The Big Bang model is the prevailing cosmological theory of the early development of the universe. The major feature of the Big Bang theory is that the universe was once in an extremely hot and dense state that expanded rapidly (a "Big Bang"). This rapid expansion caused the young universe to cool and resulted in its present continuously expanding state. According to recent measurements, scientific evidence, and observations, the original state happened around 13.7 billion years ago (see age of the Universe), which can be referred to as the time that the Big Bang occurred.

Georges Lemaître proposed what became known as the Big Bang theory of the origin of the universe; he called it his "hypothesis of the primeval atom". The framework for the model relies on Albert Einstein's general relativity and on simplifying assumptions (such as homogeneity and isotropy of space). The governing equations had been formulated by Alexander Friedmann. In 1929, Edwin Hubble discovered that the distances to far away galaxies were generally proportional to their redshifts—an idea originally suggested by Lemaître in 1927. Hubble's observation was taken to indicate that all very distant galaxies and clusters have an apparent velocity directly away from our vantage point: the farther away, the higher the apparent velocity.

If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of this theory. On the other hand, these accelerators have limited capabilities to probe into such high energy regimes. There is little evidence regarding the absolute earliest instant of the expansion. Thus, the Big Bang theory cannot and does not provide any explanation for such an initial condition; rather, it describes and explains the general evolution of the universe going forward from that point on. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nucleosynthesis.

Fred Hoyle is credited with coining the term Big Bang during a 1949 radio broadcast. It is popularly reported that Hoyle, who favored an alternative "steady state" cosmological model, intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models. Hoyle later helped considerably in the effort to understand stellar nucleosynthesis, the nuclear pathway for building certain heavier elements from lighter ones. After the discovery of the cosmic microwave background radiation in 1964, and especially when its spectrum (i.e., the amount of radiation measured at each wavelength) was found to match that of thermal radiation from a black body, most scientists were fairly convinced by the evidence that some version of the Big Bang scenario must have occurred.

Motivation and development

The Big Bang theory 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. Ten years later, Alexander Friedmann, a Russian cosmologist and mathematician, derived the Friedmann equations from Albert Einstein's equations of general relativity, showing that the Universe might be expanding in contrast to the static Universe model advocated by Einstein at that time. In 1924, Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies. Independently deriving Friedmann's equations in 1927, Georges Lemaître, a Belgian physicist and Roman Catholic priest, proposed that the inferred recession of the nebulae was due to the expansion of the Universe.

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.

Starting in 1924, Hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 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 recession velocity—now known as Hubble's law. Lemaître had already shown that this was expected, given the Cosmological Principle.

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

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. The other was Lemaître's Big Bang theory, advocated and developed by George Gamow, who introduced big bang nucleosynthesis (BBN) and whose associates, Ralph Alpher and Robert Herman, predicted the cosmic microwave background radiation (CMB). 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. 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 cosmic microwave background radiation in 1964 secured the Big Bang as the best theory of the origin and evolution of the cosmos. Much of the current work in cosmology includes understanding how galaxies form in the context of the Big Bang, understanding the physics of the Universe at earlier and earlier times, and reconciling observations with the basic theory.

Huge strides in Big Bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as COBE, the Hubble Space Telescope and WMAP. 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.

Overview

Timeline of the Big Bang

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. This singularity signals the breakdown of general relativity. How closely we can extrapolate towards the singularity is debated—certainly no closer than the end of the Planck epoch. This singularity is sometimes called "the Big Bang", but the term can also refer to the early hot, dense phase itself, which can be considered the "birth" of our Universe. Based on measurements of the expansion using Type Ia supernovae, measurements of temperature fluctuations in the cosmic microwave background, and measurements of the correlation function of galaxies, the Universe has a calculated age of 13.75 ± 0.11 billion years. The agreement of these three independent measurements strongly supports the ΛCDM model that describes in detail the contents of the Universe.

The earliest phases of the Big Bang are subject to much speculation. In the most common models, the Universe was filled homogeneously and isotropically with an incredibly high energy density, huge temperatures and pressures, and was very rapidly expanding and cooling. Approximately 10⁻³⁷ seconds into the expansion, a phase transition caused a cosmic inflation, during which the Universe grew exponentially. After inflation stopped, the Universe consisted of a quark–gluon plasma, as well as all other elementary particles. 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. 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.

The Universe continued to grow in size 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. After about 10⁻¹¹ seconds, the picture becomes less speculative, since particle energies drop to values that can be attained in particle physics experiments. 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 now no longer high enough to create new proton–antiproton pairs (similarly for neutrons–antineutrons), so a mass annihilation immediately followed, leaving just one in 10¹⁰ of the original protons and neutrons, and none of their antiparticles. 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 (one thousand million; 10⁹; SI prefix giga-) kelvin and the density was about that of air, neutrons combined with protons to form the Universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis. Most protons remained uncombined as hydrogen nuclei. As the Universe cooled, the rest mass 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); hence the radiation decoupled from matter and continued through space largely unimpeded. This relic radiation is known as the cosmic microwave background radiation.

Over a long period of time, the slightly denser regions of the nearly uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today. 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, warm dark matter, hot dark matter and baryonic matter. The best measurements available (from 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), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%. In an "extended model" which includes hot dark matter in the form of neutrinos, then if the "physical baryon density" Ω_bh² is estimated at about 0.023 (this is different from the 'baryon density' Ω_b expressed as a fraction of the total matter/energy density, which as noted above is about 0.046), and the corresponding cold dark matter density Ω_ch² is about 0.11, the corresponding neutrino density Ω_vh² is estimated to be less than 0.0062.

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 apparently permeates all of space. The observations suggest 73% of the total energy density of today's Universe is in this form. When the Universe was very young, it was likely infused with dark energy, but with less space and everything closer together, gravity had the upper hand, and it was slowly braking the expansion. But eventually, after numerous billion years of expansion, the growing abundance of dark energy caused the expansion of the Universe to slowly begin to accelerate. Dark energy in its simplest formulation takes the form of the cosmological constant term in Einstein's field equations of general relativity, but its composition and mechanism are unknown and, more generally, the details of its equation of state and relationship with the Standard Model of particle physics continue to be investigated both observationally and theoretically.

All of this cosmic evolution after the inflationary epoch can be rigorously described and modeled by the ΛCDM model of cosmology, which uses the independent frameworks of quantum mechanics and Einstein's General Relativity. As noted above, there is no well-supported model describing the action prior to 10⁻¹⁵ seconds or so. Apparently a new unified theory of quantum gravitation is needed to break this barrier. Understanding this earliest of eras in the history of the Universe is currently one of the greatest unsolved problems in physics.

Underlying assumptions

The Big Bang theory depends on two major assumptions: the universality of physical laws, and the cosmological principle. The cosmological principle states that on large scales the Universe is homogeneous and isotropic.

