, were unified as one.[24] In this stage, the characteristic scale length of the universe was the Planck length, 1.6×10−35 m, and consequently had a temperature of approximately 1032 degrees Celsius. Even the very concept of a particle breaks down in these conditions. A proper understanding of this period awaits the development of a theory of quantum gravity.[25][26] The Planck epoch was succeeded by the grand unification epoch beginning at 10−43 seconds, where gravitation separated from the other forces as the universe's temperature fell.[24]

At approximately 10−37 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially, unconstrained by the light speed invariance, and temperatures dropped by a factor of 100,000. This concept is motivated by the flatness problem, where the density of matter and energy is very close to the critical density needed to produce a flat universe. That is, the shape of the universe has no overall geometric curvature due to gravitational influence. Microscopic quantum fluctuations that occurred because of Heisenberg's uncertainty principle were "frozen in" by inflation, becoming amplified into the seeds that would later form the large-scale structure of the universe.[27] At a time around 10−36 seconds, the electroweak epoch begins when the strong nuclear force separates from the other forces, with only the electromagnetic force and weak nuclear force remaining unified.[28]

Inflation stopped locally at around 10−33 to 10−32 seconds, with the observable universe's volume having increased by a factor of at least 1078. Reheating occurred until the universe obtained the temperatures required for the production of a quark–gluon plasma as well as all other elementary particles.[29][30] Temperatures were so high that the random motions of particles were at relativistic speeds, and particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions.[1] At some point, an unknown reaction called baryogenesis violated the conservation of baryon number, leading to a very small excess of quarks and leptons over antiquarks and antileptons—of the order of one part in 30 million. This resulted in the predominance of matter over antimatter in the present universe.[31]

Cooling
Main articles: Big Bang nucleosynthesis and Cosmic microwave background
A map of the universe, with specks and strands of light of different colors.
Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. Galaxies are color-coded by redshift.
The universe continued to decrease in density and fall in temperature, hence the typical energy of each particle was decreasing. Symmetry-breaking phase transitions put the fundamental forces of physics and the parameters of elementary particles into their present form, with the electromagnetic force and weak nuclear force separating at about 10−12 seconds.[28][32]

After about 10−11 seconds, the picture becomes less speculative, since particle energies drop to values that can be attained in particle accelerators. At about 10−6 seconds, quarks and gluons combined to form baryons such as protons and neutrons. The small excess of quarks over antiquarks led to a small excess of baryons over antibaryons. The temperature was no longer high enough to create either new proton–antiproton or neutron–antineutron pairs. A mass annihilation immediately followed, leaving just one in 108 of the original matter particles and none of their antiparticles.[33] A similar process happened at about 1 second for electrons and positrons. After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistically and the energy density of the universe was dominated by photons (with a minor contribution from neutrinos).

A few minutes into the expansion, when the temperature was about a billion kelvin and the density of matter in the universe was comparable to the current density of Earth's atmosphere, neutrons combined with protons to form the universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis (BBN).[34] Most protons remained uncombined as hydrogen nuclei.[35]

As the universe cooled, the rest energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years, the electrons and nuclei combined into atoms (mostly hydrogen), which were able to emit radiation. This relic radiation, which continued through space largely unimpeded, is known as the cosmic microwave background.[35]

Structure formation
Main article: Structure formation

Abell 2744 galaxy cluster – Hubble Frontier Fields view[36]
Over a long period of time, the slightly denser regions of the uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today.[1] The details of this process depend on the amount and type of matter in the universe. The four possible types of matter are known as cold dark matter (CDM), warm dark matter, hot dark matter, and baryonic matter. The best measurements available, from the Wilkinson Microwave Anisotropy Probe (WMAP), show that the data is well-fit by a Lambda-CDM model in which dark matter is assumed to be cold. (Warm dark matter is ruled out by early reionization.)[37] This CDM is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[38]

In an "extended model" which includes hot dark matter in the form of neutrinos,[39] then the "physical baryon density" 
Ω
b
ℎ
2
{\displaystyle \Omega _{\text{b}}h^{2}} is estimated at 0.023. (This is different from the 'baryon density' 
Ω
b
{\displaystyle \Omega _{\text{b}}} expressed as a fraction of the total matter/energy density, which is about 0.046.) The corresponding cold dark matter density 
Ω
c
ℎ
2
{\displaystyle \Omega _{\text{c}}h^{2}} is about 0.11, and the corresponding neutrino density 
Ω
v
ℎ
2
{\displaystyle \Omega _{\text{v}}h^{2}} is estimated to be less than 0.0062.[38]

Cosmic acceleration
Main article: Accelerating expansion of the universe
Independent lines of evidence from Type Ia supernovae and the CMB imply that the universe today is dominated by a mysterious form of energy known as dark energy, which appears to homogeneously permeate all of space. Observations suggest that 73% of the total energy density of the present day universe is in this form. When the universe was very young it was likely infused with dark energy, but with everything closer together, gravity predominated, braking the expansion. Eventually, after billions of years of expansion, the declining density of matter relative to the density of dark energy allowed the expansion of the universe to begin to accelerate.[9]

Dark energy in its simplest formulation is modeled by a cosmological constant term in Einstein field equations of general relativity, but its composition and mechanism are unknown. More generally, the details of its equation of state and relationship with the Standard Model of particle physics continue to be investigated both through observation and theory.[9]

All of this cosmic evolution after the inflationary epoch can be rigorously described and modeled by the lambda-CDM model of cosmology, which uses the independent frameworks of quantum mechanics and general relativity. There are no easily testable models that would describe the situation prior to approximately 10−15 seconds.[40] Understanding this earliest of eras in the history of the universe is one of the greatest unsolved problems in physics.

Concept history
Main article: History of the Big Bang theory
See also: Timeline of cosmological theories
Etymology
English astronomer Fred Hoyle is credited with coining the term "Big Bang" during a talk for a March 1949 BBC Radio broadcast,[41] saying: "These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past."[42][43] However, it did not catch on until the 1970s.[43]

It is popularly reported that Hoyle, who favored an alternative "steady-state" cosmological model, intended this to be pejorative,[44][45][46] but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models.[47][48][50] Helge Kragh writes that the evidence for the claim that it was meant as a pejorative is "unconvincing", and mentions a number of indications that it was not a pejorative.[43]

The term itself has been argued to be a misnomer because it evokes an explosion.[43][51] The argument is that whereas an explosion suggests expansion into a surrounding space, the Big Bang only describes the intrinsic expansion of the contents of the universe.[52][53] Another issue pointed out by Santhosh Mathew is that bang implies sound, which is not an important feature of the model.[45] An attempt to find a more suitable alternative was not successful.[43][46]

Development
Hubble eXtreme Deep Field (XDF)

XDF size compared to the size of the Moon (XDF is the small box to the left of, and nearly below, the Moon) – several thousand galaxies, each consisting of billions of stars, are in this small view.

XDF (2012) view – each light speck is a galaxy – some of these are as old as 13.2 billion years[55] – the universe is estimated to contain 200 billion galaxies.

XDF image shows fully mature galaxies in the foreground plane – nearly mature galaxies from 5 to 9 billion years ago – protogalaxies, blazing with young stars, beyond 9 billion years.
The Big Bang models developed from observations of the structure of the universe and from theoretical considerations. In 1912, Vesto Slipher measured the first Doppler shift of a "spiral nebula" (spiral nebula is the obsolete term for spiral galaxies), and soon discovered that almost all such nebulae were receding from Earth. He did not grasp the cosmological implications of this fact, and indeed at the time it was highly controversial whether or not these nebulae were "island universes" outside our Milky Way.[56][57] Ten years later, Alexander Friedmann, a Russian cosmologist and mathematician, derived the Friedmann equations from the Einstein field equations, showing that the universe might be expanding in contrast to the static universe model advocated by Albert Einstein at that time.[58]

In 1924, American astronomer Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies. Starting that same year, Hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2.5 m) Hooker telescope at Mount Wilson Observatory. This allowed him to estimate distances to galaxies whose redshifts had already been measured, mostly by Slipher. In 1929, Hubble discovered a correlation between distance and recessional velocity—now known as Hubble's law.[59][60]

Independently deriving Friedmann's equations in 1927, Georges Lemaître, a Belgian physicist and Roman Catholic priest, proposed that the recession of the nebulae was due to the expansion of the universe.[61] He inferred the relation that Hubble would later observe, given the cosmological principle.[9] In 1931, Lemaître went further and suggested that the evident expansion of the universe, if projected back in time, meant that the further in the past the smaller the universe was, until at some finite time in the past all the mass of the universe was concentrated into a single point, a "primeval atom" where and when the fabric of time and space came into existence.[62]

In the 1920s and 1930s, almost every major cosmologist preferred an eternal steady-state universe, and several complained that the beginning of time implied by the Big Bang imported religious concepts into physics; this objection was later repeated by supporters of the steady-state theory.[63] This perception was enhanced by the fact that the originator of the Big Bang concept, Lemaître, was a Roman Catholic priest.[64] Arthur Eddington agreed with Aristotle that the universe did not have a beginning in time, viz., that matter is eternal. A beginning in time was "repugnant" to him.[65][66] Lemaître, however, disagreed:

If the world has begun with a single quantum, the notions of space and time would altogether fail to have any meaning at the beginning; they would only begin to have a sensible meaning when the original quantum had been divided into a sufficient number of quanta. If this suggestion is correct, the beginning of the world happened a little before the beginning of space and time.[67]

During the 1930s, other ideas were proposed as non-standard cosmologies to explain Hubble's observations, including the Milne model,[68] the oscillatory universe (originally suggested by Friedmann, but advocated by Albert Einstein and Richard C. Tolman)[69] and Fritz Zwicky's tired light hypothesis.[70]

After World War II, two distinct possibilities emerged. One was Fred Hoyle's steady-state model, whereby new matter would be created as the universe seemed to expand. In this model the universe is roughly the same at any point in time.[71] The other was Lemaître's Big Bang theory, advocated and developed by George Gamow, who introduced BBN[72] and whose associates, Ralph Alpher and Robert Herman, predicted the CMB.[73] Ironically, it was Hoyle who coined the phrase that came to be applied to Lemaître's theory, referring to it as "this big bang idea" during a BBC Radio broadcast in March 1949.[48][43][notes 3] For a while, support was split between these two theories. Eventually, the observational evidence, most notably from radio source counts, began to favor Big Bang over steady state. The discovery and confirmation of the CMB in 1964 secured the Big Bang as the best theory of the origin and evolution of the universe.[74]

In 1968 and 1970, Roger Penrose, Stephen Hawking, and George F. R. Ellis published papers where they showed that mathematical singularities were an inevitable initial condition of relativistic models of the Big Bang.[75][76] Then, from the 1970s to the 1990s, cosmologists worked on characterizing the features of the Big Bang universe and resolving outstanding problems. In 1981, Alan Guth made a breakthrough in theoretical work on resolving certain outstanding theoretical problems in the Big Bang models with the introduction of an epoch of rapid expansion in the early universe he called "inflation".[77] Meanwhile, during these decades, two questions in observational cosmology that generated much discussion and disagreement were over the precise values of the Hubble Constant[78] and the matter-density of the universe (before the discovery of dark energy, thought to be the key predictor for the eventual fate of the universe).[79]

In the mid-1990s, observations of certain globular clusters appeared to indicate that they were about 15 billion years old, which conflicted with most then-current estimates of the age of the universe (and indeed with the age measured today). This issue was later resolved when new computer simulations, which included the effects of mass loss due to stellar winds, indicated a much younger age for globular clusters.[80]

Significant progress in Big Bang cosmology has been made since the late 1990s as a result of advances in telescope technology as well as the analysis of data from satellites such as the Cosmic Background Explorer (COBE),[81] the Hubble Space Telescope and WMAP.[82] Cosmologists now have fairly precise and accurate measurements of many of the parameters of the Big Bang model, and have made the unexpected discovery that the expansion of the universe appears to be accelerating.[83][84]

Observational evidence
"[The] big bang picture is too firmly grounded in data from every area to be proved invalid in its general features."

