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Lettris is a curious tetris-clone game where all the bricks have the same square shape but different content. Each square carries a letter. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares.
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Plasma cosmology is a term describing a loose set of non-standard ideas about cosmology. Its central idea is that the dynamics of ionized gases (or plasmas) plays a decisive role in the physics of the universe at scales larger than the Solar system. Today, almost all cosmologists and astronomers are dismissive of the idea. The current consensus of astrophysicists is instead that Einstein's theory of general relativity, a theory of gravity, explains the origin and evolution of the universe on cosmic scales.
Some of the ideas of plasma cosmology are attributed to the 1970 Nobel laureate Hannes Alfvén. Alfvén proposed the use of plasma scaling to extrapolate the results of laboratory and space plasma physics experiments to scales orders-of-magnitude greater (see box). While it is widely agreed that plasma physics is essential to many astrophysical phenomena in the early universe and is still important today to phenomena up to the scale of the Solar system, plasma cosmology continues this extrapolation to the universe on the largest observable scales.
The term plasma universe is sometimes used as a synonym for plasma cosmology and sometimes plasma cosmology is seen as the evolution of the plasma universe. Plasma cosmology researchers explicitly distance themselves from the methodology and some of the ideas of the electric universe. Some of the ideas of the electric universe are based on the theories and discoveries of plasma cosmologists, but other ideas are not.
In contrast to plasma cosmology, plasma physics is accepted uncontroversially as having great influence on many astrophysical phenomena. The majority of ordinary matter in the universe is in the form of plasma, and plasma is a good conductor of electricity. An important figure in this field was Hannes Alfvén, who devoted much of his professional career to investigating plasmas and was awarded the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics (MHD).
Alfvén's view was that plasma played an important role in the universe. He asserted that electromagnetic forces are far more important than gravity when acting on interplanetary and interstellar charged particles. The first step of Alfvén's 'cosmic triple jump' was to scale plasma theory from the laboratory to the magnetosphere. Alfvén wrote a paper in 1939 supporting the theory of Kristian Birkeland, who had written in 1913 that what is now called the Solar wind generated currents in space that caused the aurora. Birkeland's theory was disputed at the time and Alfvén's work in turn was disputed for many years by the British geophysicist and mathematician Sydney Chapman, a senior figure in space physics, who argued the mainstream view that currents could not cross the vacuum of space and therefore the currents had to be generated by the Earth. But eventually in 1967 Birkeland's then fringe theory was proved to be correct after a probe was sent into space, and these magnetic field aligned currents are now named Birkeland currents in his honour. The crucial results were obtained from U.S. Navy satellite 1963-38C, launched in 1963 and carrying a magnetometer above the ionosphere.
Plasma effects being vital in slowing down a protostar's spin in stellar formation is accepted as mainstream science today (although the actual mechanism is not so clearcut). One proposed mechanism to remove angular momentum and allow a protostar to contract is magnetic braking. Other things in the Solar System that are beyond the Earth's magnetosphere in which plasma plays a central role are the heliospheric current sheet and the interplanetary medium. Theories in astrophysical plasma in the Solar system are a fundamental part of plasma cosmology, it is the second step in Alfvén's 'cosmic triple jump'.
On a larger scale, galaxy groups and clusters have a lower plasma density by several orders of magnitude, and magnetic fields are not strong enough to significantly affect virializing processes. Standard astrophysical structure formation models, at the level of galaxy formation, depend on the mass distribution of the simulated system rather than its electrodynamic interactions. Such models do however have to assume the existence of dark matter to account for observed galaxy rotation curves. Plasma cosmologists propose that plasma effects explain galaxy rotation curves without the need for dark matter.
Alfvén hypothesized that Birkeland currents (here meaning currents in space plasmas which are aligned with magnetic field lines) were responsible for many filamentary structures and that a galactic magnetic field and associated current sheet, with an estimated galactic current of 1017 to 1019 amperes, might promote the contraction of interstellar clouds and may even constitute the main mechanism for contraction, initiating star formation. This is in opposition to the standard view that magnetic fields can hinder collapse. However large-scale Birkeland currents have not been observed and the length scale for charge neutrality is predicted to be far smaller than the relevant cosmological scales.