These ideas were initially taken as postulates, but today there are efforts to test each of them. For example, the first assumption has been tested by observations showing that largest possible deviation of the fine structure constant over much of the age of the universe is of order 10⁻⁵. Also, general relativity has passed stringent tests on the scale of the solar system and binary stars while extrapolation to cosmological scales has been validated by the empirical successes of various aspects of the Big Bang theory.

If the large-scale Universe appears isotropic as viewed from Earth, 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 CMB. The Universe has been measured to be homogeneous on the largest scales at the 10% level.

FLRW metric

General relativity describes spacetime by a metric, which determines the distances that separate nearby points. The points, which can be galaxies, stars, or other objects, themselves are specified using a coordinate chart or "grid" that is laid down over all spacetime. The cosmological principle implies that the metric should be homogeneous and isotropic on large scales, which uniquely singles out the Friedmann–Lemaître–Robertson–Walker metric (FLRW metric). This metric contains a scale factor, which describes how the size of the Universe changes with time. This enables a convenient choice of a coordinate system to be made, called comoving coordinates. In this coordinate system, the grid expands along with the Universe, and objects that are moving only due to the expansion of the Universe remain at fixed points on the grid. While their coordinate distance (comoving distance) remains constant, the physical distance between two such comoving points expands proportionally with the scale factor of the Universe.

The Big Bang is not an explosion of matter moving outward to fill an empty universe. Instead, space itself expands with time everywhere and increases the physical distance between two comoving points. Because the FLRW metric assumes a uniform distribution of mass and energy, it applies to our Universe only on large scales—local concentrations of matter such as our galaxy are gravitationally bound and as such do not experience the large-scale expansion of space.

Horizons

An important feature of the Big Bang spacetime is the presence of 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 had time to reach us. 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. 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.

Observational evidence

The earliest and most direct kinds of observational evidence are the Hubble-type expansion seen in the redshifts of galaxies, the detailed measurements of the cosmic microwave background, the abundance of light elements (see Big Bang nucleosynthesis), and today also the large scale distribution and apparent evolution of galaxies which are predicted to occur due to gravitational growth of structure in the standard theory. These are sometimes called "the four pillars of the Big Bang theory".

Hubble's law and the expansion of space

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 lines 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: :v = H₀D, where

v is the recessional velocity of the galaxy or other distant object,

D is the comoving distance to the object, and

H₀ is Hubble's constant, measured to be km/s/Mpc by the WMAP probe.

Hubble's law has two possible explanations. Either we are at the center of an explosion of galaxies—which is untenable given the Copernican Principle—or the Universe is uniformly expanding everywhere. This universal expansion was predicted from general relativity by Alexander Friedmann in 1922 and Georges Lemaître in 1927, well before Hubble made his 1929 analysis and observations, and it remains the cornerstone of the Big Bang theory as developed by Friedmann, Lemaître, Robertson and Walker.

The theory requires the relation v = HD to hold at all times, where D is the comoving distance, v is the recessional velocity, and v, H, and D vary as the Universe expands (hence we write H₀ 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. However, the redshift is not a true Doppler shift, but rather the result of the expansion of the Universe between the time the light was emitted and the time that it was detected.

That space is undergoing metric expansion is shown by direct observational evidence of the Cosmological Principle and the Copernican Principle, which together with Hubble's law have no other explanation. Astronomical redshifts are extremely isotropic and homogenous, supporting the Cosmological Principle that the Universe looks the same in all directions, along with much other evidence. If the redshifts were the result of an explosion from a center distant from us, they would not be so similar in different directions.

Measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems in 2000 proved the Copernican Principle, that the Earth is not in a central position, on a cosmological scale. Radiation from the Big Bang was demonstrably warmer at earlier times throughout the Universe. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the Universe is experiencing a metric expansion, and excludes the possibility that we are near the unique center of an explosion.

Cosmic microwave background radiation

During the first few days of the Universe, the Universe was in full thermal equilibrium, with photons being continually emitted and absorbed, giving the radiation a blackbody spectrum. As the Universe expanded, it cooled to a temperature at which photons could no longer be created or destroyed. The temperature was still high enough for electrons and nuclei to remain unbound, however, and photons were constantly "reflected" from these free electrons through a process called Thomson scattering. Because of this repeated scattering, the early Universe was opaque to light.

When the temperature fell to a few thousand Kelvin, electrons and nuclei began to combine to form atoms, a process known as recombination. Since photons scatter infrequently from neutral atoms, radiation decoupled from matter when nearly all the electrons had recombined, at the epoch of last scattering, 379,000 years after the Big Bang. These photons make up the CMB that is observed today, and the observed pattern of fluctuations in the CMB is a direct picture of the Universe at this early epoch. The energy of photons was subsequently redshifted by the expansion of the Universe, which preserved the blackbody spectrum but caused its temperature to fall, meaning that the photons now fall into the microwave region of the electromagnetic spectrum. The radiation is thought to be observable at every point in the Universe, and comes from all directions with (almost) the same intensity.

In 1964, Arno Penzias and Robert Wilson accidentally discovered the cosmic background radiation while conducting diagnostic observations using a new microwave receiver owned by Bell Laboratories. Their discovery provided substantial confirmation of the general CMB predictions—the radiation was found to be isotropic and consistent with a blackbody spectrum of about 3 K—and it pitched the balance of opinion in favor of the Big Bang hypothesis. Penzias and Wilson were awarded a Nobel Prize for their discovery.

thumb|left|The cosmic microwave background spectrum measured by the FIRAS instrument on the [[COBE|COBE satellite is the most-precisely measured black body spectrum in nature. The data points and error bars on this graph are obscured by the theoretical curve.]] In 1989, NASA launched the Cosmic Background Explorer satellite (COBE), and the initial findings, released in 1990, were consistent with the Big Bang's predictions regarding the CMB. COBE found a residual temperature of 2.726 K and in 1992 detected for the first time the fluctuations (anisotropies) in the CMB, at a level of about one part in 10⁵. John C. Mather and George Smoot were awarded the Nobel Prize for their leadership in this work. 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 Universe to be almost spatially flat by measuring the typical angular size (the size on the sky) of the anisotropies. (See shape of the Universe.)

In early 2003, the first results of the Wilkinson Microwave Anisotropy Probe (WMAP) were released, yielding what were at the time the most accurate values for some of the cosmological parameters. This spacecraft also disproved several specific cosmic inflation models, but the results were consistent with the inflation theory in general, it confirms too that a sea of cosmic neutrinos permeates the Universe, a clear evidence that the first stars took more than a half-billion years to create a cosmic fog. A new space probe named Planck, with goals similar to WMAP, was launched in May 2009. It is anticipated to soon provide even more accurate measurements of the CMB anisotropies. Many other ground- and balloon-based experiments are also currently running; see Cosmic microwave background experiments.

