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Photon Epoch
In physical cosmology, the photon epoch was the period in the evolution of the early universe in which photons dominated the energy of the universe. The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang. Atomic nuclei were created in the process of , which occurred during the first few minutes of the photon epoch. For the remainder of the photon epoch, the universe contained a hot dense plasma of nuclei, electrons and photons. At the start of this peri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Death
Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock, the destruction of equipment by overheating *A Supernova, heat death of a star, along with the death of the star itself In arts *''The Heat Death of the Universe'', 2003 album by punk band Off Minor *"The Heat Death of the Universe", a short story by Pamela Zoline See also * Dead Heat (other) A dead heat is a rare situation in various racing sports in which the performances of competitors are judged to be so close that no difference between them can be resolved. The result is declared a tie and the competitors are awarded a joint r ... * Heat Death of the Universe (other) * {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deuterium
Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more common H has no neutrons. The name ''deuterium'' comes from Greek '' deuteros'', meaning "second". American chemist Harold Urey discovered deuterium in 1931. Urey and others produced samples of heavy water in which the H had been highly concentrated. The discovery of deuterium won Urey a Nobel Prize in 1934. Nearly all deuterium found in nature was synthesized in the Big Bang 13.8 billion years ago, forming the primordial ratio of H to H (~26 deuterium nuclei per 10 hydrogen nuclei). Deuterium is subsequently produced by the slow stellar proton–proton chain, but rapidly destroyed by exothermic fusion reactions. The deuterium–deuterium reaction has the second-lowest energy threshold, and is the most astrophysically acce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Big Bang Nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis (also known as primordial nucleosynthesis, and abbreviated as BBN) is a model for the production of light nuclei, deuterium, 3He, 4He, 7Li, between 0.01s and 200s in the lifetime of the universe. The model uses a combination of thermodynamic arguments and results from equations for the expansion of the universe to define a changing temperature and density, then analyzes the rates of nuclear reactions at these temperatures and densities to predict the nuclear abundance ratios. Refined models agree very well with observations with the exception of the abundance of 7Li. The model is one of the key concepts in standard cosmology. Elements heavier than lithium are thought to have been created later in the life of the Universe by stellar nucleosynthesis, through the formation, evolution and death of stars. Characteristics The Big Bang nucleosynthesis (BBN) model assumes a homogeneous plasma, at a temperature corresponding to 1 MeV, co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timeline Of The Early Universe
The timeline of the universe begins with the Big Bang, 13.799 ± 0.021 billion years ago, and follows the formation and subsequent evolution of the Universe up to the present day. Each ''era'' or ''age'' of the universe begins with an "epoch", a time of significant change. Times on this list are relative to the moment of the Big Bang. First 20 minutes Planck epoch * c. 0 seconds (13.799 ± 0.021 Gya): Planck epoch begins: Big Bang occurs in which ordinary space and time develop out of a primeval state described by a quantum theory of gravity or "theory of everything". All matter and energy of the universe is contained in a hot, dense point (gravitational singularity) Grand unification epoch * c. 10−43 seconds: Gravity separates and begins operating on the universe—the remaining fundamental forces stabilize into the electronuclear force, also known as the Grand Unified Force or Grand Unified Theory (GUT), mediated by (the hypothetical) X and Y bosons which allo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observable Universe
The observable universe is a Ball (mathematics), spherical region of the universe consisting of all matter that can be observation, observed from Earth; the electromagnetic radiation from these astronomical object, objects has had time to reach the Solar System and Earth since the beginning of the metric expansion of space, cosmological expansion. Assuming the universe is isotropy, isotropic, the distance to the edge of the observable universe is equidistant, the same in every direction. That is, the observable universe is a sphere, spherical region centered on the observer. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth. The word ''observable'' in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the speed of light itself. No signal can travel faster ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Of Last Scattering
