edit In cosmology, dark energy is a hypothetical form of energy which permeates all of space and has strong negative pressure. According to the theory of relativity, the effect of such a negative pressure is qualitatively similar to a force acting in opposition to gravity at large scales. Invoking such an effect is currently the most popular method for explaining the observations of an accelerating universe as well as accounting for a significant portion of the missing mass in the universe. Two prop ...

Including:

• Dark energy - Evidence for dark energy
• Dark energy - Nature of dark energy
• Dark energy - Cosmological constant
• Dark energy - Quintessence
• Dark energy - Other ideas
• Dark energy - Implications for the fate of the universe
• Dark energy - History

Read more here: » Dark energy: Encyclopedia - Dark energy

edit A multiverse (or meta-universe) is the hypothetical set of multiple possible universes, including the observable universe, which comprise the absolute whole of physical reality. The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered. Multiverses have been hypothesized in physics, philosophy; and fiction, particularly in science fiction. (The specific term "multiverse" ...

Including:

• Multiverse - Multiverse hypotheses in physics
• Multiverse - Classification
• Multiverse - Open multiverse
• Multiverse - Bubble Theory
• Multiverse - Big bounce
• Multiverse - Many world interpretation of quantum physics
• Multiverse - M-theory
• Multiverse - String Landscape
• Multiverse - Arguments against multiverse theories
• Multiverse - Multiverse hypotheses in philosophy
• Multiverse - Anthropic principle
• Multiverse - Modal realism
• Multiverse - Trans-world identity issues
• Multiverse - Fictional multiverses

Read more here: » Multiverse: Encyclopedia - Multiverse

All our understanding of the very early universe is very speculative. No accelerator experiments probe sufficiently high energies to provide insight into this period. Scenarios differ radically. Some ideas include the Hartle-Hawking initial state, string landscape, brane inflation, string gas cosmology, and the ekpyrotic universe. Some of these ideas are mutually compatible, others are not. Timeline of the Big Bang - The Planck epoch – 10-43 seconds. See also: Quantum gravit ...

See also:

Timeline of the Big Bang, Timeline of the Big Bang - The very early universe, Timeline of the Big Bang - The Planck epoch – 10^-43 seconds, Timeline of the Big Bang - The Grand Unification Epoch – 10^-33 seconds, Timeline of the Big Bang - Cosmic inflation, Timeline of the Big Bang - The early universe, Timeline of the Big Bang - The electroweak epoch – 10^-12 s, Timeline of the Big Bang - The hadron epoch – 10^-6 s–10^-2 s, Timeline of the Big Bang - Nucleosynthesis – 1 s, Timeline of the Big Bang - Matter domination – 70000 years, Timeline of the Big Bang - Recombination – 500000 years, Timeline of the Big Bang - Dark ages, Timeline of the Big Bang - Structure formation, Timeline of the Big Bang - Reionization, Timeline of the Big Bang - Formation of stars, Timeline of the Big Bang - Formation of galaxies, Timeline of the Big Bang - Formation of groups clusters and superclusters, Timeline of the Big Bang - Formation of the solar system, Timeline of the Big Bang - Today, Timeline of the Big Bang - Ultimate fate of the universe, Timeline of the Big Bang - Heat death, Timeline of the Big Bang - Big crunch, Timeline of the Big Bang - Big rip, Timeline of the Big Bang - Vacuum metastability disaster

Read more here: » Timeline of the Big Bang: Encyclopedia II - Timeline of the Big Bang - The very early universe

There have been a number of non-standard models which have been proposed. Standard responses to some of the claims made in by the variable mass and plasma cosmology proposals are footnoted to the notes section at the end of the article. Non-standard cosmology - Creationist ideas. Main article: Creationist cosmologies Young Earth Creationists who for various reasons object to standard cosmology have offered a variety of alternatives that have ranged from the idea that the universe ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard cosmologies

Brane cosmology assumes that the visible universe lies on a four-dimensional brane which moves in higher dimensional space. Our brane may be one of innumerable others moving through these extra dimensions. The ekpyrotic scenario was proposed by Khoury, Ovrut, Steinhardt and Turok in 2001. It suggests that the visible universe was empty and contracting in the distant past. At some time, our brane collided with another, parallel "hidden" brane, which caused the contracting universe to reverse and begin expanding. Hot matter and radiation was c ...