The background radiation is exceptionally smooth, which presented a problem in that conventional expansion would mean that photons coming from opposite directions in the sky were coming from regions that had never been in contact with each other. The leading explanation for this far reaching equilibrium is that the Universe had a brief period of rapid exponential expansion, called inflation. This would have the effect of driving apart regions that had been in equilibrium, so that all the observable Universe was from the same equilibrated region.

Abundance of primordial elements

Using the Big Bang model it is possible to calculate the concentration of helium-4, helium-3, deuterium and lithium-7 in the Universe as ratios to the amount of ordinary hydrogen, H. All the abundances depend on a single parameter, the ratio of photons to baryons, which itself can be calculated independently from the detailed structure of CMB fluctuations. The ratios predicted (by mass, not by number) are about 0.25 for /, about 10⁻³ for /, about 10⁻⁴ for / and about 10⁻⁹ for /.

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 , and a factor of two off for ; 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. Indeed there is no obvious reason outside of the Big Bang that, for example, the young Universe (i.e., before star formation, as determined by studying matter supposedly free of stellar nucleosynthesis products) should have more helium than deuterium or more deuterium than , and in constant ratios, too.

Galactic evolution and distribution

Detailed observations of the morphology and distribution of galaxies and quasars provide strong evidence for the Big Bang. A combination of observations and theory suggest that the first quasars and galaxies formed about a billion years after the Big Bang, and since then larger structures have been forming, such as galaxy clusters and superclusters. 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.

Other lines of evidence

After some controversy, the age of Universe as estimated from the Hubble expansion and the CMB is now in good agreement with (i.e., slightly larger than) 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.

The prediction that the CMB temperature was higher in the past has been experimentally supported by observations of temperature-sensitive emission lines in gas clouds at high redshift. This prediction also implies that the amplitude of the Sunyaev–Zel'dovich effect in clusters of galaxies does not depend directly on redshift; this seems to be roughly true, but unfortunately the amplitude does depend on cluster properties which do change substantially over cosmic time, so a precise test is impossible.

==Features, issues and problems== While scientists now prefer the Big Bang model over other cosmological models, the scientific community was once divided between supporters of the Big Bang and those of alternative cosmological models. Throughout the historical development of the subject, problems with the Big Bang theory were posed in the context of a scientific controversy regarding which model could best describe the cosmological observations. With the overwhelming consensus in the community today supporting the Big Bang model, many of these problems are remembered as being mainly of historical interest; the solutions to them have been obtained either through modifications to the theory or as the result of better observations.

The core ideas of the Big Bang—the expansion, the early hot state, the formation of helium, the formation of galaxies—are derived from many observations that are independent from any cosmological model; these include the abundance of light elements, the cosmic microwave background, large scale structure, and the Hubble diagram for Type Ia supernovae.

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 to the most active laboratory investigations. Remaining issues, such as the cuspy halo problem and the dwarf galaxy problem of cold dark matter, are not fatal to the dark matter explanation as solutions to such problems exist which involve only further refinements of the theory. 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.

On the other hand, inflation and baryogenesis remain somewhat more speculative features of current Big Bang models: they explain important features of the early universe, but could be replaced by alternative ideas without affecting the rest of the theory. Discovering the correct explanations for such phenomena are some of the remaining unsolved problems in physics.

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. 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.

A resolution to this apparent inconsistency is offered by inflationary 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.

Heisenberg's uncertainty principle predicts that during the inflationary phase there would be quantum thermal fluctuations, which would be magnified to cosmic scale. These fluctuations serve as the seeds of all current structure in the Universe. Inflation predicts that the primordial fluctuations are nearly scale invariant and Gaussian, which has been accurately confirmed by measurements of the CMB.

If inflation occurred, exponential expansion would push large regions of space well beyond our observable horizon.

Flatness/oldness problem

The flatness problem (also known as the oldness problem) is an observational problem associated with a Friedmann–Lemaître–Robertson–Walker metric. 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. The problem is that any small departure from the critical density grows with time, and yet the Universe today remains very close to flat. Given that a natural timescale for departure from flatness might be the Planck time, 10⁻⁴³ seconds, the fact that the Universe has reached neither a Heat Death nor a Big Crunch after billions of years requires some explanation. For instance, even at the relatively late age of a few minutes (the time of nucleosynthesis), the Universe density must have been within one part in 10¹⁴ of its critical value, or it would not exist as it does today.

A resolution to this problem is offered by inflationary theory. During the inflationary period, spacetime expanded to such an extent that its curvature would have been smoothed out. Thus, it is theorized that inflation drove the Universe to a very nearly spatially flat state, with almost exactly the critical density.

Magnetic monopoles

The magnetic monopole objection was raised in the late 1970s. Grand unification theories 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 searches have never found any monopoles. This problem is also resolved by cosmic inflation, which removes all point defects from the observable Universe in the same way that it drives the geometry to flatness.

A resolution to the horizon, flatness, and magnetic monopole problems alternative to cosmic inflation is offered by the Weyl curvature hypothesis.

Baryon asymmetry

It is not yet understood why the Universe has more matter than antimatter. 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 matter. An unknown process called "baryogenesis" created 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. All these conditions occur in the Standard Model, but the effect is not strong enough to explain the present baryon asymmetry.

Globular cluster age

In the mid-1990s, observations of globular clusters appeared to be inconsistent with the Big Bang. Computer simulations that matched the observations of the stellar populations of globular clusters suggested that they were about 15 billion years old, which conflicted with the 13.7 billion year age of the Universe. This issue was generally resolved in the late 1990s when new computer simulations, which included the effects of mass loss due to stellar winds, indicated a much younger age for globular clusters. There still remain some questions as to how accurately the ages of the clusters are measured, but it is clear that these objects are some of the oldest in the Universe.

Dark matter

During the 1970s and 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 was initially controversial, it is now indicated by numerous observations: the anisotropies in the CMB, galaxy cluster velocity dispersions, large-scale structure distributions, gravitational lensing studies, and X-ray measurements of galaxy clusters.

The evidence for dark matter comes from its gravitational influence on other matter, and 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.

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". Dark energy is indicated by several other lines of evidence. 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. Since dark energy does not cluster in the usual way it is the best explanation for the "missing" energy density. Dark energy is also required by two geometrical measures of the overall curvature of the Universe, one using the frequency of gravitational lenses, and the other using the characteristic pattern of the large-scale structure as a cosmic ruler.

Negative pressure is a property of vacuum energy, but the exact nature of dark energy remains one of the great mysteries of the Big Bang. Possible candidates include a cosmological constant and quintessence. Results from the WMAP team in 2008, which combined data from the CMB and other sources, indicate that the contributions to mass/energy density in the Universe today are approximately 73% dark energy, 23% dark matter, 4.6% regular matter and less than 1% neutrinos. 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.