— Lawrence Krauss[85]
The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang nucleosynthesis (BBN). More recent evidence includes observations of galaxy formation and evolution, and the distribution of large-scale cosmic structures,[86] These are sometimes called the "four pillars" of the Big Bang models.[87]

Precise modern models of the Big Bang appeal to various exotic physical phenomena that have not been observed in terrestrial laboratory experiments or incorporated into the Standard Model of particle physics. Of these features, dark matter is currently the subject of most active laboratory investigations.[88] Remaining issues include the cuspy halo problem[89] and the dwarf galaxy problem[90] of cold dark matter. Dark energy is also an area of intense interest for scientists, but it is not clear whether direct detection of dark energy will be possible.[91] Inflation and baryogenesis remain more speculative features of current Big Bang models. Viable, quantitative explanations for such phenomena are still being sought. These are unsolved problems in physics.


Hubble's law and the expansion of the universe
Main articles: Hubble's law and Expansion of the universe
See also: Distance measures (cosmology) and Scale factor (cosmology)
Observations of distant galaxies and quasars show that these objects are redshifted: the light emitted from them has been shifted to longer wavelengths. This can be seen by taking a frequency spectrum of an object and matching the spectroscopic pattern of emission or absorption lines corresponding to atoms of the chemical elements interacting with the light. These redshifts are uniformly isotropic, distributed evenly among the observed objects in all directions. If the redshift is interpreted as a Doppler shift, the recessional velocity of the object can be calculated. For some galaxies, it is possible to estimate distances via the cosmic distance ladder. When the recessional velocities are plotted against these distances, a linear relationship known as Hubble's law is observed:[59] 
�
=
�
0
�
{\displaystyle v=H_{0}D} where

�
v is the recessional velocity of the galaxy or other distant object,
�
D is the proper distance to the object, and
�
0
H_{0} is Hubble's constant, measured to be 70.4+1.3
−1.4 km/s/Mpc by the WMAP.[38]
Hubble's law implies that the universe is uniformly expanding everywhere. This cosmic expansion was predicted from general relativity by Friedmann in 1922[58] and Lemaître in 1927,[61] well before Hubble made his 1929 analysis and observations, and it remains the cornerstone of the Big Bang model as developed by Friedmann, Lemaître, Robertson, and Walker.

The theory requires the relation 
�
=
�
�
{\displaystyle v=HD} to hold at all times, where 
�
D is the proper distance, v is the recessional velocity, and 
�
v, 
�
H, and 
�
D vary as the universe expands (hence we write 
�
0
H_{0} to denote the present-day Hubble "constant"). For distances much smaller than the size of the observable universe, the Hubble redshift can be thought of as the Doppler shift corresponding to the recession velocity 
�
v. For distances comparable to the size of the observable universe, the attribution of the cosmological redshift becomes more ambiguous, although its interpretation as a kinematic Doppler shift remains the most natural one.[92]

An unexplained discrepancy with the determination of the Hubble constant is known as Hubble tension. Techniques based on observation of the CMB suggest a lower value of this constant compared to the quantity derived from measurements based on the cosmic distance ladder.[93]

Cosmic microwave background radiation
Main article: Cosmic microwave background

The cosmic microwave background spectrum measured by the FIRAS instrument on the COBE satellite is the most-precisely measured blackbody spectrum in nature.[94] The data points and error bars on this graph are obscured by the theoretical curve.
In 1964, Arno Penzias and Robert Wilson serendipitously discovered the cosmic background radiation, an omnidirectional signal in the microwave band.[74] Their discovery provided substantial confirmation of the big-bang predictions by Alpher, Herman and Gamow around 1950. Through the 1970s, the radiation was found to be approximately consistent with a blackbody spectrum in all directions; this spectrum has been redshifted by the expansion of the universe, and today corresponds to approximately 2.725 K. This tipped the balance of evidence in favor of the Big Bang model, and Penzias and Wilson were awarded the 1978 Nobel Prize in Physics.

The surface of last scattering corresponding to emission of the CMB occurs shortly after recombination, the epoch when neutral hydrogen becomes stable. Prior to this, the universe comprised a hot dense photon-baryon plasma sea where photons were quickly scattered from free charged particles. Peaking at around 372±14 kyr,[37] the mean free path for a photon becomes long enough to reach the present day and the universe becomes transparent.


9 year WMAP image of the cosmic microwave background radiation (2012).[95][96] The radiation is isotropic to roughly one part in 100,000.[97]
In 1989, NASA launched COBE, which made two major advances: in 1990, high-precision spectrum measurements showed that the CMB frequency spectrum is an almost perfect blackbody with no deviations at a level of 1 part in 104, and measured a residual temperature of 2.726 K (more recent measurements have revised this figure down slightly to 2.7255 K); then in 1992, further COBE measurements discovered tiny fluctuations (anisotropies) in the CMB temperature across the sky, at a level of about one part in 105.[81] John C. Mather and George Smoot were awarded the 2006 Nobel Prize in Physics for their leadership in these results.

During the following decade, CMB anisotropies were further investigated by a large number of ground-based and balloon experiments. In 2000–2001, several experiments, most notably BOOMERanG, found the shape of the universe to be spatially almost flat by measuring the typical angular size (the size on the sky) of the anisotropies.[98][99][100]

In early 2003, the first results of the Wilkinson Microwave Anisotropy Probe were released, yielding what were at the time the most accurate values for some of the cosmological parameters. The results disproved several specific cosmic inflation models, but are consistent with the inflation theory in general.[82] The Planck space probe was launched in May 2009. Other ground and balloon-based cosmic microwave background experiments are ongoing.

Abundance of primordial elements
Main article: Big Bang nucleosynthesis
Using Big Bang models, it is possible to calculate the expected concentration of the isotopes helium-4 (4He), helium-3 (3He), deuterium (2H), and lithium-7 (7Li) in the universe as ratios to the amount of ordinary hydrogen.[34] The relative abundances depend on a single parameter, the ratio of photons to baryons. This value can be calculated independently from the detailed structure of CMB fluctuations. The ratios predicted (by mass, not by abundance) are about 0.25 for 4He:H, about 10−3 for 2H:H, about 10−4 for 3He:H, and about 10−9 for 7Li:H.[34]

The measured abundances all agree at least roughly with those predicted from a single value of the baryon-to-photon ratio. The agreement is excellent for deuterium, close but formally discrepant for 4He, and off by a factor of two for 7Li (this anomaly is known as the cosmological lithium problem); in the latter two cases, there are substantial systematic uncertainties. Nonetheless, the general consistency with abundances predicted by BBN is strong evidence for the Big Bang, as the theory is the only known explanation for the relative abundances of light elements, and it is virtually impossible to "tune" the Big Bang to produce much more or less than 20–30% helium.[101] Indeed, there is no obvious reason outside of the Big Bang that, for example, the young universe before star formation, as determined by studying matter supposedly free of stellar nucleosynthesis products, should have more helium than deuterium or more deuterium than 3He, and in constant ratios, too.[102]: 182–185 

Galactic evolution and distribution
Main articles: Galaxy formation and evolution and Structure formation
Detailed observations of the morphology and distribution of galaxies and quasars are in agreement with the current Big Bang models. A combination of observations and theory suggest that the first quasars and galaxies formed within a billion years after the Big Bang,[103] and since then, larger structures have been forming, such as galaxy clusters and superclusters.[104]

Populations of stars have been aging and evolving, so that distant galaxies (which are observed as they were in the early universe) appear very different from nearby galaxies (observed in a more recent state). Moreover, galaxies that formed relatively recently, appear markedly different from galaxies formed at similar distances but shortly after the Big Bang. These observations are strong arguments against the steady-state model. Observations of star formation, galaxy and quasar distributions and larger structures, agree well with Big Bang simulations of the formation of structure in the universe, and are helping to complete details of the theory.[104][105]

Primordial gas clouds

Focal plane of BICEP2 telescope under a microscope – used to search for polarization in the CMB[106][107][108][109]
In 2011, astronomers found what they believe to be pristine clouds of primordial gas by analyzing absorption lines in the spectra of distant quasars. Before this discovery, all other astronomical objects have been observed to contain heavy elements that are formed in stars. Despite being sensitive to carbon, oxygen, and silicon, these three elements were not detected in these two clouds.[110][111] Since the clouds of gas have no detectable levels of heavy elements, they likely formed in the first few minutes after the Big Bang, during BBN.

Other lines of evidence
The age of the universe as estimated from the Hubble expansion and the CMB is now in agreement with other estimates using the ages of the oldest stars, both as measured by applying the theory of stellar evolution to globular clusters and through radiometric dating of individual Population II stars.[112] It is also in agreement with age estimates based on measurements of the expansion using Type Ia supernovae and measurements of temperature fluctuations in the cosmic microwave background.[22] The agreement of independent measurements of this age supports the Lambda-CDM (ΛCDM) model, since the model is used to relate some of the measurements to an age estimate, and all estimates turn agree. Still, some observations of objects from the relatively early universe (in particular quasar APM 08279+5255) raise concern as to whether these objects had enough time to form so early in the ΛCDM model.[113][114]

The prediction that the CMB temperature was higher in the past has been experimentally supported by observations of very low temperature absorption lines in gas clouds at high redshift.[115] This prediction also implies that the amplitude of the Sunyaev–Zel'dovich effect in clusters of galaxies does not depend directly on redshift. Observations have found this to be roughly true, but this effect depends on cluster properties that do change with cosmic time, making precise measurements difficult.[116][117]

Future observations
Future gravitational-wave observatories might be able to detect primordial gravitational waves, relics of the early universe, up to less than a second after the Big Bang.[118][119]

Problems and related issues in physics
See also: List of unsolved problems in physics
As with any theory, a number of mysteries and problems have arisen as a result of the development of the Big Bang models. Some of these mysteries and problems have been resolved while others are still outstanding. Proposed solutions to some of the problems in the Big Bang model have revealed new mysteries of their own. For example, the horizon problem, the magnetic monopole problem, and the flatness problem are most commonly resolved with inflation theory, but the details of the inflationary universe are still left unresolved and many, including some founders of the theory, say it has been disproven.[120][121][122][123] What follows are a list of the mysterious aspects of the Big Bang concept still under intense investigation by cosmologists and astrophysicists.

Baryon asymmetry
Main article: Baryon asymmetry
It is not yet understood why the universe has more matter than antimatter.[31] It is generally assumed that when the universe was young and very hot it was in statistical equilibrium and contained equal numbers of baryons and antibaryons. However, observations suggest that the universe, including its most distant parts, is made almost entirely of normal matter, rather than antimatter. A process called baryogenesis was hypothesized to account for the asymmetry. For baryogenesis to occur, the Sakharov conditions must be satisfied. These require that baryon number is not conserved, that C-symmetry and CP-symmetry are violated and that the universe depart from thermodynamic equilibrium.[124] All these conditions occur in the Standard Model, but the effects are not strong enough to explain the present baryon asymmetry.