Plasma cosmology theory was being worked on in the 1960s by Alfvén, Oskar Klein and Carl-Gunne Fälthammar, and of particular importance was Alfvén's 1966 book Worlds-Antiworlds. During 1971, Klein extended Alfvén's Worlds-Antiworlds proposals and developed the "Alfvén-Klein model" of the universe, or meta-galaxy as they called it at the time (see the Shapley-Curtis debate for more on the history of distinguishing between the universe and the Milky Way galaxy). In this Alfvén-Klein cosmology (sometimes called Klein-Alfvén cosmology), the universe is made up of equal amounts of matter and antimatter with the boundaries between the regions of matter and antimatter being delineated by cosmic electromagnetic fields formed by double layers, thin regions comprising two parallel layers with opposite electrical charge. These boundary regions would be made up of matter and antimatter that would generate annihilation radiation, forming a plasma. Alfvén introduced the term ambiplasma for a plasma made up of matter and antimatter and the double layers are thus formed of ambiplasma. According to Alfvén, such an ambiplasma would be relatively long-lived as the component particles and antiparticles would be too hot and too low-density to annihilate each other rapidly. The double layers will act to repel clouds of opposite type, but combine clouds of the same type, creating ever-larger regions of matter and antimatter. The idea of ambiplasma was developed further into the forms of heavy ambiplasma (protons-antiprotons) and light ambiplasma (electrons-positrons).
Alfvén-Klein cosmology was proposed in part to explain the observed baryon asymmetry in the universe, starting from an initial condition of exact symmetry between matter and antimatter. According to Alfvén and Klein, ambiplasma would naturally form pockets of matter and pockets of antimatter that would expand outwards as annihilation between matter and antimatter occurred in the double layer at the boundaries. They concluded that we must just happen to live in one of the pockets that was mostly baryons rather than antibaryons, explaining the baryon asymmetry. The pockets, or bubbles, of matter or antimatter would expand because of annihilations at the boundaries, which Alfvén considered as a possible explanation for the observed apparent expansion of the universe, which would be merely a local phase of a much larger history. Alfvén postulated that the universe has always existed due to causality arguments and the rejection of ex nihilo models, such as the Big Bang, as a stealth form of creationism. The exploding double layer was also suggested by Alfvén as a possible mechanism for the generation of cosmic rays, x-ray bursts and gamma-ray bursts.
In 1993, theoretical cosmologist Jim Peebles criticized the cosmology of Klein (1971) and Alfvén's 1966 book, Worlds-Antiworlds, writing that "there is no way that the results can be consistent with the isotropy of the cosmic microwave background radiation and X-ray backgrounds". In his book he also claimed that Alfvén's models do not predict Hubble's law, the abundance of light elements, or the existence of the cosmic microwave background.
Laboratory experiments done in the 1950s by Winston H. Bostick which involved vapourising titanium wires with a 10,000 A current, turning them into a plasma, showed plasma shapes which mimicked the shape of real galaxies. Bostick claimed these experiments showed how galaxies had initially formed from plasma under the influence of a magnetic field.
Computer simulations in the 1980s showing the cross-section of two plasma filaments coalescing also mimicked the shape of real galaxies. Simulations of colliding plasma clouds by Anthony Peratt, starting 300,000 light years apart in filaments with currents of 1018 Amps, showed many similarities with observations of galaxies. This is a more complicated 3D version of two plasma filaments joining. Basically, the clouds begin to spin and are distorted (because of the same offset forces as in the case of the filaments joining) into two arms, separated at the centre by a buffer region (which corresponds to the gap between the filaments in the case of two filaments joining). The simulations also showed central radio sources of synchrotron radiation and emerging jets of material from the central buffer region, which looked like that observed from quasars and active galactic nuclei, without the need for supermassive black holes required in simulations based on gravity alone. Extending the simulation run time showed "the transition of double radio galaxies to radioquasars to radioquiet QSO's to peculiar and Seyfert galaxies, finally ending in spiral galaxies". The simulation accounted for the spin of galaxies (they gain spin at the expense of the magnetic fields), and also accounted for flat galaxy rotation curves without dark matter (the discrepancy between observed galaxy rotation curves and those simulated based on gravity alone had to be accounted for by introducing dark matter). With magnetic fields in play, the spiral arms of galaxies are like rolling springs that have the same rotational velocity along their length (i.e. a spiral arm shows what would happen to a hypothetical radial spoke after some considerable time), creating in simulations flat galaxy rotation curves in spiral galaxies as observed in nature.