In the ΛCDM, the best current model of the Big Bang, dark energy is explained by the presence of a cosmological constant in the general theory of relativity. However, the size of the constant that properly explains dark energy is surprisingly small relative to naive estimates based on ideas about quantum gravity. Distinguishing between the cosmological constant and other explanations of dark energy is an active area of current research.

The future according to the Big Bang theory

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 that was similar to that in which it started—a Big Crunch. 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 as all the interstellar gas in each galaxy is consumed; stars would burn out leaving white dwarfs, neutron stars, and black holes. Very gradually, collisions between these would result in mass accumulating into larger and larger black holes. The average temperature of the Universe would asymptotically approach absolute zero—a Big Freeze. Moreover, if the proton were 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.

Modern observations of accelerated 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, would remain together, and they too would be subject to heat death, as the Universe expands and cools. Other explanations of dark energy—so-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.

Speculative physics beyond Big Bang theory

While the Big Bang model is well established in cosmology, it is likely to be refined in the future. Little is known about the earliest moments of the Universe's history. The Penrose–Hawking singularity theorems require the existence of a singularity at the beginning of cosmic time. However, these theorems assume that general relativity is correct, but general relativity must break down before the Universe reaches the Planck temperature, and a correct treatment of quantum gravity may avoid the singularity.

Some proposals, each of which entails untested hypotheses, are: models including the Hartle–Hawking no-boundary condition in which the whole of space-time is finite; the Big Bang does represent the limit of time, but without the need for a singularity. Big Bang lattice model states that the Universe at the moment of the Big Bang consists of an infinite lattice of fermions which is smeared over the fundamental domain so it has both rotational, translational and gauge symmetry. The symmetry is the largest symmetry possible and hence the lowest entropy of any state.

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 endlessly cycles from one process to the other. chaotic 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.

Proposals in the last two categories see the Big Bang as an event in a much larger and older Universe, or multiverse, and not the literal beginning.

Religious interpretations

The Big Bang is a scientific theory, and as such is dependent on its agreement with observations. But as a theory which addresses the origins of reality, it has always carried theological and philosophical implications, most notably, the concept of creation ex nihilo (Latin meaning "out of nothing"). 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. This perception was enhanced by the fact that the originator of the Big Bang theory, Monsignor Georges Lemaître, was a Roman Catholic priest. Pope Pius XII declared, at the November 22, 1951 opening meeting of the Pontifical Academy of Sciences, that the Big Bang theory accorded with the Catholic concept of creation. Conservative Protestant Christian denominations have also welcomed the Big Bang theory as supporting a historical interpretation of the doctrine of creation.

Since the acceptance of the Big Bang as the dominant physical cosmological paradigm, there have been a variety of reactions by religious groups as to its implications for their respective religious cosmologies. Some accept the scientific evidence at face value, while others seek to reconcile the Big Bang with their religious tenets, and others completely reject or ignore the evidence for the Big Bang theory.

Notes

References

Books

Further reading

:For an annotated list of textbooks and monographs, see physical cosmology.

External links

Big bang model with animated graphics

Evidence for the Big Bang

Category:Physical cosmology Category:Astrophysics theories *Main Category:Universe

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Coordinates	3°8′51″N101°41′36″N
name	Miley Cyrus
background	solo_singer
full name	Miley Ray Cyrus
birth name	Destiny Hope Cyrus
birth date	November 23, 1992
birth place
genre	Pop, pop rock, country pop, dance
occupation	Actress, author, entrepreneur, fashion designer, singer-songwriter, musician, dancer
instrument	Vocals, guitar, piano
years active	2001–present
label	Walt Disney, Hollywood
associated acts	Hannah Montana, Disney's Friends for Change, Billy Ray Cyrus
url	100pxSignature of Miley Cyrus.
notable instruments	}}

Miley Ray Cyrus (born Destiny Hope Cyrus; November 23, 1992) is an American actress and pop singer-songwriter. She achieved wide fame for her role as Miley Stewart/Hannah Montana on the Disney Channel sitcom Hannah Montana. Cyrus recorded music for the soundtracks, Hannah Montana (2006) and Hannah Montana 2/Meet Miley Cyrus (2007), released by Walt Disney Records. With the success of the Hannah Montana franchise she established herself as a teen idol. In 2007, Cyrus signed to Hollywood Records to pursue a solo career. She embarked upon the Best of Both Worlds Tour the same year, in which she performed as both herself and in character as Hannah Montana. The tour was eventually turned into a high-grossing concert film entitled Hannah Montana & Miley Cyrus: Best of Both Worlds Concert (2008). In July 2008, Cyrus released her first solo album, Breakout (2008), which was commercially successful.

She began her foray into film by providing the voice of "Penny" in the animated film Bolt (2008). Cyrus earned a nomination for the Golden Globe Award for Best Original Song for her performance of Bolts theme song, "I Thought I Lost You". She also reprised her role as Miley Stewart/Hannah Montana in Hannah Montana: The Movie (2009). The Hannah Montana: The Movie soundtrack introduced her to new audiences within country and adult contemporary markets.

She began to cultivate an adult image in 2009 with the release of The Time of Our Lives (2009), an extended play which presented a more mainstream pop sound, and by filming The Last Song (2010), a coming-of-age drama film. The former included Cyrus's best-selling single, "Party in the U.S.A." (2009). A studio album titled Can't Be Tamed was released in 2010 and presents a new dance-pop sound. The music video and lyrics of the album's lead single, "Can't Be Tamed", portrays a more sexualized image for the entertainer. Cyrus ranked number thirteen on Forbes 2010 Celebrity 100. In April 2011, Cyrus was named the 64th hottest woman in the world on Maxim's Hot 100. In May 2011, Cyrus was also named the 89th sexiest woman in the world on FHM's 100 Sexiest Women in the world.

Early life

Cyrus was born on November 23, 1992 in Nashville, Tennessee to Letitia Jean "Tish" (née Finley) and country singer Billy Ray Cyrus. Her parents named her Destiny Hope because they believed that she would accomplish great things with her life. They gave her the nickname "Smiley", which was later shortened to "Miley", because she smiled so often as a baby. Cyrus suffers from a mild heart condition causing tachycardia which, though not dangerous, is often bothersome.

Against the wishes of her father's record company, Cyrus's parents secretly married a year after Cyrus's birth on December 28, 1993. Tish had two children from a previous relationship: Trace and Brandi. Billy Ray adopted Trace and Brandi when they were young. She has a half-brother, Christopher Cody, Billy Ray's son from a brief relationship, born the same year as Miley; he grew up with his mother in South Carolina. Tish and Billy Ray had two more children, Braison and Noah. Cyrus's godmother is entertainer Dolly Parton. Cyrus was very close to her paternal grandfather, Democratic politician Ronald Ray Cyrus. Cyrus has paid her grandfather several tributes since his death in 2006, including eventually changing her middle name to "Ray". According to Cyrus's father, "A lot of people say Miley changed her name to Miley Ray because of Billy Ray, but that's not true. She did that in honor of my dad, because the two of them just loved each other to pieces."