Dark energy
Main article: Dark energy
Measurements of the redshift–magnitude relation for type Ia supernovae indicate that the expansion of the universe has been accelerating since the universe was about half its present age. To explain this acceleration, general relativity requires that much of the energy in the universe consists of a component with large negative pressure, dubbed "dark energy".[9]

Dark energy, though speculative, solves numerous problems. Measurements of the cosmic microwave background indicate that the universe is very nearly spatially flat, and therefore according to general relativity the universe must have almost exactly the critical density of mass/energy. But the mass density of the universe can be measured from its gravitational clustering, and is found to have only about 30% of the critical density.[9] Since theory suggests that dark energy does not cluster in the usual way it is the best explanation for the "missing" energy density. Dark energy also helps to explain two geometrical measures of the overall curvature of the universe, one using the frequency of gravitational lenses,[125] and the other using the characteristic pattern of the large-scale structure as a cosmic ruler.[citation needed]

Negative pressure is believed to be a property of vacuum energy, but the exact nature and existence of dark energy remains one of the great mysteries of the Big Bang. Results from the WMAP team in 2008 are in accordance with a universe that consists of 73% dark energy, 23% dark matter, 4.6% regular matter and less than 1% neutrinos.[38] According to theory, the energy density in matter decreases with the expansion of the universe, but the dark energy density remains constant (or nearly so) as the universe expands. Therefore, matter made up a larger fraction of the total energy of the universe in the past than it does today, but its fractional contribution will fall in the far future as dark energy becomes even more dominant.[citation needed]

The dark energy component of the universe has been explained by theorists using a variety of competing theories including Einstein's cosmological constant but also extending to more exotic forms of quintessence or other modified gravity schemes.[126] A cosmological constant problem, sometimes called the "most embarrassing problem in physics", results from the apparent discrepancy between the measured energy density of dark energy, and the one naively predicted from Planck units.[127]

Dark matter
Main article: Dark matter

Chart shows the proportion of different components of the universe  – about 95% is dark matter and dark energy.
During the 1970s and the 1980s, various observations showed that there is not sufficient visible matter in the universe to account for the apparent strength of gravitational forces within and between galaxies. This led to the idea that up to 90% of the matter in the universe is dark matter that does not emit light or interact with normal baryonic matter. In addition, the assumption that the universe is mostly normal matter led to predictions that were strongly inconsistent with observations. In particular, the universe today is far more lumpy and contains far less deuterium than can be accounted for without dark matter. While dark matter has always been controversial, it is inferred by various observations: the anisotropies in the CMB, galaxy cluster velocity dispersions, large-scale structure distributions, gravitational lensing studies, and X-ray measurements of galaxy clusters.[128]

Indirect evidence for dark matter comes from its gravitational influence on other matter, as no dark matter particles have been observed in laboratories. Many particle physics candidates for dark matter have been proposed, and several projects to detect them directly are underway.[129]

Additionally, there are outstanding problems associated with the currently favored cold dark matter model which include the dwarf galaxy problem[90] and the cuspy halo problem.[89] Alternative theories have been proposed that do not require a large amount of undetected matter, but instead modify the laws of gravity established by Newton and Einstein; yet no alternative theory has been as successful as the cold dark matter proposal in explaining all extant observations.[130]

Horizon problem
Main article: Horizon problem
The horizon problem results from the premise that information cannot travel faster than light. In a universe of finite age this sets a limit—the particle horizon—on the separation of any two regions of space that are in causal contact.[131] The observed isotropy of the CMB is problematic in this regard: if the universe had been dominated by radiation or matter at all times up to the epoch of last scattering, the particle horizon at that time would correspond to about 2 degrees on the sky. There would then be no mechanism to cause wider regions to have the same temperature.[102]: 191–202 

A resolution to this apparent inconsistency is offered by inflation theory in which a homogeneous and isotropic scalar energy field dominates the universe at some very early period (before baryogenesis). During inflation, the universe undergoes exponential expansion, and the particle horizon expands much more rapidly than previously assumed, so that regions presently on opposite sides of the observable universe are well inside each other's particle horizon. The observed isotropy of the CMB then follows from the fact that this larger region was in causal contact before the beginning of inflation.[27]: 180–186 

Heisenberg's uncertainty principle predicts that during the inflationary phase there would be quantum thermal fluctuations, which would be magnified to a cosmic scale. These fluctuations served as the seeds for all the current structures in the universe.[102]: 207  Inflation predicts that the primordial fluctuations are nearly scale invariant and Gaussian, which has been confirmed by measurements of the CMB.[82]: sec 6 

A related issue to the classic horizon problem arises because in most standard cosmological inflation models, inflation ceases well before electroweak symmetry breaking occurs, so inflation should not be able to prevent large-scale discontinuities in the electroweak vacuum since distant parts of the observable universe were causally separate when the electroweak epoch ended.[132]

Magnetic monopoles
The magnetic monopole objection was raised in the late 1970s. Grand unified theories (GUTs) predicted topological defects in space that would manifest as magnetic monopoles. These objects would be produced efficiently in the hot early universe, resulting in a density much higher than is consistent with observations, given that no monopoles have been found. This problem is resolved by cosmic inflation, which removes all point defects from the observable universe, in the same way that it drives the geometry to flatness.[131]

Flatness problem

The overall geometry of the universe is determined by whether the Omega cosmological parameter is less than, equal to or greater than 1. Shown from top to bottom are a closed universe with positive curvature, a hyperbolic universe with negative curvature and a flat universe with zero curvature.
The flatness problem (also known as the oldness problem) is an observational problem associated with a FLRW.[131] The universe may have positive, negative, or zero spatial curvature depending on its total energy density. Curvature is negative if its density is less than the critical density; positive if greater; and zero at the critical density, in which case space is said to be flat. Observations indicate the universe is consistent with being flat.[133][134]

The problem is that any small departure from the critical density grows with time, and yet the universe today remains very close to flat.[notes 4] Given that a natural timescale for departure from flatness might be the Planck time, 10−43 seconds,[1] the fact that the universe has reached neither a heat death nor a Big Crunch after billions of years requires an explanation. For instance, even at the relatively late age of a few minutes (the time of nucleosynthesis), the density of the universe must have been within one part in 1014 of its critical value, or it would not exist as it does today.[135]

Misconceptions
One of the common misconceptions about the Big Bang model is that it fully explains the origin of the universe. However, the Big Bang model does not describe how energy, time, and space were caused, but rather it describes the emergence of the present universe from an ultra-dense and high-temperature initial state.[136] It is misleading to visualize the Big Bang by comparing its size to everyday objects. When the size of the universe at Big Bang is described, it refers to the size of the observable universe, and not the entire universe.[137]

Another common misconception is that the Big Bang must be understood as the expansion of space and not in terms of the contents of space exploding apart. In fact, either description can be accurate. The expansion of space (implied by the FLRW metric) is only a mathematical convention, corresponding to a choice of coordinates on spacetime. There is no generally covariant sense in which space expands.[138]

The recession speeds associated with Hubble's law are not velocities in a relativistic sense (for example, they are not related to the spatial components of 4-velocities). Therefore, it is not remarkable that according to Hubble's law, galaxies farther than the Hubble distance recede faster than the speed of light. Such recession speeds do not correspond to faster-than-light travel.

Many popular accounts attribute the cosmological redshift to the expansion of space. This can be misleading because the expansion of space is only a coordinate choice. The most natural interpretation of the cosmological redshift is that it is a Doppler shift.[92]

Implications
Given current understanding, scientific extrapolations about the future of the universe are only possible for finite durations, albeit for much longer periods than the current age of the universe. Anything beyond that becomes increasingly speculative. Likewise, at present, a proper understanding of the origin of the universe can only be subject to conjecture.[139]

Pre–Big Bang cosmology
The Big Bang explains the evolution of the universe from a starting density and temperature that is well beyond humanity's capability to replicate, so extrapolations to the most extreme conditions and earliest times are necessarily more speculative. Lemaître called this initial state the "primeval atom" while Gamow called the material "ylem". How the initial state of the universe originated is still an open question, but the Big Bang model does constrain some of its characteristics. For example, specific laws of nature most likely came to existence in a random way, but as inflation models show, some combinations of these are far more probable.[140] A flat universe implies a balance between gravitational potential energy and other energy forms, requiring no additional energy to be created.[133][134]

The Big Bang theory, built upon the equations of classical general relativity, indicates a singularity at the origin of cosmic time, and such an infinite energy density may be a physical impossibility. However, the physical theories of general relativity and quantum mechanics as currently realized are not applicable before the Planck epoch, and correcting this will require the development of a correct treatment of quantum gravity.[18] Certain quantum gravity treatments, such as the Wheeler–DeWitt equation, imply that time itself could be an emergent property.[141] As such, physics may conclude that time did not exist before the Big Bang.[142][143]

While it is not known what could have preceded the hot dense state of the early universe or how and why it originated, or even whether such questions are sensible, speculation abounds on the subject of "cosmogony".

Some speculative proposals in this regard, each of which entails untested hypotheses, are:

The simplest models, in which the Big Bang was caused by quantum fluctuations. That scenario had very little chance of happening, but, according to the totalitarian principle, even the most improbable event will eventually happen. It took place instantly, in our perspective, due to the absence of perceived time before the Big Bang.[144][145][146][147]
Emergent Universe models, which feature a low-activity past-eternal era before the Big Bang, resembling ancient ideas of a cosmic egg and birth of the world out of primordial chaos.
Models in which the whole of spacetime is finite, including the Hartle–Hawking no-boundary condition. For these cases, the Big Bang does represent the limit of time but without a singularity.[148] In such a case, the universe is self-sufficient.[149]
Brane cosmology models, in which inflation is due to the movement of branes in string theory; the pre-Big Bang model; the ekpyrotic model, in which the Big Bang is the result of a collision between branes; and the cyclic model, a variant of the ekpyrotic model in which collisions occur periodically. In the latter model the Big Bang was preceded by a Big Crunch and the universe cycles from one process to the other.[150][151][152][153]
Eternal inflation, in which universal inflation ends locally here and there in a random fashion, each end-point leading to a bubble universe, expanding from its own big bang.[154][155]
Proposals in the last two categories see the Big Bang as an event in either a much larger and older universe or in a multiverse.