Complementing and in agreement with these simulation studies by Peratt was an analytical model of a plasma quasar mechanism by Lerner. This contradicts the standard model of quasars as being powered by supermassive black holes which are illuminated by radiation from the luminous matter they are accreting. A device based on this mechanism to concentrate power is called a dense plasma focus (DPF) device and is potentially useful for controlled nuclear fusion on Earth. Lerner has gone on to research these devices and in March 2012 his team announced their DPF device had achieved temperatures of 1.8 billion degrees, beating the old record of 1.1 billion that had survived since 1978.
Experimentally plasma filaments are typically 10,000 times longer than they are wide. Thus to form galaxies, the filaments would be 100,000 light years across and one billion light years long, and such filaments would form the large-scale structure of the universe such as the Great Wall: 500 million light-years long, 300 million light-years wide and 15 million light-years thick. Prior to the discovery of the Great Wall in 1989 the mainstream consensus was that at these scales the universe would be uniform, but plasma cosmology had predicted the scale of these structures years before then (see e.g.).
In 2006 it was discovered that "spiral galaxies, like the Milky Way, line up like beads on a string, with their spin axes aligned with the filaments that outline voids". It is unclear what this means for theories of galaxy formation.
While plasma cosmology has never had the support of most astronomers or physicists, a few researchers have continued to promote and develop the approach, publishing mostly in the IEEE journal Transactions on Plasma Science. Additionally, in 1991, Eric J. Lerner, an independent researcher in plasma physics and nuclear fusion, wrote a popular-level book supporting plasma cosmology titled The Big Bang Never Happened.
Proponents of plasma cosmology claim electrodynamics is as important as gravity in explaining the structure of the universe, and speculate that it provides an alternative explanation for the evolution of galaxies and the initial collapse of interstellar clouds. In particular plasma cosmology is claimed to provide an alternative explanation for the flat rotation curves of spiral galaxies and to do away with the need for dark matter in galaxies and with the need for supermassive black holes in galaxy centres to power quasars and active galactic nuclei. This is controversial, as theoretical analysis shows that "many scenarios for the generation of seed magnetic fields, which rely on the survival and sustainability of currents at early times [of the universe are disfavored]", i.e. Birkeland currents of the magnitude needed (say 1018 Amps) for galaxy formation are not thought to exist.
Light element production without Big Bang nucleosynthesis (as required in e.g. Alfvén-Klein cosmology) has been discussed in the mainstream literature and was determined to produce excessive x-rays and gamma rays beyond that observed. This issue has not been completely addressed by plasma cosmology proponents in their proposals.
In 1995 Eric Lerner published the only proposal based on plasma cosmology to explain the cosmic microwave background radiation (CMB) since the Cosmic Background Explorer (COBE) results were announced in 1992. He argues that his model can explain both the fidelity of the CMB spectrum to that of a black body and the low level of anisotropies found. The sensitivity and resolution of the measurement of the CMB anisotropies was greatly advanced by WMAP. The fact that the CMB is so isotropic, in line with the predictions of the Big Bang model, was subsequently heralded as a major confirmation of the Big Bang model to the detriment of alternatives. These measurements show the acoustic peaks in the early universe are fit with high accuracy by the predictions of the Big Bang model. There has never been an attempt to explain the detailed spectrum of the anisotropies within the framework of plasma cosmology.