Cyrus grew up on a farm in Franklin, Tennessee, approximately an hour away from Nashville, and attended Heritage Elementary School. She was raised Christian and was baptized in a Southern Baptist church prior to moving to Hollywood in 2005. She attended church regularly while growing up and wore a purity ring. Several of Cyrus's siblings also eventually entered the entertainment business: Trace became a vocalist and guitarist for the electronic pop band Metro Station, Noah became an actress, and Brandi became a guitarist.

Career

2001–05: Career beginnings

In 2001, when Cyrus was eight, she and her family moved to Toronto, Canada while her father filmed the television series Doc. Cyrus said watching her father film the show inspired her to pursue acting. After Billy Ray took her to see a 2001 Mirvish production of Mamma Mia! at the Royal Alexandra Theatre, Cyrus grabbed his arm and told him, "This is what I want to do, daddy. I want to be an actress." She began taking singing and acting classes at the Armstrong Acting Studio in Toronto. In her first role, Cyrus played a girl named Kylie on Doc. In 2003, Cyrus was credited under her birth name for her role as "Young Ruthie" in Tim Burton's Big Fish.

At age 11, Cyrus learned about the casting for what became Hannah Montana, a Disney Channel children's television series about a school girl with a secret double life as a teen pop star. Cyrus sent in a tape auditioning for the show's best friend role, but received a call asking her to audition for the lead, "Chloe Stewart". After sending in a new tape and flying to Hollywood for further auditions, Cyrus was told that she was too young and too small for the part. However, her persistence and ability to sing in addition to act led the show's producers to invite her back for further auditions. Cyrus eventually received the lead, renamed "Miley Stewart" after herself, at the age of twelve. During this time, she also auditioned with Taylor Lautner for the feature film The Adventures of Sharkboy and Lavagirl in 3-D and it came down to her and another actress, but Cyrus started doing Hannah Montana instead.

As Cyrus's career took off, Tish Cyrus made several critical decisions regarding her daughter's representation. She signed Cyrus with Mitchell Gossett, director of the youth division at Cunningham Escott Slevin Doherty. Gossett, who specializes in creating child stars, had arranged for Cyrus's auditions for Hannah Montana and is credited with "discovering" her. For Cyrus's music career, Tish followed the advice of Dolly Parton, Cyrus's godmother and a singer herself, and signed Cyrus with Jason Morey of Morey Management Group. "Dolly said the Moreys are people you can trust around your daughter," Tish Cyrus recalls, "and she said they have good morals, which is not always the case in this business." According to trade magazine The Hollywood Reporter, Parton's advice was "the best advice [Tish] could [have gotten] on who should rep her daughter." Tish also recruited Billy Ray's business manager to manage her daughter's finances. Tish herself continues to co-manage or produce many of Cyrus's career decisions. For her education, Cyrus enrolled at Options for Youth Charter Schools and studied with a private tutor on the set of her television show.

2006–07: Hannah Montana and Hannah Montana 2: Meet Miley Cyrus

Hannah Montana became an instant hit and propelled Cyrus to teen idol status, according to The Daily Telegraph. The series premiered on March 26, 2006 to the largest audience ever for a Disney Channel show and soon became one of the highest-rated series on basic cable, elevating Cyrus's wealth and fame along with it. Time magazine reports that Cyrus's "phenom[enal]" success is due partially to her talent and partially to "Disney learning to use its vast, multimedia holdings" and market Cyrus and Hannah Montana appropriately. Cyrus eventually became the first artist to have deals in television, film, consumer products, and music within The Walt Disney Company.

Cyrus's first single was "The Best of Both Worlds", the theme song to Hannah Montana, which was released on March 28, 2006. "The Best of Both Worlds" is credited to "Hannah Montana", the pop star Cyrus portrays on the series by the same name. As with other songs credited to Montana, Cyrus typically dressed as the character when performing the song live. Cyrus's first release under her own name was a cover of James Baskett's "Zip-a-Dee-Doo-Dah", released on April 4, 2006 on the fourth edition of DisneyMania. Dressed as Hannah Montana, Cyrus opened for The Cheetah Girls on twenty dates of their The Party's Just Begun Tour, beginning on September 15, 2006. On October 24 of same year, Walt Disney Records released the first Hannah Montana soundtrack. Of the nine tracks on the soundtrack performed by Cyrus, eight were credited to "Hannah Montana" and one, a duet with her father titled "I Learned from You", was credited to Cyrus as herself. The album peaked at number one on the U.S. Billboard 200 chart.

The second season of Hannah Montana premiered on April 23, 2007, and ran until October 12, 2008. Cyrus signed a four-album deal with Disney-owned Hollywood Records and, on June 26, 2007, released a double-disc album. The first disc was the soundtrack to the second season of Hannah Montana, while the second, titled Meet Miley Cyrus, was Cyrus's debut album credited to her own name. The double-disc album peaked at number one on the Billboard 200 and was later certified three times platinum by the Recording Industry Association of America (RIAA). Meet Miley Cyrus generated "See You Again", Cyrus's first single to be released under her own name and her first top ten hit on the Billboard Hot 100. In Fall 2007, Cyrus launched her first tour, the Best of Both Worlds Tour, to promote Meet Miley Cyrus and the Hannah Montana soundtracks. With the Jonas Brothers, Aly & AJ, and Everlife as her opening acts, Cyrus toured from October 17, 2007 to January 31, 2008 with stops in the U.S. and Canada. Tickets sold out in minutes and were scalped for up to $2,500 and an average of $214, well above their $26–$65 face value. A Ticketmaster official commented, "Hell hath no fury like the parent of a child throwing a tantrum. People who have been in this business for a long time are watching what's happening, and they say there hasn't been a demand of this level or intensity since The Beatles or Elvis."

2008–09: Breakout, transitions and film career launch

After the end of the Best of Both Worlds Tour in January 2008, Walt Disney Pictures released Hannah Montana & Miley Cyrus: Best of Both Worlds Concert, a 3D concert film of the tour, on February 1, 2008 for what was expected to be a one-week run. The film earned over $31 million at the box-office and an average of $42,000 per theater, twice the expected total, convincing Disney executives to extend the release for an indefinite run. "We don't want to turn away kids from the theaters who couldn't get into the concerts," said Chuck Viane, Disney's chief of distribution. The film's soundtrack was released by Walt Disney Records/Hollywood Records on March 11, 2008 and peaked at number three on the Billboard 200.