Ultimate fate of the universe
Main article: Ultimate fate of the universe
Before observations of dark energy, cosmologists considered two scenarios for the future of the universe. If the mass density of the universe were greater than the critical density, then the universe would reach a maximum size and then begin to collapse. It would become denser and hotter again, ending with a state similar to that in which it started—a Big Crunch.[16]

Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. Star formation would cease with the consumption of interstellar gas in each galaxy; stars would burn out, leaving white dwarfs, neutron stars, and black holes. Collisions between these would result in mass accumulating into larger and larger black holes. The average temperature of the universe would very gradually asymptotically approach absolute zero—a Big Freeze.[156] Moreover, if protons are unstable, then baryonic matter would disappear, leaving only radiation and black holes. Eventually, black holes would evaporate by emitting Hawking radiation. The entropy of the universe would increase to the point where no organized form of energy could be extracted from it, a scenario known as heat death.[157]

Modern observations of accelerating expansion imply that more and more of the currently visible universe will pass beyond our event horizon and out of contact with us. The eventual result is not known. The ΛCDM model of the universe contains dark energy in the form of a cosmological constant. This theory suggests that only gravitationally bound systems, such as galaxies, will remain together, and they too will be subject to heat death as the universe expands and cools. Other explanations of dark energy, called phantom energy theories, suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn apart by the ever-increasing expansion in a so-called Big Rip.[158]

Religious and philosophical interpretations
Main article: Religious interpretations of the Big Bang theory
As a description of the origin of the universe, the Big Bang has significant bearing on religion and philosophy.[159][160] As a result, it has become one of the liveliest areas in the discourse between science and religion.[161] Some believe the Big Bang implies a creator,[162][163] while others argue that Big Bang cosmology makes the notion of a creator superfluous.[160][164]