See also:

Ekpyrotic, Ekpyrotic - Introduction, Ekpyrotic - Outstanding problems, Ekpyrotic - Popular reception

Read more here: » Ekpyrotic: Encyclopedia II - Ekpyrotic - Introduction

There have been a number of non-standard models which have been proposed. Standard responses to some of the claims made in by the variable mass and plasma cosmology proposals are footnoted to the notes section at the end of the article. Non-standard cosmology - Creationist ideas. Young Earth Creationists who for various reasons object to standard cosmology have offered a variety of alternatives that have ranged from the idea that the universe was created as according to Genesis with light from distant obje ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard cosmologies

Multiverse - Classification. According to Max Tegmark, the existence of other universes are a direct implication of cosmological observations. In an article entitled "Parallel Universes" in the May 2003 issue of Scientific American, he presents a clear and comprehensive picture of the idea of parallel universes. Tegmark describes the set of related concepts which share the notion that there are universes beyond the familiar observable one. He goes on t ...

See also:

Multiverse, Multiverse - Multiverse hypotheses in physics, Multiverse - Classification, Multiverse - Open multiverse, Multiverse - Bubble Theory, Multiverse - Big bounce, Multiverse - Many world interpretation of quantum physics, Multiverse - M-theory, Multiverse - String Landscape, Multiverse - Arguments against multiverse theories, Multiverse - Multiverse hypotheses in philosophy, Multiverse - Anthropic principle, Multiverse - Modal realism, Multiverse - Trans-world identity issues, Multiverse - Fictional multiverses

Read more here: » Multiverse: Encyclopedia II - Multiverse - Multiverse hypotheses in physics

The exact nature of this dark energy is a matter of speculation. It is known to be very homogeneous, not very dense and doesn't interact strongly through any of the fundamental forces other than gravity. Since it is not very dense—roughly 10−29 grams per cubic centimeter—it is hard to imagine experiments to detect it in the laboratory (but see the references for a claimed detection). Dark energy can only have such a profound impact on the universe, making up 70% of all energy, because it uniformly fills otherwise empty space. The two leading models are quintessence and the cosmological constant. ...

See also:

Dark energy, Dark energy - Evidence for dark energy, Dark energy - Nature of dark energy, Dark energy - Cosmological constant, Dark energy - Quintessence, Dark energy - Other ideas, Dark energy - Implications for the fate of the universe, Dark energy - History

Read more here: » Dark energy: Encyclopedia II - Dark energy - Nature of dark energy

Structure formation in the big bang model proceeds hierarchically, with smaller structures forming before larger ones. The first structures to form are quasars, which are thought to be bright, early active galaxies and population III stars. Before this epoch, the evolution of the universe could be understood through linear cosmological perturbation theory: that is, all structures could be understood as small deviations from a perfect homogeneous universe. This is computationally relatively easy to study. At this p ...

See also:

Timeline of the Big Bang, Timeline of the Big Bang - The very early universe, Timeline of the Big Bang - The Planck epoch – 10^-43 seconds, Timeline of the Big Bang - The Grand Unification Epoch – 10^-33 seconds, Timeline of the Big Bang - Cosmic inflation, Timeline of the Big Bang - The early universe, Timeline of the Big Bang - The electroweak epoch – 10^-12 s, Timeline of the Big Bang - The hadron epoch – 10^-6 s–10^-2 s, Timeline of the Big Bang - Nucleosynthesis – 1 s, Timeline of the Big Bang - Matter domination – 70000 years, Timeline of the Big Bang - Recombination – 500000 years, Timeline of the Big Bang - Dark ages, Timeline of the Big Bang - Structure formation, Timeline of the Big Bang - Reionization, Timeline of the Big Bang - Formation of stars, Timeline of the Big Bang - Formation of galaxies, Timeline of the Big Bang - Formation of groups clusters and superclusters, Timeline of the Big Bang - Formation of the solar system, Timeline of the Big Bang - Today, Timeline of the Big Bang - Ultimate fate of the universe, Timeline of the Big Bang - Heat death, Timeline of the Big Bang - Big crunch, Timeline of the Big Bang - Big rip, Timeline of the Big Bang - Vacuum metastability disaster

Read more here: » Timeline of the Big Bang: Encyclopedia II - Timeline of the Big Bang - Structure formation

At this time, the universe is filled with a quark-gluon plasma. Timeline of the Big Bang - The electroweak epoch – 10-12 s. See also: Electroweak force In electroweak symmetry breaking, all the fundamental particles are believed to acquire a mass via the Higgs mechanism in which the Higgs boson acquires a vacuum expectation value. At this time, neutrinos decouple and begin travelling freely through space. This cosmic neutrino background, while unlikely to ever be observed in detail, is analogous ...