On July 22, 2008, Cyrus released her second studio album under her own name, entitled Breakout. Cyrus said Breakout was inspired by "what's been going on in my life in the past year." Cyrus co-wrote eight out of twelve songs on the album. "Songwriting is what I really want to do with my life forever, [...] I just hope this record showcases that, more than anything, I'm a writer." The album debuted at #1 on the U.S. Billboard 200 chart and its lead single, "7 Things", peaked at number 9 on the Billboard Hot 100. She hosted the 2008 CMT Music Awards with her father in April and the 2008 Teen Choice Awards by herself in August. Cyrus provided the voice of Penny in the 2008 computer-animated film Bolt, which was released on November 21, 2008 to critical acclaim. Cyrus also co-wrote and recorded the song "I Thought I Lost You" as a duet with John Travolta for the film, for which she received a Golden Globe nomination. In September 2009, she participated in the charity single "Just Stand Up!" in support of the anti-cancer campaign Stand Up to Cancer and in the City of Hope Benefit Concert in support of cancer research and training programs. She also became involved in Disney's Friends for Change, an environmentalist group, for which she recorded the charity single "Send It On" along with several other Disney Channel stars.

Cyrus had already begun transitioning to a more grown-up image in late 2008, when her representatives negotiated a deal for novelist Nicholas Sparks to write the screenplay and novel basis for a film that would serve as a star vehicle for Cyrus by introducing her to audiences older than the young fans she had gained through Hannah Montana. Sparks and co-writer Jeff Van Wie developed The Last Song. It was important to Cyrus that she not be type cast as a singer: "I didn't want to be a singer in another film. I don't want to do that anymore. You have no idea how many musicals show up on my door. I want to do something a little more serious." In March 2009, Cyrus published Miles to Go, a memoir co-written by Hilary Liftin chronicling her life through age sixteen. Cyrus starred as Miley Stewart/Hannah Montana in Hannah Montana: The Movie, released April 10, 2009. Both the film and its soundtrack, which contained twelve songs performed by Cyrus, achieved commercial success. The soundtrack's lead single, "The Climb", became a Top 40 hit in twelve countries and introduced Cyrus to listeners outside her typical teen pop audience. Cyrus had considered ending Hannah Montana after its third season, which finished production on June 5, 2009, but Disney retained and exercised its option for a fourth season.

Production on The Last Song lasted from June 15, 2009 to August 18, 2009. In between, Cyrus launched the third Hannah Montana soundtrack, recorded the extended play The Time of Our Lives, and released the EP's lead single, "Party in the U.S.A." Cyrus said The Time of Our Lives "is a transitioning album. [...] really to introduce people to what I want my next record to sound like and with time I will be able to do that a little more." "Party in the U.S.A." debuted at number two on the Billboard Hot 100 for her best-ever ranking on the chart. The Time of Our Lives was released in conjunction with a clothing line co-designed by Cyrus and Max Azria for Walmart.

From September 14, 2009 to December 29, 2010, Cyrus toured on her Wonder World Tour to promote Breakout and The Time of Our Lives. On December 7, 2009, Cyrus performed for Queen Elizabeth II and numerous other members of the British Royal Family at the Royal Variety Performance in Blackpool, North West England.

2010–present: Can't Be Tamed, focus on film career and fourth studio album

Production on the fourth and final season of Hannah Montana began on January 18, 2010. In the aftermath of the 2010 Haiti earthquake, Cyrus appeared on the charity singles "We Are the World: 25 for Haiti" and "Everybody Hurts". Her third studio album, Can't Be Tamed, was released on June 21, 2010. The album's first single is the title track, "Can't Be Tamed". The single was released for sale on May 18, 2010 and entered the Billboard Hot 100 at number eight. Cyrus's costumes and dances while promoting Can't Be Tamed were also considerably more provocative than previous performances, arousing media criticism. After releasing the album, Cyrus intends to take a break from the music industry in order to focus on her film career. She commented, "I've not taken, like, acting lessons or anything, but it doesn't mean I don't need to because I'm sure I do [...] I'm probably going to go book an acting coach." Cyrus has also decided to opt out of college for the same reason, saying "I'm a firm believer that you can go back at any age you want, because my Grandma went back to college at 62 [...] For right now, I really want to focus on my career. I've worked hard to get to where I am now, and I want to enjoy it while it lasts."

Cyrus starred in The Last Song, which was released on March 31, 2010, and received generally poor reviews, as did Cyrus's performance. Nonetheless, the film was commercially successful, grossing more than $88 million at the worldwide box office. According to box-office analyst Exhibitor Relations, the film marked "a successful transition to adult roles for Miley Cyrus." The fourth and final season of Hannah Montana began airing on Disney Channel on July 11, 2010 and was ended on January 16, 2011. Cyrus filmed two more films, LOL: Laughing Out Loud and So Undercover in 2010. In LOL, a remake of a 2008 French teen comedy, Cyrus plays "a daughter who is involved with all the wrong kids, doing drugs, failing school, but [...whose] mother has her on this perfect pedestal" and says "[She] just fell in love with the story." Miley's character loses her virginity, smokes cannabis, gets wasted and kisses two girlfriends on the lips. She will also star in So Undercover, an action comedy film. Cyrus will play the part of "a tough, street-smart private eye hired by the FBI to go undercover in a college sorority." She learned street fighting for the role.

Despite her earlier announcement that she'd be focusing more on acting in the future, in February 2011, Cyrus confirmed she had no films lineup and was going to go on tour. On April 29, 2011, Cyrus embarked on her international Gypsy Heart Tour in South America and ended the tour on July 2, 2011 in Australia. Cyrus hosted Saturday Night Live on March 5, 2011, where she performed in several sketches. She also sang a brief song about her several controversies, such as the bong incident, the photo of her friend and she eating a Twizzler, and the "pole dance" on a hotel pole at the Teen Choice Awards, stating "I'm sorry that I'm not perfect." In March 2011, father Billy Ray Cyrus confirmed on talk show, The View, that Miley had been in talks with producer Dr. Luke on a new album. In July 2011, it was announced that she would record her fourth studio album and she has no plans to sign onto any other film projects. However, it was reported on August 2, 2011 by Contact Music that Cyrus has signed on to star in a comedy in which she plays a woman who broke a promise to God.

Earnings

In 2008, Cyrus earned $25 million, up from her earnings of $18 million in 2007, and was ranked number 35 on Forbes magazine's "Celebrity 100" list. Parade magazine reported she was the richest teenage celebrity and that her franchise would be worth approximately $1 billion by the end of the year. In 2009, Forbes ranked her #29 on the Celebrity 100 and reported she had earned a total of $25 million. Then Cyrus got ranked number thirteen on Forbes 2010 Celebrity 100 ranking $48 million. From the $48 million she made between June 2009 to June 2010 made her the no. 4 highest earners under 30 and the youngest on the list. between June 2010 and June 2011, Cyrus earned $54 million.