See also
Anthropic principle – Hypothesis about sapient life and the universe
Big Bounce – Model for the origin of the universe
Big Crunch – Theoretical scenario for the ultimate fate of the universe
Cold Big Bang – Designation of an absolute zero temperature at the beginning of the Universe
Cosmic Calendar – Method to visualize the chronology of the universe
Cosmogony – Branch of science or a theory concerning the origin of the universe
Eureka: A Prose Poem – Lengthy non-fiction work by American author Edgar Allan Poe, a Big Bang speculation
Future of an expanding universe – Future scenario if the expansion of the universe will continue forever or not
Heat death of the universe – Possible fate of the universe. Also known as the Big Chill and the Big Freeze
Shape of the universe – The local and global geometry of the universe
Steady-state model – Model of the universe – alternative to the Big Bang model, a discredited theory that denied the Big Bang and posited that the universe always existed
Notes
 Further information of, and references for, tests of general relativity are given in the article tests of general relativity.
 There is no consensus about how long the Big Bang phase lasted. For some writers, this denotes only the initial singularity, for others the whole history of the universe. Usually, at least the first few minutes (during which helium is synthesized) are said to occur "during the Big Bang".
 It is commonly reported that Hoyle intended this to be pejorative. However, Hoyle later denied that, saying that it was just a striking image meant to emphasize the difference between the two theories for radio listeners.[47]
 Strictly, dark energy in the form of a cosmological constant drives the universe towards a flat state; however, our universe remained close to flat for several billion years before the dark energy density became significant.
References
 Bridge, Mark (Director) (30 July 2014). First Second of the Big Bang. How The Universe Works. Silver Spring, Maryland. Science Channel.
 Silk 2009, p. 208.
 Singh 2004, p. 560. Book limited to 532 pages. Correct source page requested.
 NASA/WMAP Science Team (6 June 2011). "Cosmology: The Study of the Universe". Universe 101: Big Bang Theory. Washington, D.C.: NASA. Archived from the original on 29 June 2011. Retrieved 18 December 2019. The second section discusses the classic tests of the Big Bang theory that make it so compelling as the most likely valid and accurate description of our universe.
 Chow 2008, p. 211
 Partridge 1995, p. xvii
 Kragh 1996, p. 319: "At the same time that observations tipped the balance definitely in favor of relativistic big-bang theory, ..."
 "Planck reveals an almost perfect universe". Max-Planck-Gesellschaft. 21 March 2013. Retrieved 17 November 2020.
 Peebles, P. J. E.; Ratra, Bharat (22 April 2003). "The cosmological constant and dark energy". Reviews of Modern Physics. 75 (2): 559–606. arXiv:astro-ph/0207347. Bibcode:2003RvMP...75..559P. doi:10.1103/RevModPhys.75.559. S2CID 118961123.
 Wright, Edward L. (24 May 2013). "Frequently Asked Questions in Cosmology: What is the evidence for the Big Bang?". Ned Wright's Cosmology Tutorial. Los Angeles: Division of Astronomy & Astrophysics, University of California, Los Angeles. Archived from the original on 20 June 2013. Retrieved 25 November 2019.
 Francis, Charles (2018). Light after Dark I: Structures of the Sky. Troubador Publishing Ltd. p. 199. ISBN 9781785897122.
 Ivanchik, Alexandre V.; Potekhin, Alexander Y.; Varshalovich, Dmitry A. (March 1999). "The fine-structure constant: a new observational limit on its cosmological variation and some theoretical consequences". Astronomy & Astrophysics. 343 (2): 439–445. arXiv:astro-ph/9810166. Bibcode:1999A&A...343..439I.
 Turyshev, Slava G. (November 2008). "Experimental Tests of General Relativity". Annual Review of Nuclear and Particle Science. 58 (1): 207–248. arXiv:0806.1731. Bibcode:2008ARNPS..58..207T. doi:10.1146/annurev.nucl.58.020807.111839. S2CID 119199160.
 Ishak, Mustapha (December 2019). "Testing general relativity in cosmology". Living Reviews in Relativity. 22 (1): 204. arXiv:1806.10122. Bibcode:2019LRR....22....1I. doi:10.1007/s41114-018-0017-4. PMC 6299071. PMID 30613193. 1.
 Goodman, Jeremy (15 August 1995). "Geocentrism reexamined" (PDF). Physical Review D. 52 (4): 1821–1827. arXiv:astro-ph/9506068. Bibcode:1995PhRvD..52.1821G. doi:10.1103/PhysRevD.52.1821. PMID 10019408. S2CID 37979862. Archived (PDF) from the original on 2 May 2019. Retrieved 2 December 2019.
 Kolb & Turner 1988, chpt. 3
 Enqvist, K.; Sirkka, J. (September 1993). "Chemical equilibrium in QCD gas in the early universe". Physics Letters B. 314 (3–4): 298–302. arXiv:hep-ph/9304273. Bibcode:1993PhLB..314..298E. doi:10.1016/0370-2693(93)91239-J. S2CID 119406262.
 Hawking & Ellis 1973
 Wall, Mike (21 October 2011). "The Big Bang: What Really Happened at Our Universe's Birth?". The History & Future of the Cosmos. Space.com. Retrieved 7 September 2023.
 Roos 2012, p. 216: "This singularity is termed the Big Bang."
 Drees 1990, pp. 223–224
 Planck Collaboration (October 2016). "Planck 2015 results. XIII. Cosmological parameters". Astronomy & Astrophysics. 594: Article A13. arXiv:1502.01589. Bibcode:2016A&A...594A..13P. doi:10.1051/0004-6361/201525830. S2CID 119262962. (See Table 4, Age/Gyr, last column.)
 Musser, George (22 September 2003). "Why didn't all this matter immediately collapse into a black hole?". Scientific American. Retrieved 22 March 2020.
 Unruh, W.G.; Semenoff, G.W., eds. (1988). The early universe. Reidel. ISBN 90-277-2619-1. OCLC 905464231.
 Hawley, John F.; Holcomb, Katherine A. (7 July 2005). Foundations of Modern Cosmology. OUP Oxford. p. 355. ISBN 9780198530961.
 "Brief History of the Universe". www.astro.ucla.edu. Retrieved 28 April 2020.
 Guth 1998
 "Big Bang models back to Planck time". hyperphysics.phy-astr.gsu.edu. Retrieved 28 April 2020.
 Schewe, Phillip F.; Stein, Ben P. (20 April 2005). "An Ocean of Quarks". Physics News Update. Vol. 728, no. 1. Archived from the original on 23 April 2005. Retrieved 30 November 2019.
 Høg, Erik (2014). "Astrosociology: Interviews about an infinite universe". Asian Journal of Physics. arXiv:1408.4795. Bibcode:2014arXiv1408.4795H.
 Kolb & Turner 1988, chpt. 6
 Kolb & Turner 1988, chpt. 7
 Weenink, Jan (26 February 2009). "Baryogenesis" (PDF). Tomislav Prokopec. Archived (PDF) from the original on 9 October 2022.
 Kolb & Turner 1988, chpt. 4
 Peacock 1999, chpt. 9
 Clavin, Whitney; Jenkins, Ann; Villard, Ray (7 January 2014). "NASA's Hubble and Spitzer Team up to Probe Faraway Galaxies". Jet Propulsion Laboratory. Washington, D.C.: NASA. Archived from the original on 3 September 2019. Retrieved 8 January 2014.
 Spergel, David N.; Verde, Licia; Peiris, Hiranya V.; et al. (September 2003). "First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters". The Astrophysical Journal Supplement Series. 148 (1): 175–194. arXiv:astro-ph/0302209. Bibcode:2003ApJS..148..175S. doi:10.1086/377226. S2CID 10794058.
 Jarosik, Norman; Bennett, Charles L.; Dunkley, Jo; et al. (February 2011). "Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic Results" (PDF). The Astrophysical Journal Supplement Series. 192 (2): Article 14. arXiv:1001.4744. Bibcode:2011ApJS..192...14J. doi:10.1088/0067-0049/192/2/14. hdl:2152/43001. S2CID 46171526. Archived (PDF) from the original on 14 September 2019. Retrieved 2 December 2019. (See Table 8.)
 Overbye, Dennis (15 April 2020). "Why The Big Bang Produced Something Rather Than Nothing – How did matter gain the edge over antimatter in the early universe? Maybe, just maybe, neutrinos". The New York Times. Archived from the original on 15 April 2020. Retrieved 16 April 2020.
 Manly 2011, chpt. 7: "The Ultimate Free Lunch"[page needed].
 "'Big bang' astronomer dies". Sci/Tech. BBC News. London: BBC. 22 August 2001. Archived from the original on 3 September 2019. Retrieved 2 December 2019.
 "Hoyle on the Radio: Creating the 'Big Bang'". Fred Hoyle: An Online Exhibition. Cambridge: St John's College. Archived from the original on 26 May 2014. Retrieved 2 December 2019.
 Kragh, Helge (April 2013). "Big Bang: the etymology of a name". Astronomy & Geophysics. 54 (2): 2.28–2.30. Bibcode:2013A&G....54b2.28K. doi:10.1093/astrogeo/att035.
 Mattson, Barbara (Project Leader) (8 December 2017). "Hoyle Scoffs at 'Big Bang' Universe Theory". Cosmic Times (hosted by Imagine the Universe!). Greenbelt, Maryland: NASA: High Energy Astrophysics Science Archive Research Center. OCLC 227004453. Archived from the original on 10 March 2018. Retrieved 2 December 2019.
 Mathew, Santhosh (2013). Essays on the Frontiers of Modern Astrophysics and Cosmology. Springer Science & Business Media. p. 13. ISBN 978-3-319-01887-4.
 Timothy Ferris writes: "The term "big bang" was coined with derisive intent by Fred Hoyle, and its endurance testifies to Sir Fred's creativity and wit. Indeed, the term survived an international competition in which three judges — the television science reporter Hugh Downs, the astronomer Carl Sagan, and myself — sifted through 13,099 entries from 41 countries and concluded that none was apt enough to replace it. No winner was declared, and like it or not, we are stuck with "big bang.""[54]
 Croswell 1995, p. 113, chapter 9
 Mitton 2011, p. 129: "To create a picture in the mind of the listener, Hoyle had likened the explosive theory of the universe's origin to a 'big bang'."
 Kragh, Helge (2014). Masters of the Universe: Conversations with Cosmologists of the Past. Oxford University Press. p. 210n30. ISBN 978-0-19-103442-8.
 Hoyle stated: "I was constantly striving over the radio – where I had no visual aids, nothing except the spoken word – for visual images. And that seemed to be one way of distinguishing between the steady-state and the explosive big bang. And so that was the language I used."[43][49]
 Kaler, James B. (2013). The Little Book of Stars. Springer Science & Business Media. p. 3. ISBN 978-0-387-21621-8.
 Emam, Moataz (2021). Covariant Physics: From Classical Mechanics to General Relativity and Beyond. Oxford University Press. pp. 208–246. ISBN 978-0-19-886489-9. The term "Big Bang" is an unfortunate misnomer. It implies an "explosion," and explosions are events that happen in space. This is incorrect; the term describes the first instant in the expansion of space itself. Some would even interpret it as the very beginning of the universe, evolving from "nothing." It is hard to imagine exactly what it was, but an explosion it most definitely wasn't.
 Moskowitz, Clara (2010). "Was the Big Bang Really an Explosion?". livescience.com.
Ferris, Timothy (1998). The Whole Shebang: A State of the Universe Report. Simon and Schuster. p. 323n10. ISBN 978-0-684-83861-8.
Gaither, Carl C.; Cavazos-Gaither, Alma E. (2012). Gaither's Dictionary of Scientific Quotations (2nd ed.). Springer Science & Business Media. ISBN 978-1-4614-1114-7. (quoting Ferris)
 Moskowitz, Clara (25 September 2012). "Hubble Telescope Reveals Farthest View Into Universe Ever". Space.com. New York: Future plc. Archived from the original on 12 October 2019. Retrieved 3 December 2019.
 Slipher, Vesto M. (1913). "The Radial Velocity of the Andromeda Nebula". Lowell Observatory Bulletin. 1 (8): 56–57. Bibcode:1913LowOB...2...56S.
 Slipher, Vesto M. (January 1915). "Spectrographic Observations of Nebulae". Popular Astronomy. 23: 21–24. Bibcode:1915PA.....23...21S.
 Friedman, Alexander (December 1922). "Über die Krümmung des Raumes". Zeitschrift für Physik (in German). 10 (1): 377–386. Bibcode:1922ZPhy...10..377F. doi:10.1007/BF01332580. S2CID 125190902.
Translated in: Friedmann, Alexander (December 1999). "On the Curvature of Space". General Relativity and Gravitation. 31 (12): 1991–2000. Bibcode:1999GReGr..31.1991F. doi:10.1023/A:1026751225741. S2CID 122950995.