See also:

Timeline of the Big Bang, Timeline of the Big Bang - The very early universe, Timeline of the Big Bang - The Planck epoch – 10^-43 seconds, Timeline of the Big Bang - The Grand Unification Epoch – 10^-33 seconds, Timeline of the Big Bang - Cosmic inflation, Timeline of the Big Bang - The early universe, Timeline of the Big Bang - The electroweak epoch – 10^-12 s, Timeline of the Big Bang - The hadron epoch – 10^-6 s–10^-2 s, Timeline of the Big Bang - Nucleosynthesis – 1 s, Timeline of the Big Bang - Matter domination – 70000 years, Timeline of the Big Bang - Recombination – 500000 years, Timeline of the Big Bang - Dark ages, Timeline of the Big Bang - Structure formation, Timeline of the Big Bang - Reionization, Timeline of the Big Bang - Formation of stars, Timeline of the Big Bang - Formation of galaxies, Timeline of the Big Bang - Formation of groups clusters and superclusters, Timeline of the Big Bang - Formation of the solar system, Timeline of the Big Bang - Today, Timeline of the Big Bang - Ultimate fate of the universe, Timeline of the Big Bang - Heat death, Timeline of the Big Bang - Big crunch, Timeline of the Big Bang - Big rip, Timeline of the Big Bang - Vacuum metastability disaster

Read more here: » Timeline of the Big Bang: Encyclopedia II - Timeline of the Big Bang - The early universe

During the late 1990s, observations of type Ia supernovae ("one a") suggested that the expansion of the universe is accelerating. These observations have been corroborated by several independent sources since then: the cosmic microwave background, gravitational lensing, large scale structure as well as improved measurements of the supernovae. All these elements are consistent with the concordance Lambda-CDM model. The type Ia supernovae provide the most direct evidence for dark energy. Measuring the velocity of receding objects is acc ...

See also:

Dark energy, Dark energy - Evidence for dark energy, Dark energy - Nature of dark energy, Dark energy - Cosmological constant, Dark energy - Quintessence, Dark energy - Other ideas, Dark energy - Implications for the fate of the universe, Dark energy - History

Read more here: » Dark energy: Encyclopedia II - Dark energy - Evidence for dark energy

Non-standard cosmologies are usually not considered by physicists, because the essentials of the big bang theory have been confirmed by a wide enough range of complementary observations that they believe there is little chance of the theory being replaced in its essentials. A well known letter by advocates of non-standard cosmology has affirmed this: "today, virtually all financial and experimental resources in cosmology are devoted to big bang studies." [ ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard versus standard

One of the major successes of the Big Bang theory has been to provide a prediction that corresponds to the observations of the abundance of light elements in the universe. Along with the explanation provided for the Hubble law and for the Cosmic microwave background, this observation has proved very difficult for alternative theories to explain. Theories which assert that the universe has an infinite age, including many of the theories described above, fail to account for the abundance of deuterium in the cosmos, because deuterium eas ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies

Since the discovery of the cosmic microwave background by Penzias and Robert Wilson in 1965, most cosmologists have concluded that observations are best explained by the big bang model. However, there have been two periods in which interest in non-standard cosmology has increased due to observational data which posed difficulties for the big bang. The first occurred was the late 1970s when there were a number of unsolved problems such as the horizon problem, the flatness problem, and the lack of magnetic monopoles challenged the big bang mod ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Self Creation Cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - History

Cosmologists estimate that the acceleration began roughly 5 billion years ago. Before that, it is thought that the expansion was decelerating, due to the attractive influence of dark matter and baryons. The density of dark matter in an expanding universe disappears more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved but the density of dark energy is nearly u ...