From working on Hannah Montana, Cyrus got paid $15,000 per episode she did on the hit show, making her the 6th highest paid child star on television behind fellow Disney stars Dylan and Cole Sprouse and Keke Palmer with $20,000 for their shows. Also, she is behind friend and Disney star Selena Gomez that makes $25,000 per episode of her show, Nick star Miranda Cosgrove with $180,000 per episode of her show, and one time co-star Angus T. Jones that got paid $250,000 for each episode of his show. Though she had not got paid as much as other Disney stars,when she was 17 she was named #19 on the "Top 20 World's Richest Female Singers Of All Time" list with over $100 million in 5 years active throughout her career, which made her the youngest female artist on the list. In 2011, she was named #1 on the "Top 10 Richest Teens in Hollywood" with $120 million.

Personal life and image

In an interview, friend and actor Tyler Posey stated that he and Cyrus met on the set of the show Doc, and that they shared their first kiss on the show. He then stated that he and Cyrus dated for two years and then broke up when they were 11.

Cyrus told Seventeen magazine that she and Nick Jonas had dated for two years and "were in love", but were "fighting a lot" by the end. After the break-up, Cyrus says that she initially "rebell[ed] against everything Nick wanted me to be. And then I was like, I've got to be by myself for now, and just figure out who I really am."

In February 2008, Cyrus and her friend opened a YouTube account and began posting videos of what they called The Miley and Mandy Show. The show, described as a "YouTube hit," is said to be filmed for fun by Cyrus and Jiroux and to be entirely their work, with Cyrus and Jiroux editing the footage together.

With Cyrus's increased success came increased media attention. In a May 2008 interview with The Los Angeles Times, Francois Navarre, the proprietor of the X17 photo agency, said Cyrus's market value had picked up considerably after the Vanity Fair photo controversy: "She's started to sell more. [...] It used to be $300, and now it's $2,000 for a picture." Estimates for a picture of the then-15 year old's first kiss ranged from $30,000 to $150,000. Navarre noted that Cyrus rarely behaved against her wholesome image or went out without a parent and stated, "She has people waiting for the moment she starts to be less traditional. [...] It's natural. Any teenager. But it's going to come very fast. [...] As soon as her mom lets her go out by herself. It's going to start to be interesting." Time magazine included her on the 2008 Time 100, the magazine's list of the 100 most influential people in the world. Her write-up was written by former child star Donny Osmond, who warned, "As an idol to tweens the world over, singer-actress Miley Cyrus, 15, is riding a huge tidal wave at the pinnacle of her career; this is as it should be. I hope she enjoys it. [...] Within three to five years, Miley will have to face adulthood. [...] As she does, she'll want to change her image, and that change will be met with adversity."

Cyrus celebrated her 16th birthday at Disneyland with a charity fundraiser for Youth Service America, a youth volunteer service organization.

At the end of 2009, Billboard magazine ranked Cyrus the fourth best-selling female artist and the fifth best-selling singer overall.

In June 2009, Cyrus ended her nine-month relationship with model Justin Gaston shortly before flying to Georgia to film The Last Song. While filming later that month, Cyrus began dating her co-star in The Last Song, Australian actor Liam Hemsworth. She later called him her "first serious boyfriend". In August 2010, it was confirmed that her relationship with Hemsworth had ended. Cyrus and Hemsworth were seen together a month later, and were reportedly back together. It was announced in early November that the couple had split again. On March 31, 2011, Miley Cyrus and Liam Hemsworth have reportedly rekindled their relationship. On June 20, Cyrus confirmed in a interview on the DirtTv in Australia that she and Hemsworth are still rocking and still are together.

On October 26, 2010, less than a month before Cyrus's eighteenth birthday, her father Billy Ray Cyrus filed for divorce from her mother in Tennessee, citing irreconcilable differences. In a statement made to People the next day announcing the split, the couple said, "As you can imagine, this is a very difficult time for our family... We are trying to work through some personal matters. We appreciate your thoughts and prayers." However, on March 18, 2011, Cyrus's father announced on The View that he had dropped the divorce.

Cyrus is the youngest recording artist ever with four #1 albums in less than 3 years.

In June 2011, Cyrus was named by the Rolling Stones magazine a queen of pop, she was named #8 based on album sales selling 2.027 million copies. also, she was named #7 based on digital tracks selling 14.763 million digital copies, #5 based on youtube views with 784,667,358 views, #12 based on radio airplay with 216 airplay's, #11 based on Billboard hot 100 appearances with 164.2 points, and #9 based on social networking with 14.9 million Facebook likes, and 1.4 million Twitter followers. lastly, she was named #6 based off the gross of her tours with 66.5 million dollars in grossing, #14 based off award wins, in this case the Teen Choice Awards did not count and only mainstream-awards counted such as the Grammy Awards and awards like that in the music category, #14 based on album reviews. out of all the rankings for the categories, she was name on the official "Queen of Pop" list at #8 behind Beyonce, Katy Perry, best friend Taylor Swift, her inspiration Britney Spears and many more. She also beat out Carrie Underwood, Nicki Minaj, Adele, Christina Aguilera, and many more.

Controversies

In December 2007, a brief controversy emerged when photos Cyrus had posted on her private MySpace account, depicting her and a female friend sharing a piece of licorice and "almost kissing", were spread across the internet, prompting rumors of lesbianism. Cyrus comments, "For me, I was like, That's two girls—it's not a big deal. But they got spread around. Like someone copied and pasted and said, Omigod, look at this, and blah blah blah."

In April 2008, several provocative images of Cyrus in her underwear and swimsuit were leaked onto the web by a teenager who hacked Cyrus's Gmail account. Cyrus described the images as "silly, inappropriate shots" and stated, "I am going to make mistakes and I am not perfect. I never intended for any of this to happen and I am truly sorry if I have disappointed anyone." On April 25, 2008, the televised entertainment program Entertainment Tonight reported that Cyrus, then 15, had posed topless for a photoshoot taken by photographer Annie Leibovitz for Vanity Fair. On April 29, 2008, The New York Times clarified that though the pictures left an impression that she was bare-breasted, Cyrus was wrapped in a bedsheet and was actually not topless. Some parents expressed outrage at the nature of the photograph, which a Disney spokesperson described as "a situation [that] was created to deliberately manipulate a 15-year-old in order to sell magazines." Gary Marsh, president of entertainment for Disney Channel Worldwide, was quoted by Portfolio magazine to have said, “For Miley Cyrus to be a 'good girl' is now a business decision for her. Parents have invested in her a godliness. If she violates that trust, she won't get it back." In response to the Internet circulation of the photo and ensuing media attention, Cyrus released a statement of apology on April 27, 2008: "I took part in a photo shoot that was supposed to be 'artistic' and now, seeing the photographs and reading the story, I feel so embarrassed. I never intended for any of this to happen and I apologize to my fans who I care so deeply about." Leibovitz also released a statement: "I'm sorry that my portrait of Miley has been misinterpreted. The photograph is a simple, classic portrait, shot with very little makeup, and I think it is very beautiful."