 Hubble, Edwin (15 March 1929). "A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae". Proceedings of the National Academy of Sciences. 15 (3): 168–173. Bibcode:1929PNAS...15..168H. doi:10.1073/pnas.15.3.168. PMC 522427. PMID 16577160. Archived from the original on 1 October 2006. Retrieved 28 November 2019.
 Christianson 1995
 Lemaître, Georges (April 1927). "Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques". Annales de la Société scientifique de Bruxelles (in French). 47: 49–59. Bibcode:1927ASSB...47...49L.
Translated in: Lemaître, Georges (March 1931). "A Homogeneous Universe of Constant Mass and Increasing Radius accounting for the Radial Velocity of Extra-galactic Nebulæ". Monthly Notices of the Royal Astronomical Society. 91 (5): 483–490. Bibcode:1931MNRAS..91..483L. doi:10.1093/mnras/91.5.483.
 Lemaître, Abbé Georges (24 October 1931). "Contributions to a British Association Discussion on the Evolution of the Universe". Nature. 128 (3234): 704–706. Bibcode:1931Natur.128..704L. doi:10.1038/128704a0. S2CID 4028196.
 Kragh 1996
 "Big bang theory is introduced – 1927". A Science Odyssey. Boston, Massachusetts: WGBH Boston. 1998. Archived from the original on 23 April 1999. Retrieved 31 July 2014.
 Eddington, Arthur S. (21 March 1931). "The End of the World: from the Standpoint of Mathematical Physics". Nature. 127 (3203): 447–453. Bibcode:1931Natur.127..447E. doi:10.1038/127447a0. S2CID 4140648.
 Appolloni, Simon (17 June 2011). "'Repugnant', 'Not Repugnant at All': How the Respective Epistemic Attitudes of Georges Lemaitre and Sir Arthur Eddington Influenced How Each Approached the Idea of a Beginning of the Universe". IBSU Scientific Journal. 5 (1): 19–44.
 Lemaître, Georges (9 May 1931). "The Beginning of the World from the Point of View of Quantum Theory". Nature. 127 (3210): 706. Bibcode:1931Natur.127..706L. doi:10.1038/127706b0. ISSN 0028-0836. S2CID 4089233.
 Milne 1935
 Tolman 1934
 Zwicky, Fritz (15 October 1929). "On the Red Shift of Spectral Lines through Interstellar Space". Proceedings of the National Academy of Sciences. 15 (10): 773–779. Bibcode:1929PNAS...15..773Z. doi:10.1073/pnas.15.10.773. PMC 522555. PMID 16577237.
 Hoyle, Fred (October 1948). "A New Model for the Expanding Universe". Monthly Notices of the Royal Astronomical Society. 108 (5): 372–382. Bibcode:1948MNRAS.108..372H. doi:10.1093/mnras/108.5.372.
 Alpher, Ralph A.; Bethe, Hans; Gamow, George (1 April 1948). "The Origin of Chemical Elements". Physical Review. 73 (7): 803–804. Bibcode:1948PhRv...73..803A. doi:10.1103/PhysRev.73.803. PMID 18877094.
 Alpher, Ralph A.; Herman, Robert (13 November 1948). "Evolution of the Universe". Nature. 162 (4124): 774–775. Bibcode:1948Natur.162..774A. doi:10.1038/162774b0. S2CID 4113488.
 Penzias, Arno A.; Wilson, R. W. (July 1965). "A Measurement of Excess Antenna Temperature at 4080 Mc/s". The Astrophysical Journal. 142: 419–421. Bibcode:1965ApJ...142..419P. doi:10.1086/148307. Archived from the original on 14 October 2019. Retrieved 5 December 2019.
 Hawking, Stephen W.; Ellis, George F. R. (April 1968). "The Cosmic Black-Body Radiation and the Existence of Singularities in our Universe". The Astrophysical Journal. 152: 25. Bibcode:1968ApJ...152...25H. doi:10.1086/149520.
 Hawking, Stephen W.; Penrose, Roger (27 January 1970). "The Singularities of Gravitational Collapse and Cosmology". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 314 (1519): 529–548. Bibcode:1970RSPSA.314..529H. doi:10.1098/rspa.1970.0021.
 Guth, Alan (15 January 1981). "Inflationary universe: A possible solution to the horizon and flatness problems". Physical Review D. 23 (2): 347–356. Bibcode:1981PhRvD..23..347G. doi:10.1103/PhysRevD.23.347.
 Huchra, John P. (2008). "The Hubble Constant". Science. 256 (5055): 321–5. doi:10.1126/science.256.5055.321. PMID 17743107. S2CID 206574821. Archived from the original on 30 September 2019. Retrieved 5 December 2019.
 Livio 2000, p. 160
 Navabi, Ali Akbar; Riazi, Nematollah (March 2003). "Is the Age Problem Resolved?". Journal of Astrophysics and Astronomy. 24 (1–2): 3–10. Bibcode:2003JApA...24....3N. doi:10.1007/BF03012187. S2CID 123471347.
 Boggess, Nancy W.; Mather, John C.; Weiss, Rainer; et al. (1 October 1992). "The COBE Mission: Its Design and Performance Two Years after the launch". The Astrophysical Journal. 397: 420–429. Bibcode:1992ApJ...397..420B. doi:10.1086/171797.
 Spergel, David N.; Bean, Rachel; Doré, Olivier; et al. (June 2007). "Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology". The Astrophysical Journal Supplement Series. 170 (2): 377–408. arXiv:astro-ph/0603449. Bibcode:2007ApJS..170..377S. doi:10.1086/513700. S2CID 1386346.
 Reiss, Adam G.; Filippenko, Alexei V.; Challis, Peter; Clocchiatti, Alejandro; Diercks, Alan; Garnavich, Peter M.; Gilliland, Ron L.; Hogan, Craig J.; Jha, Saurabh; Kirshner, Robert P.; Leibundgut, B.; Phillips, M. M.; Reiss, David; Schmidt, Brian P.; Schommer, Robert A.; Smith, R. Chris; Spyromilio, J.; Stubbs, Christopher; Suntzeff, Nicholas B.; Tonry, John (1998). "Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant". The Astronomical Journal. 116 (3): 1009–1038. arXiv:astro-ph/9805201. Bibcode:1998AJ....116.1009R. doi:10.1086/300499. S2CID 15640044.
 Perlmutter, S.; Aldering, G.; Goldhaber, G.; Knop, R.A.; Nugent, P.; Castro, P.G.; Deustua, S.; Fabbro, S.; Goobar, A.; Groom, D.E.; Hook, I.M.; Kim, A.G.; Kim, M.Y.; Lee, J.C.; Nunes, N.J.; Pain, R.; Pennypacker, C.R.; Quimby, R.; Lidman, C.; Ellis, R.S.; Irwin, M.; McMahon, R.G.; Ruiz-Lapuente, P.; Walton, N.; Schaefer, B.; Boyle, B.J.; Filippenko, A.V.; Matheson, T.; Fruchter, A.S.; Panagia, N.; Newberg, H.J.M.; Couch, W.J. (1999). "Measurements of Omega and Lambda from 42 High-Redshift Supernovae". The Astrophysical Journal. 517 (2): 565–586. arXiv:astro-ph/9812133. Bibcode:1999ApJ...517..565P. doi:10.1086/307221. S2CID 118910636.
 Krauss 2012, p. 118
 Gladders, Michael D.; Yee, H. K. C.; Majumdar, Subhabrata; et al. (20 January 2007). "Cosmological Constraints from the Red-Sequence Cluster Survey". The Astrophysical Journal. 655 (1): 128–134. arXiv:astro-ph/0603588. Bibcode:2007ApJ...655..128G. doi:10.1086/509909. S2CID 10855653.
 Shellard, Paul; et al., eds. (2012). "The Four Pillars of the Standard Cosmology". Outreach. Cambridge, UK: Centre for Theoretical Cosmology; University of Cambridge. Archived from the original on 2 November 2013. Retrieved 6 December 2019.
From retired website: Shellard, Paul; et al., eds. (2006). "The Four Pillars of the Standard Cosmology". Cambridge Relativity and Cosmology. Cambridge, UK: University of Cambridge. Archived from the original on 28 January 1998. Retrieved 6 December 2019.
 Sadoulet, Bernard; et al. "Direct Searches for Dark Matter" (PDF). Astro2010: The Astronomy and Astrophysics Decadal Survey (white paper). Washington, D.C.: National Academies Press on behalf of the National Research Council of the National Academy of Sciences. OCLC 850950122. Archived from the original on 13 April 2009. Retrieved 8 December 2019.
 Diemand, Jürg; Zemp, Marcel; Moore, Ben; Stadel, Joachim; Carollo, C. Marcella (December 2005). "Cusps in cold dark matter haloes". Monthly Notices of the Royal Astronomical Society. 364 (2): 665–673. arXiv:astro-ph/0504215. Bibcode:2005MNRAS.364..665D. doi:10.1111/j.1365-2966.2005.09601.x. S2CID 117769706.
 Bullock, James S. (2010). "Notes on the Missing Satellites Problem". In Martinez-Delgado, David; Mediavilla, Evencio (eds.). Local Group Cosmology. pp. 95–122. arXiv:1009.4505. doi:10.1017/CBO9781139152303.004. ISBN 9781139152303. S2CID 119270708.
 Cahn, Robert N.; et al. (2009). "Whitepaper: For a Comprehensive Space-Based Dark Energy Mission" (PDF). Astro2010: The Astronomy and Astrophysics Decadal Survey, Science White Papers, no. 35 (white paper). Washington, D.C.: National Academies Press on behalf of the National Research Council of the National Academy of Sciences. 2010: 35. Bibcode:2009astro2010S..35B. OCLC 850950122. Archived from the original on 7 August 2011. Retrieved 8 December 2019.
 Bunn, E. F.; Hogg, D. W. (2009). "The kinematic origin of the cosmological redshift". American Journal of Physics. 77 (8): 688–694. arXiv:0808.1081. Bibcode:2009AmJPh..77..688B. doi:10.1119/1.3129103. S2CID 1365918.
 Di Valentino, Eleonora; Mena, Olga; Pan, Supriya; Visinelli, Luca; Yang, Weiqiang; Melchiorri, Alessandro; Mota, David F.; Riess, Adam G.; Silk, Joseph (2021). "In the realm of the Hubble tension—a review of solutions". Classical and Quantum Gravity. 38 (15): 153001. arXiv:2103.01183. Bibcode:2021CQGra..38o3001D. doi:10.1088/1361-6382/ac086d. S2CID 232092525.
 White, Martin (1999). "Anisotropies in the CMB" (PDF). In Arisaka, Katsushi; Bern, Zvi (eds.). DPF 99: Proceedings of the Los Angeles Meeting. Division of Particles and Fields Conference 1999 (DPF '99). Los Angeles: University of California, Los Angeles on behalf of the American Physical Society. arXiv:astro-ph/9903232. Bibcode:1999dpf..conf.....W. OCLC 43669022. Talk #9-10: The Cosmic Microwave Background. Archived (PDF) from the original on 4 February 2017. Retrieved 9 December 2019.
 Bennett, Charles L.; Larson, Davin; Weiland, Janet L.; et al. (October 2013). "Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results". The Astrophysical Journal Supplement Series. 208 (2): Article 20. arXiv:1212.5225. Bibcode:2013ApJS..208...20B. doi:10.1088/0067-0049/208/2/20. S2CID 119271232.
 Gannon, Megan (21 December 2012). "New 'Baby Picture' of Universe Unveiled". Space.com. New York: Future plc. Archived from the original on 29 October 2019. Retrieved 9 December 2019.
 Wright 2004, p. 291
 Melchiorri, Alessandro; Ade, Peter A.R.; de Bernardis, Paolo; et al. (20 June 2000). "A Measurement of Ω from the North American Test Flight of Boomerang". The Astrophysical Journal Letters. 536 (2): L63–L66. arXiv:astro-ph/9911445. Bibcode:2000ApJ...536L..63M. doi:10.1086/312744. PMID 10859119. S2CID 27518923.
 de Bernardis, Paolo; Ade, Peter A.R.; Bock, James J.; et al. (27 April 2000). "A Flat Universe from High-Resolution Maps of the Cosmic Microwave Background Radiation" (PDF). Nature. 404 (6781): 955–959. arXiv:astro-ph/0004404. Bibcode:2000Natur.404..955D. doi:10.1038/35010035. hdl:10044/1/60851. PMID 10801117. S2CID 4412370. Archived (PDF) from the original on 2 May 2019. Retrieved 10 December 2019.
 Miller, Andre D.; Caldwell, Robert H.; Devlin, Mark Joseph; et al. (10 October 1999). "A Measurement of the Angular Power Spectrum of the Cosmic Microwave Background from l = 100 to 400". The Astrophysical Journal Letters. 524 (1): L1–L4. arXiv:astro-ph/9906421. Bibcode:1999ApJ...524L...1M. doi:10.1086/312293. S2CID 1924091.
 Steigman, Gary (February 2006). "Primordial Nucleosynthesis: Successes And Challenges". International Journal of Modern Physics E. 15 (1): 1–36. arXiv:astro-ph/0511534. Bibcode:2006IJMPE..15....1S. CiteSeerX 10.1.1.337.542. doi:10.1142/S0218301306004028. S2CID 12188807.
 Ryden 2003
 O'Callaghan, Jonathan (6 December 2022). "Astronomers Grapple with JWST's Discovery of Early Galaxies". Scientific American. Retrieved 13 February 2023.
 Bertschinger, Edmund (2000). "Cosmological Perturbation Theory and Structure Formation". arXiv:astro-ph/0101009.
 Bertschinger, Edmund (September 1998). "Simulations of Structure Formation in the Universe" (PDF). Annual Review of Astronomy and Astrophysics. 36 (1): 599–654. Bibcode:1998ARA&A..36..599B. doi:10.1146/annurev.astro.36.1.599. S2CID 29015610. Archived from the original (PDF) on 9 March 2019.
 "BICEP2 March 2014 Results and Data Products". The BICEP and Keck Array CMB Experiments. Cambridge, Massachusetts: FAS Research Computing, Harvard University. 16 December 2014 [Results originally released on 17 March 2014]. Archived from the original on 18 March 2014. Retrieved 10 December 2019.
 Clavin, Whitney (17 March 2014). "NASA Technology Views Birth of the Universe". Jet Propulsion Laboratory. Washington, D.C.: NASA. Archived from the original on 10 October 2019. Retrieved 10 December 2019.