The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost uniform and is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the electromagnetic spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Allan Penzias and Robert Woodrow Wilson was the culmination of work initiated in the 1940s. The CMB is landmark evidence of the Big Bang theory for the origin of the universe. In the Big Bang cosmological models, during the earliest periods, the universe was filled with an opaque fog of dense, hot plasma of sub-atomic particles. As the universe expanded, this plasma cooled to the point where protons and electro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structure Formation
In physical cosmology, structure formation describes the creation of galaxies, galaxy clusters, and larger structures starting from small fluctuations in mass density resulting from processes that created matter. The universe, as is now known from observations of the cosmic microwave background radiation, began in a hot, dense, nearly uniform state approximately 13.8 billion years ago. However, looking at the night sky today, structures on all scales can be seen, from stars and planets to galaxies. On even larger scales, galaxy clusters and sheet-like structures of galaxies are separated by enormous voids containing few galaxies. Structure formation models gravitational instability of small ripples in mass density to predict these shapes, confirming the consistency of the physical model. The modern Lambda-CDM model is successful at predicting the observed large-scale distribution of galaxies, clusters and voids; but on the scale of individual galaxies there are many complicatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Microwave Background Radiation
The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost isotropic, uniform and is not associated with any star, galaxy, or other astronomical object, object. This glow is strongest in the microwave region of the electromagnetic spectrum. The accidental Discovery of cosmic microwave background radiation, discovery of the CMB in 1965 by American radio astronomers Arno Allan Penzias and Robert Woodrow Wilson was the culmination of work initiated in the 1940s. The CMB is landmark evidence of the Big Bang scientific theory, theory for the origin of the universe. In the Big Bang cosmological models, during the earliest periods, the universe was filled with an Opacity (optics), opaque fog of dense, hot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photodissociation
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons with one target molecule that dissociates into two fragments. Here, “light” is broadly defined as radiation spanning the vacuum ultraviolet (VUV), ultraviolet (UV), visible, and infrared (IR) regions of the electromagnetic spectrum. To break covalent bonds, photon energies corresponding to visible, UV, or VUV light are typically required, whereas IR photons may be sufficiently energetic to detach ligands from coordination complexes or to fragment supramolecular complexes. Photolysis in photosynthesis Photolysis is part of the light-dependent reaction, light phase, photochemical phase, or Hill reaction of photosynthesis. The general reaction of photosynthetic photolysis can be given in terms of photons as: :\ce + 2 \text \longrigh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Death Of The Universe
The heat death of the universe (also known as the Big Chill or Big Freeze) is a scientific hypothesis regarding the ultimate fate of the universe which posits the universe will evolve to a state of no thermodynamic free energy and, having reached maximum entropy, will therefore be unable to sustain any further thermodynamic processes. The hypothesized heat death does not imply any particular absolute temperature; it only requires that temperature differences or other processes may no longer be exploited to perform work. In the language of physics, this is when the universe reaches thermodynamic equilibrium. If the curvature of the universe is hyperbolic or flat, or if dark energy is a positive cosmological constant, the universe will continue expanding forever, and a heat death is expected to occur, with the universe cooling to approach equilibrium at a very low temperature after a long time period. The theory of heat death stems from the ideas of Lord Kelvin who, in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasma (physics)
Plasma () is a state of matter characterized by the presence of a significant portion of charged particles in any combination of ions or electrons. It is the most abundant form of ordinary matter in the universe, mostly in stars (including the Sun), but also dominating the rarefied intracluster medium and Outer space#Intergalactic space, intergalactic medium. Plasma can be artificially generated, for example, by heating a neutral gas or subjecting it to a strong electromagnetic field. The presence of charged particles makes plasma electrically conductive, with the dynamics of individual particles and macroscopic plasma motion governed by collective electromagnetic fields and very sensitive to externally applied fields. The response of plasma to electromagnetic fields is used in many modern devices and technologies, such as plasma display, plasma televisions or plasma etching. Depending on temperature and density, a certain number of neutral particles may also be present, in wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