In May 2008, Gossett, Cyrus's longtime acting agent, left Cunningham Escott Slevin Doherty for United Talent Agency, partially with the hope of "giving Cyrus the major-agency backing that would support a widening career", according to The Hollywood Reporter. About a year later in June 2009, Cyrus left both Gossett and UTA, which had recently negotiated her deals for The Last Song and the fourth season of Hannah Montana, and joined the Creative Artists Agency, which had already represented her for music. Nikki Finke, who broke the news, reported, "Is this fair to UTA? Of course not. But I hear the decision was made by Miley's mother Trish Cyrus".

Cyrus's performance of "Party in the U.S.A." at the 2009 Teen Choice Awards incited a media uproar, with some viewers criticizing Cyrus's provocative outfit and inclusion of a brief pole dance as inappropriate for her age, then sixteen, and for her young fans. Conversely, Newsday reported that her sexualization "has been coming for some time." Ian Drew, senior editor of US Weekly, said, "She already has this risque image, so it really wasn't much of a stretch. That's how Britney [Spears] took off. She was the good girl gone bad, and it looks to be working for Miley as well." Cyrus was also criticized that year for dating Gaston, five years her senior, and for a photo displaying Cyrus and friends making "slant-eyed" expressions, which the Organization of Chinese Americans claimed was offensive to the Asian community. Cyrus apologized for the photo on her website, defending her actions and saying, "In NO way was I making fun of any ethnicity! I was simply making a goofy face."

Later in 2010, TMZ released a video of Cyrus, then 16, giving Adam Shankman, producer of The Last Song, a lap dance at the film's wrap party. Cyrus's father defended her actions, saying Miley was just "having fun" and that "it's what people her age do". Later that year in December, TMZ released a video of Cyrus, which took place five days after her 18th birthday at her Los Angeles home, in which she is seen smoking from a bong. She claimed she was smoking the psychoactive plant salvia divinorum, although this has not been confirmed by anybody but Cyrus herself. Salvia is legal in the state of California, and Cyrus was of legal age at the time the video was shot. Cyrus's father expressed his sadness regarding the matter on Twitter, saying, "Sorry guys. I had no idea. Just saw this stuff for the first time myself. I'm so sad. There is much beyond my control right now".

Filmography

+ Films	! Year	! Title	! Role	Notes
2003	Big Fish	Young Ruthie	Film debut
2007	High School Musical 2	Girl at pool	Cameo
2008	Hannah Montana & Miley Cyrus: Best of Both Worlds Concert		3D Concert film
2008		Penny	Voice-over Role
2009	Hannah Montana: The Movie		Based on TV series
2010		Veronica "Ronnie" Miller	Film adaption of book
2010	Sex and the City 2	Herself	Cameo
2011		Herself	Cameo
2011	So Undercover	Molly	Release: October 28, 2011
2011	LOL: Laughing Out Loud	Lola	Remake of French film
Late 2012	Not Afraid	Katy Harrison	Filming

+ Television	! Year	! Title	! Role	Notes
2001–2003		Kylie	Recurring role
2006–2011	Hannah Montana		Lead role
2006-2008	Disney Channel Games	Herself / Hannah Montana	Contestant, special performer
2006	The Suite Life of Zack & Cody	Miley Stewart / Hannah Montana	"That's So Suite Life of Hannah Montana" (Season 2, Episode 20)
2006–2008	Disney 365	Herself	In 9 episodes, 2006–2008.
2007		Celebrity Star (voice)	"Frog Prince" (Season 2, Episode 5)
2007–2008		Yata (voice)	Recurring role
2008	E! True Hollywood Story	Herself	TV special Documentary
2009		Miley Stewart / Hannah Montana
2011	Saturday Night Live	Herself	Host, March 5 episode.
2011		Herself	Back-to-school special.

Discography

Studio albums

Meet Miley Cyrus (2007)

Breakout (2008)

Can't Be Tamed (2010)

Extended plays

The Time of Our Lives (2009)

Tours

Best of Both Worlds Tour (2007–08)

Wonder World Tour (2009)

Gypsy Heart Tour (2011)

Awards and nominations

List of awards and nominations received by Miley Cyrus

References

Further reading

External links

Miley Cyrus at MTV

}} |- |- |- |- |- |-

Category:1992 births Category:Actors from Tennessee Category:American child actors Category:American child singers Category:American female singers Category:American film actors Category:21st-century actors Category:American pop singers Category:American singer-songwriters Category:American television actors Category:American voice actors Category:Bubblegum pop Category:Fascination Records artists Category:Hollywood Records artists Category:Living people Category:American pop singer-songwriters Category:Child rock musicians Category:Musicians from Tennessee Category:People from Franklin, Tennessee Category:People from Nashville, Tennessee Category:Southern Baptists

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Coordinates	3°8′51″N101°41′36″N
name	Can I Get a Witness
artist	Marvin Gaye
album	Greatest Hits
b-side	"I'm Crazy 'Bout My Baby"
released	September 1963
format	7" single
recorded	July 17, 1963; Hitsville U.S.A.(Detroit, Michigan)
genre	Soul, rock and roll
length	2:53
label	TamlaT 54087
writer	Holland–Dozier–Holland
producer	Brian Holland, Lamont Dozier
last single	"Pride and Joy"(1963)
this single	"Can I Get a Witness"(1963)
next single	"You're a Wonderful One"(1964) }}

"Can I Get a Witness" is a 1963 hit song by Marvin Gaye on the Tamla (Motown) label. Written and produced by Motown songwriting and producing team Holland–Dozier–Holland, the song was built among gospel-styled music and heralded Gaye's beginnings in the church with a rhythm and blues/rock and roll setting. The song featured Gaye on piano, playing a boogie pattern, The Funk Brothers, and members of The Supremes in the background accompanying Gaye. The song became a hit in both the U.S. and the United Kingdom, and British musicians Lulu, Dusty Springfield, The Rolling Stones, Sam Brown and Steampacket (which featured a very young Rod Stewart) recorded cover versions of the song. Gaye's version peaked at number twenty-two on the Pop Singles chart and its title soon became a catchphrase. Lee Michaels' 1971 version reached number thirty-nine on the pop chart; both his and Gaye's versions peaked during Christmas week.

In popular culture

Gaye's recording is featured in the 1999 biographical film The Hurricane.

Personnel

Lead vocals by Marvin Gaye

Background vocals by The Supremes: Diana Ross, Florence Ballard, and Mary Wilson

Instrumentation by The Funk Brothers

Category:1963 singles Category:Marvin Gaye songs Category:Songs written by Holland-Dozier-Holland Category:Motown singles

nn:Can I Get a Witness