 Overbye, Dennis (17 March 2014). "Space Ripples Reveal Big Bang's Smoking Gun". Space & Cosmos. The New York Times. New York. ISSN 0362-4331. Archived from the original on 17 March 2014. Retrieved 11 December 2019. "A version of this article appears in print on March 18, 2014, Section A, Page 1 of the New York edition with the headline: Space Ripples Reveal Big Bang's Smoking Gun." The online version of this article was originally titled "Detection of Waves in Space Buttresses Landmark Theory of Big Bang".
 Overbye, Dennis (24 March 2014). "Ripples From the Big Bang". Out There. The New York Times. New York. ISSN 0362-4331. Archived from the original on 25 March 2014. Retrieved 24 March 2014. "A version of this article appears in print on March 25, 2014, Section D, Page 1 of the New York edition with the headline: Ripples From the Big Bang."
 Fumagalli, Michele; O'Meara, John M.; Prochaska, J. Xavier (2 December 2011). "Detection of Pristine Gas Two Billion Years After the Big Bang". Science. 334 (6060): 1245–1249. arXiv:1111.2334. Bibcode:2011Sci...334.1245F. doi:10.1126/science.1213581. PMID 22075722. S2CID 2434386.
 Stephens, Tim (10 November 2011). "Astronomers find clouds of primordial gas from the early universe". Uc Santa Cruz News. Santa Cruz, CA: University of California, Santa Cruz. Archived from the original on 14 November 2011. Retrieved 11 December 2019.
 Perley, Daniel (21 February 2005). "Determination of the Universe's Age, to". Berkeley, California: Department of Astronomy, University of California, Berkeley. Archived from the original on 11 September 2006. Retrieved 11 December 2019.
 Yang, R. J., & Zhang, S. N. (2010). The age problem in the ΛCDM model. Monthly Notices of the Royal Astronomical Society, 407(3), pp. 1835–1841.
 Yu, H., & Wang, F. Y. (2014). Reconciling the cosmic age problem in the $$ R_\mathrm {h}= ct $$ universe. The European Physical Journal C, 74(10), 3090.
 Srianand, Raghunathan; Noterdaeme, Pasquier; Ledoux, Cédric; et al. (May 2008). "First detection of CO in a high-redshift damped Lyman-α system". Astronomy & Astrophysics. 482 (3): L39–L42. arXiv:0804.0116. Bibcode:2008A&A...482L..39S. doi:10.1051/0004-6361:200809727.
 Avgoustidis, Anastasios; Luzzi, Gemma; Martins, Carlos J.A.P.; et al. (14 February 2012). "Constraints on the CMB temperature-redshift dependence from SZ and distance measurements". Journal of Cosmology and Astroparticle Physics. 2012 (2): Article 013. arXiv:1112.1862. Bibcode:2012JCAP...02..013A. CiteSeerX 10.1.1.758.6956. doi:10.1088/1475-7516/2012/02/013. S2CID 119261969.
 Belušević 2008, p. 16
 Ghosh, Pallab (11 February 2016). "Einstein's gravitational waves 'seen' from black holes". Science & Environment. BBC News. London: BBC. Archived from the original on 11 February 2016. Retrieved 13 April 2017.
 Billings, Lee (12 February 2016). "The Future of Gravitational Wave Astronomy". Scientific American. Archived from the original on 13 February 2016. Retrieved 13 April 2017.
 Earman, John; Mosterín, Jesús (March 1999). "A Critical Look at Inflationary Cosmology". Philosophy of Science. 66 (1): 1–49. doi:10.1086/392675. JSTOR 188736. S2CID 120393154.
 Hawking & Israel 2010, pp. 581–638, chpt. 12: "Singularities and time-asymmetry" by Roger Penrose.
 Penrose 1989
 Steinhardt, Paul J. (April 2011). "The Inflation Debate: Is the theory at the heart of modern cosmology deeply flawed?" (PDF). Scientific American. Vol. 304, no. 4. pp. 36–43. doi:10.1038/scientificamerican0411-36. Archived (PDF) from the original on 1 November 2019. Retrieved 23 December 2019.
 Sakharov, Andrei D. (10 January 1967). "Нарушение СР-инвариантности, С-асимметрия и барионная асимметрия Вселенной" [Violation of CP-invariance, C-asymmetry and baryon asymmetry of the Universe] (PDF). Pis'ma v ZhETF (in Russian). 5 (1): 32–35. Archived (PDF) from the original on 28 July 2018.
Translated in: Sakharov, Andrei D. (10 January 1967). "Violation of CP Invariance, С Asymmetry, and Baryon Asymmetry of the Universe" (PDF). JETP Letters. 5 (1): 24–27. Archived (PDF) from the original on 9 November 2019. Retrieved 13 December 2019.
Reprinted in: Kolb & Turner 1988, pp. 371–373
 Weinberg, Nevin N.; Kamionkowski, Marc (May 2003). "Constraining dark energy from the abundance of weak gravitational lenses". Monthly Notices of the Royal Astronomical Society. 341 (1): 251–262. arXiv:astro-ph/0210134. Bibcode:2003MNRAS.341..251W. doi:10.1046/j.1365-8711.2003.06421.x. S2CID 1193946.
 Tanabashi, M. 2018, pp. 406–413, chpt. 27: "Dark Energy" (Revised September 2017) by David H. Weinberg and Martin White.
Olive 2014, pp. 361–368, chpt. 26: "Dark Energy" (November 2013) by Michael J. Mortonson, David H. Weinberg, and Martin White. Bibcode:2014arXiv1401.0046M
 Rugh, Svend E.; Zinkernagel, Henrik (December 2002). "The quantum vacuum and the cosmological constant problem". Studies in History and Philosophy of Science Part B. 33 (4): 663–705. arXiv:hep-th/0012253. Bibcode:2002SHPMP..33..663R. doi:10.1016/S1355-2198(02)00033-3. S2CID 9007190.
 Keel, William C. (October 2009) [Last changes: February 2015]. "Dark Matter". Bill Keel's Lecture Notes – Galaxies and the Universe. Archived from the original on 3 May 2019. Retrieved 15 December 2019.
 Tanabashi, M. 2018, pp. 396–405, chpt. 26: "Dark Matter" (Revised September 2017) by Manuel Drees and Gilles Gerbier.
Yao, W.-M. 2006, pp. 233–237, chpt. 22: "Dark Matter" (September 2003) by Manuel Drees and Gilles Gerbier.
 Dodelson, Scott (31 December 2011). "The Real Problem with MOND". International Journal of Modern Physics D. 20 (14): 2749–2753. arXiv:1112.1320. Bibcode:2011IJMPD..20.2749D. doi:10.1142/S0218271811020561. S2CID 119194106.
 Kolb & Turner 1988, chpt. 8
 Penrose 2007
 Filippenko, Alexei V.; Pasachoff, Jay M. (March–April 2002). "A Universe from Nothing". Mercury. Vol. 31, no. 2. p. 15. Bibcode:2002Mercu..31b..15F. Archived from the original on 22 October 2013. Retrieved 10 March 2010.
 Lawrence M. Krauss (Speaker); R. Elisabeth Cornwell (Producer) (21 October 2009). 'A Universe From Nothing' by Lawrence Krauss, AAI 2009 (Video). Washington, D.C.: Richard Dawkins Foundation for Reason and Science. Archived from the original on 23 November 2021. Retrieved 17 October 2011.
 Hawking & Israel 2010, pp. 504–517, chpt. 9: "The big bang cosmology — enigmas and nostrums" by Robert H. Dicke and Phillip J.E. Peebles.
 "Brief Answers to Cosmic Questions". Universe Forum. Cambridge, Massachusetts: Harvard–Smithsonian Center for Astrophysics. Archived from the original on 13 April 2016. Retrieved 18 December 2019. Archival site: "The Universe Forum's role as part of NASA's Education Support Network concluded in September, 2009."
 Davis, Tamara M.; Lineweaver, Charles H. (31 March 2004). "Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe". Publications of the Astronomical Society of Australia. 21 (1): 97–109. arXiv:astro-ph/0310808. Bibcode:2004PASA...21...97D. doi:10.1071/as03040. S2CID 13068122.
 Peacock, J. A. (2008). "A diatribe on expanding space". arXiv:0809.4573 [astro-ph].
 Starobinsky, Alexei (2000). "Future and Origin of Our Universe: Modern View". In Burdyuzha, V.; Khozin, G. (eds.). The Future of the Universe and the Future of Our Civilization. Singapore: World Scientific Publishing. p. 71. Bibcode:2000fufc.conf...71S. doi:10.1142/9789812793324_0008. ISBN 9810242646. S2CID 37813302. {{cite book}}: |work= ignored (help)
 Hawking 1988, p. 69.
 Carroll n.d.
 Beckers, Mike (16 February 2015). "Quantentrick schafft Urknall-Singularität ab" [Quantum Trick Eliminates the Big Bang Singularity]. Cosmology. Spektrum der Wissenschaft (in German). Archived from the original on 21 July 2017. Retrieved 19 December 2019. Google translation
Ali, Ahmed Farag; Das, Saurya (4 February 2015). "Cosmology from quantum potential". Physics Letters B. 741: 276–279. arXiv:1404.3093v3. Bibcode:2015PhLB..741..276F. doi:10.1016/j.physletb.2014.12.057. S2CID 55463396.
Lashin, Elsayed I. (7 March 2016). "On the correctness of cosmology from quantum potential". Modern Physics Letters A. 31 (7): 1650044. arXiv:1505.03070. Bibcode:2016MPLA...3150044L. doi:10.1142/S0217732316500449. S2CID 119220266.
Das, Saurya; Rajat K., Bhaduri (21 May 2015). "Dark matter and dark energy from a Bose–Einstein condensate". Classical and Quantum Gravity. 32 (10): 105003. arXiv:1411.0753. Bibcode:2015CQGra..32j5003D. doi:10.1088/0264-9381/32/10/105003. S2CID 119247745.
 Hawking, Stephen W. (1996). "The Beginning of Time". Stephen Hawking (Lecture). London: The Stephen Hawking Foundation. Archived from the original on 6 November 2019. Retrieved 26 April 2017.
 Wall, Mike (24 June 2012). "The Big Bang Didn't Need God to Start Universe, Researchers Say". Space.com.
 Overbye, Dennis (22 May 2001). "Before the Big Bang, There Was . . . What?". The New York Times. Archived from the original on 27 February 2013.
 He, Dongshan; Gao, Dongfeng; Cai, Qing-yu (3 April 2014). "Spontaneous creation of the universe from nothing". Physical Review D. 89 (8): 083510. arXiv:1404.1207. Bibcode:2014PhRvD..89h3510H. doi:10.1103/PhysRevD.89.083510. S2CID 118371273.
 Lincoln, Maya; Wasser, Avi (1 December 2013). "Spontaneous creation of the Universe Ex Nihilo". Physics of the Dark Universe. 2 (4): 195–199. Bibcode:2013PDU.....2..195L. doi:10.1016/j.dark.2013.11.004. ISSN 2212-6864.
 Hartle, James H.; Hawking, Stephen W. (15 December 1983). "Wave function of the Universe". Physical Review D. 28 (12): 2960–2975. Bibcode:1983PhRvD..28.2960H. doi:10.1103/PhysRevD.28.2960. S2CID 121947045.
 Hawking 1988, p. 71.
 Langlois, David (2003). "Brane Cosmology". Progress of Theoretical Physics Supplement. 148: 181–212. arXiv:hep-th/0209261. Bibcode:2002PThPS.148..181L. doi:10.1143/PTPS.148.181. S2CID 9751130.
 Gibbons, Shellard & Rankin 2003, pp. 801–838, chpt. 43: "Inflationary theory versus the ekpyrotic/cyclic scenario" by Andrei Linde. Bibcode:2003ftpc.book..801L
 Than, Ker (8 May 2006). "Recycled Universe: Theory Could Solve Cosmic Mystery". Space.com. New York: Future plc. Archived from the original on 6 September 2019. Retrieved 19 December 2019.
 Kennedy, Barbara K. (1 July 2007). "What Happened Before the Big Bang?". News and Events. University Park, PA: Eberly College of Science, Pennsylvania State University. Archived from the original on 15 December 2019. Retrieved 19 December 2019.
Bojowald, Martin (August 2007). "What happened before the Big Bang?". Nature Physics. 3 (8): 523–525. Bibcode:2007NatPh...3..523B. doi:10.1038/nphys654.
 Linde, Andrei D. (May 1986). "Eternal Chaotic Inflation". Modern Physics Letters A. 1 (2): 81–85. Bibcode:1986MPLA....1...81L. doi:10.1142/S0217732386000129. S2CID 123472763. Archived from the original on 17 April 2019.
 Linde, Andrei D. (14 August 1986). "Eternally Existing Self-Reproducing Chaotic Inflationary Universe". Physics Letters B. 175 (4): 395–400. Bibcode:1986PhLB..175..395L. doi:10.1016/0370-2693(86)90611-8.
 NASA/WMAP Science Team (29 June 2015). "What is the Ultimate Fate of the Universe?". Universe 101: Big Bang Theory. Washington, D.C: NASA. Archived from the original on 15 October 2019. Retrieved 18 December 2019.
 Adams, Fred C.; Laughlin, Gregory (April 1997). "A dying universe: the long-term fate and evolution of astrophysical objects". Reviews of Modern Physics. 69 (2): 337–372. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/RevModPhys.69.337. S2CID 12173790..
 Caldwell, Robert R.; Kamionkowski, Marc; Weinberg, Nevin N. (15 August 2003). "Phantom Energy: Dark Energy with w<−1 Causes a Cosmic Doomsday". Physical Review Letters. 91 (7): 071301. arXiv:astro-ph/0302506. Bibcode:2003PhRvL..91g1301C. doi:10.1103/PhysRevLett.91.071301. PMID 12935004. S2CID 119498512.
 Harris 2002, p. 128
 Frame 2009, pp. 137–141
 Harrison 2010, p. 9
 Harris 2002, p. 129
 Craig, William Lane (December 1999). "The Ultimate Question of Origins: God and the Beginning of the Universe". Astrophysics and Space Science (Lecture). 269–270 (1–4): 721–738. Bibcode:1999Ap&SS.269..721C. doi:10.1023/A:1017083700096. S2CID 117794135.