See also:

Dark energy, Dark energy - Evidence for dark energy, Dark energy - Nature of dark energy, Dark energy - Cosmological constant, Dark energy - Quintessence, Dark energy - Other ideas, Dark energy - Implications for the fate of the universe, Dark energy - History

Read more here: » Dark energy: Encyclopedia II - Dark energy - Implications for the fate of the universe

The cosmological constant was first proposed by Einstein as a mechanism to obtain a stable solution of the gravitational field equation that would lead to a static universe, effectively using dark energy to balance gravity. Not only was the mechanism an inelegant example of fine-tuning, it was soon realized that Einstein's static universe would actually be unstable because local inhomogeneities would ultimately lead to either the runaway expansion or contraction of the universe. The equilibrium is unstable: if the universe expands slightly, ...

See also:

Dark energy, Dark energy - Evidence for dark energy, Dark energy - Nature of dark energy, Dark energy - Cosmological constant, Dark energy - Quintessence, Dark energy - Other ideas, Dark energy - Implications for the fate of the universe, Dark energy - History

Read more here: » Dark energy: Encyclopedia II - Dark energy - History

There are major outstanding problems with the ekpyrotic scenario. Foremost among them is that colliding branes are not understood by string theorists, and nobody knows if the scale invariant spectrum will be destroyed by the big crunch, or even what happens when two branes collide. Moreover, like cosmic inflation, while the general character of the forces (in the ekpyrotic scenario, a force between branes) required to create the vacuum fluctuations is known, there is no candidate from particle physics. Moreover, the scenario uses some essent ...

See also:

Ekpyrotic, Ekpyrotic - Introduction, Ekpyrotic - Outstanding problems, Ekpyrotic - Popular reception

Read more here: » Ekpyrotic: Encyclopedia II - Ekpyrotic - Outstanding problems

It's not science. Critics claim that there is a lack of empirical correlation and testability in these theories and thus they are without hard physical evidence and must therefore be considered unfalsifiable, currently outside the methodology of scientific investigation to confirm or disprove, and therefore more mathematically theoretical and metaphysical than scientific in nature. But Tegmark points out, improved measurements of the microwave background radiation and of the large-scale distribution of matter may fortify or knock down two pillars of the mult ...

See also:

Multiverse, Multiverse - Multiverse hypotheses in physics, Multiverse - Classification, Multiverse - Open multiverse, Multiverse - Bubble Theory, Multiverse - Big bounce, Multiverse - Many world interpretation of quantum physics, Multiverse - M-theory, Multiverse - String Landscape, Multiverse - Arguments against multiverse theories, Multiverse - Multiverse hypotheses in philosophy, Multiverse - Anthropic principle, Multiverse - Modal realism, Multiverse - Trans-world identity issues, Multiverse - Fictional multiverses

Read more here: » Multiverse: Encyclopedia II - Multiverse - Arguments against multiverse theories

Non-standard cosmologies are usually not considered by physicists, because the essentials of the big bang theory have been confirmed by a wide enough range of complementary observations that they believe there is little chance of the theory being replaced in its essentials. A well known letter by advocates of non-standard cosmology has affirmed this: "today, virtually all financial and experimental resources in cosmology are devoted to big bang studies." [ ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard versus standard

Since the discovery of the cosmic microwave background by Penzias and Robert Wilson in 1965, most cosmologists have concluded that observations are best explained by the big bang model. However, there have been two periods in which interest in non-standard cosmology has increased due to observational data which posed difficulties for the big bang. The first occurred was the late 1970s when there were a number of unsolved problems such as the horizon problem, the flatness problem, and the lack of magnetic monopoles challenged the big bang mod ...

See also:

Non-standard cosmology, Non-standard cosmology - Non-standard versus standard, Non-standard cosmology - History, Non-standard cosmology - Non-standard cosmologies, Non-standard cosmology - Creationist ideas, Non-standard cosmology - Quasi-steady state, Non-standard cosmology - Tired light, Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts, Non-standard cosmology - Plasma cosmology, Non-standard cosmology - Nucleosynthesis objections to non-standard cosmologies, Non-standard cosmology - Notes, Non-standard cosmology - Bibliography

Read more here: » Non-standard cosmology: Encyclopedia II - Non-standard cosmology - History