Block et al. 2000, pp. 723–740 doi:10.1007/978-94-011-4114-7_85
Craig, William Lane. "The Ultimate Question of Origins: God and the Beginning of the Universe". Scholarly Writings: The Existence of God. Reasonable Faith. Dallas, TX. Archived from the original on 29 December 2019. Retrieved 21 December 2019.
 Hawking 1988, Introduction: "... a universe with no edge in space, no beginning or end in time, and nothing for a Creator to do." — Carl Sagan.
Bibliography
Belušević, Radoje (2008). Relativity, Astrophysics and Cosmology. Vol. 1. Weinheim: Wiley-VCH. ISBN 978-3-527-40764-4. OCLC 876678499.
Block, David L.; Puerari, Ivânio; Stockton, Alan; et al., eds. (2000). Toward a New Millennium in Galaxy Morphology: Proceedings of an International Conference 'Toward a New Millennium in Galaxy Morphology: from z=0 to the Lyman Break, held at the Eskom Conference Centre, Midrand, South Africa, September 13–18, 1999. Dordrecht: Kluwer Academic Publishers. doi:10.1007/978-94-011-4114-7. ISBN 978-94-010-5801-8. LCCN 00042415. OCLC 851369444. "Reprinted from Astrophysics and Space Science Volumes 269–270, Nos. 1–4, 1999".
Block, David L. (2012). "Georges Lemaître and Stigler's Law of Eponymy". In Holder, Rodney D.; Mitton, Simon (eds.). Georges Lemaître: Life, Science and Legacy. Astrophysics and Space Science Library. Vol. 395. Heidelberg; New York: Springer. pp. 89–96. arXiv:1106.3928v2. Bibcode:2012ASSL..395...89B. doi:10.1007/978-3-642-32254-9_8. ISBN 978-3-642-32253-2. LCCN 2012956159. OCLC 839779611. S2CID 119205665.
Carroll, Sean M. (n.d.). "Why Is There Something, Rather Than Nothing?". In Knox, Eleanor; Wilson, Alastair (eds.). Routledge Companion to the Philosophy of Physics. London: Routledge. arXiv:1802.02231v2. Bibcode:2018arXiv180202231C.
Chow, Tai L. (2008). Gravity, Black Holes, and the Very Early Universe: An Introduction to General Relativity and Cosmology. New York: Springer. ISBN 978-0-387-73629-7. LCCN 2007936678. OCLC 798281050.
Christianson, Gale E. (1995). Edwin Hubble: Mariner of the Nebulae. New York: Farrar, Straus and Giroux. ISBN 978-0-374-14660-3. LCCN 94045995. OCLC 461940674.
Croswell, Ken (1995). Alchemy of the Heavens: Searching for Meaning in the Milky Way. Illustrations by Philippe Van (1st Anchor Books ed.). New York: Anchor Books. ISBN 978-0-385-47213-5. LCCN 94030452. OCLC 1100389944.
d'Inverno, Ray (1992). Introducing Einstein's Relativity. Oxford, UK; New York: Clarendon Press; Oxford University Press. ISBN 978-0-19-859686-8. LCCN 91024894. OCLC 554124256.
Drees, William B. (1990). Beyond the Big Bang: Quantum Cosmologies and God. La Salle, IL: Open Court Publishing Company. ISBN 978-0-8126-9118-4. LCCN 90038498. OCLC 1088758264.
Farrell, John (2005). The Day Without Yesterday: Lemaître, Einstein, and the Birth of Modern Cosmology. New York: Thunder's Mouth Press. ISBN 978-1-56025-660-1. LCCN 2006272995. OCLC 61672162.
Frame, Tom (2009). Losing My Religion: Unbelief in Australia. Sydney: UNSW Press. ISBN 978-1-921410-19-2. OCLC 782015652.
Gibbons, Gary W.; Shellard, E.P.S.; Rankin, Stuart John, eds. (2003). The Future of Theoretical Physics and Cosmology: Celebrating Stephen Hawking's 60th Birthday. Cambridge, UK; New York: Cambridge University Press. ISBN 978-0-521-82081-3. LCCN 2002041704. OCLC 1088190774.
Guth, Alan H. (1998) [Originally published 1997]. The Inflationary Universe: Quest for a New Theory of Cosmic Origins. Foreword by Alan Lightman. London: Vintage Books. ISBN 978-0-09-995950-2. LCCN 96046117. OCLC 919672203.
Harris, James F. (2002). Analytic Philosophy of Religion. Handbook of Contemporary Philosophy of Religion. Vol. 3. Dordrecht: Kluwer Academic Publishers. ISBN 978-1-4020-0530-5. LCCN 2002071095. OCLC 237734029.
Harrison, Peter, ed. (2010). The Cambridge Companion to Science and Religion. Cambridge Companions to Religion. Cambridge, UK; New York: Cambridge University Press. ISBN 978-0-521-71251-4. LCCN 2010016793. OCLC 972341489.
Hawking, Stephen W.; Ellis, George F. R. (1973). The Large-Scale Structure of Space-Time. Cambridge, UK: Cambridge University Press. ISBN 978-0-521-20016-5. LCCN 72093671. OCLC 1120809270.
Hawking, Stephen W. (1988). A Brief History of Time: From the Big Bang to Black Holes. Introduction by Carl Sagan; illustrations by Ron Miller. New York: Bantam Dell Publishing Group. ISBN 978-0-553-10953-5. LCCN 87033333. OCLC 39256652.
Hawking, Stephen W.; Israel, Werner, eds. (2010) [Originally published 1979]. General Relativity: An Einstein Centenary Survey. Cambridge, UK: Cambridge University Press. ISBN 978-0-521-13798-0. LCCN 78062112. OCLC 759923541.
Kolb, Edward; Turner, Michael, eds. (1988). The Early Universe. Frontiers in Physics. Vol. 70. Redwood City, CA: Addison-Wesley. ISBN 978-0-201-11604-5. LCCN 87037440. OCLC 488800074.
Kragh, Helge (1996). Cosmology and Controversy: The Historical Development of Two Theories of the Universe. Princeton, NJ: Princeton University Press. ISBN 978-0-691-02623-7. LCCN 96005612. OCLC 906709898.
Krauss, Lawrence M. (2012). A Universe From Nothing: Why there is Something Rather than Nothing. Afterword by Richard Dawkins (1st Free Press hardcover ed.). New York: Free Press. ISBN 978-1-4516-2445-8. LCCN 2011032519. OCLC 709673181.
Livio, Mario (2000). The Accelerating Universe: Infinite Expansion, the Cosmological Constant, and the Beauty of the Cosmos (Audio book performance by Tom Parks, Brilliance Audio). Foreword by Allan Sandage. New York: John Wiley & Sons. ISBN 978-0-471-32969-5. LCCN 99022278. OCLC 226086793.
Manly, Steven L. (2011). Brandon, Jodi (ed.). Visions of the Multiverse. Pompton Plains, NJ: New Page Books. ISBN 978-1-60163-720-8. LCCN 2010052741. OCLC 609531953.
Martínez-Delgado, David, ed. (2013). Local Group Cosmology. Cambridge, UK: Cambridge University Press. ISBN 978-1-107-02380-2. LCCN 2013012345. OCLC 875920635. "Lectures presented at the XX Canary Islands Winter School of Astrophysics, held in Tenerife, Spain, November 17–18, 2008."
Milne, Edward Arthur (1935). Relativity, Gravitation and World-Structure. The International Series of Monographs on Physics. Oxford, UK; London: Clarendon Press; Oxford University Press. LCCN 35019093. OCLC 1319934.
Mitton, Simon (2011). Fred Hoyle: A Life in Science. Cambridge, UK; New York: Cambridge University Press. ISBN 978-0-521-18947-7. LCCN 2011293530. OCLC 774201415.
Olive, K.A.; et al. (Particle Data Group) (2014). "Review of Particle Physics" (PDF). Chinese Physics C. 38 (9): 1–708. arXiv:1412.1408. Bibcode:2014ChPhC..38i0001O. doi:10.1088/1674-1137/38/9/090001. PMID 10020536. S2CID 118395784. Archived (PDF) from the original on 30 January 2017. Retrieved 13 December 2019.
Partridge, R. Bruce (1995). 3K: The Cosmic Microwave Background Radiation. Cambridge Astrophysics Series. Vol. 25 (Illustrated ed.). Cambridge, UK: Cambridge University Press. ISBN 978-0-521-35808-8. LCCN 94014980. OCLC 1123849709.
Peacock, John A. (1999). Cosmological Physics. Cambridge Astrophysics Series. Cambridge, UK; New York: Cambridge University Press. ISBN 978-0-521-42270-3. LCCN 98029460. OCLC 60157380.
Penrose, Roger (1989). "Difficulties with Inflationary Cosmology". In Fenyves, Ervin J. (ed.). Fourteenth Texas Symposium on Relativistic Astrophysics. Annals of the New York Academy of Sciences. Vol. 571. New York: New York Academy of Sciences. pp. 249–264. Bibcode:1989NYASA.571..249P. doi:10.1111/j.1749-6632.1989.tb50513.x. ISBN 978-0-89766-526-1. ISSN 0077-8923. LCCN 89014030. OCLC 318253659. S2CID 122383812. "Symposium held in Dallas, Tex., Dec. 11-16, 1988."
Penrose, Roger (2007) [Originally published: London: Jonathan Cape, 2004]. The Road to Reality (1st Vintage Books ed.). New York: Vintage Books. ISBN 978-0-679-77631-4. LCCN 2008274126. OCLC 920157277. The 2004 edition of the book is available from the Internet Archive. Retrieved 20 December 2019.
Roos, Matts (2012) [Chapter originally published 2008]. "Expansion of the Universe – Standard Big Bang Model". In Engvold, Oddbjørn; Stabell, Rolf; Czerny, Bozena; Lattanzio, John (eds.). Astronomy and Astrophysics. Encyclopedia of Life Support Systems. Vol. II. Ramsey, Isle of Man: UNESCO in partnership with Eolss Publishers Co. Ltd. arXiv:0802.2005. Bibcode:2008arXiv0802.2005R. ISBN 978-1-84826-823-4. OCLC 691095693.
Ryden, Barbara Sue (2003). Introduction to Cosmology. San Francisco: Addison-Wesley. ISBN 978-0-8053-8912-8. LCCN 2002013176. OCLC 1087978842.
Silk, Joseph (2009). Horizons of Cosmology: Exploring Worlds Seen and Unseen. Templeton Science and Religion Series. Conshohocken, PA: Templeton Press. ISBN 978-1-59947-341-3. LCCN 2009010014. OCLC 818734366.
Singh, Simon (2004). Big Bang: The Origin of the Universe (1st U.S. ed.). New York: Fourth Estate. Bibcode:2004biba.book.....S. ISBN 978-0-00-716220-8. LCCN 2004056306. OCLC 475508230.
Tanabashi, M.; et al. (Particle Data Group) (2018). "Review of Particle Physics". Physical Review D. 98 (3): 1–708. Bibcode:2018PhRvD..98c0001T. doi:10.1103/PhysRevD.98.030001. PMID 10020536.
Tolman, Richard C. (1934). Relativity, Thermodynamics and Cosmology. The International Series of Monographs on Physics. Oxford, UK; London: Clarendon Press; Oxford University Press. ISBN 978-0-486-65383-9. LCCN 34032023. OCLC 919976.
Woolfson, Michael (2013). Time, Space, Stars & Man: The Story of Big Bang (2nd ed.). London: Imperial College Press. ISBN 978-1-84816-933-3. LCCN 2013371163. OCLC 835115510.
Wright, Edward L. (2004). "Theoretical Overview of Cosmic Microwave Background Anisotropy". In Freedman, Wendy L. (ed.). Measuring and Modeling the Universe. Carnegie Observatories Astrophysics Series. Vol. 2. Cambridge, UK: Cambridge University Press. p. 291. arXiv:astro-ph/0305591. Bibcode:2004mmu..symp..291W. ISBN 978-0-521-75576-4. LCCN 2005277053. OCLC 937330165.
Yao, W.-M.; et al. (Particle Data Group) (2006). "Review of Particle Physics" (PDF). Journal of Physics G: Nuclear and Particle Physics. 33 (1): 1–1232. Bibcode:2006JPhG...33....1Y. doi:10.1088/0954-3899/33/1/001. S2CID 117958297. Archived (PDF) from the original on 12 February 2017. Retrieved 16 December 2019.
Further reading
For an annotated list of textbooks and monographs, see Physical cosmology § Textbooks.
Alpher, Ralph A.; Herman, Robert (August 1988). "Reflections on Early Work on 'Big Bang' Cosmology". Physics Today. 41 (8): 24–34. Bibcode:1988PhT....41h..24A. doi:10.1063/1.881126.
Barrow, John D. (1994). The Origin of the Universe. Science Masters. London: Weidenfeld & Nicolson. ISBN 978-0-297-81497-9. LCCN 94006343. OCLC 490957073.
Davies, Paul (1992). The Mind of God: The Scientific Basis for a Rational World. New York: Simon & Schuster. ISBN 978-0-671-71069-9. LCCN 91028606. OCLC 59940452.
Lineweaver, Charles H.; Davis, Tamara M. (March 2005). "Misconceptions about the Big Bang" (PDF). Scientific American. Vol. 292, no. 3. pp. 36–45. Archived (PDF) from the original on 9 October 2019. Retrieved 23 December 2019.
Mather, John C.; Boslough, John (1996). The Very First Light: The True Inside Story of the Scientific Journey Back to the Dawn of the Universe (1st ed.). New York: Basic Books. ISBN 978-0-465-01575-7. LCCN 96010781. OCLC 34357391.
Riordan, Michael; Zajc, William A. (May 2006). "The First Few Microseconds" (PDF). Scientific American. Vol. 294, no. 5. pp. 34–41. Bibcode:2006SciAm.294e..34R. doi:10.1038/scientificamerican0506-34a. Archived (PDF) from the original on 30 November 2014.
Singh, Simon (2005) [First U.S. edition published 2004]. Big Bang: The Origin of the Universe (Harper Perennial; illustrated ed.). New York, New York: Harper Perennial. ISBN 978-0007162215.
Weinberg, Steven (1993) [Originally published 1977]. The First Three Minutes: A Modern View of the Origin of the Universe (Updated ed.). New York: Basic Books. ISBN 978-0-465-02437-7. LCCN 93232406. OCLC 488469247. 1st edition is available from the Internet Archive. Retrieved 23 December 2019.
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