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Plasma cosmology

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Plasma cosmology is a nonstandard cosmological model based on the electromagnetic properties of astrophysical plasmas. In this model, the stars and essentially all of the space between them is filled with plasma, electrically conducting gas in which electrons are stripped away from atoms and can move freely. Plasma cosmology attempts to explain the large scale structure and evolution of the universe, from galaxy formation to the cosmic microwave background, in terms of this phase of matter.

Overview

The basic assumptions of plasma cosmology are,

  1. since the universe is nearly all plasma, electromagnetic forces are equal in importance with gravitation.
  2. since we never see effects without causes, we have no reason to assume an origin in time for the universe—an effect without a cause. Thus this approach, in contrast to the currently dominant Big Bang cosmology, does not assume any beginning for the universe.
  3. unlike the Steady state theory, the universe is not changeless. Rather, since every part of the universe we observe is evolving, it assumes that the universe itself is evolving as well.

Plasma cosmology also differs from big bang cosmology methodologically. The plasma approach emphasizes the links between physical processes observable in laboratories on Earth and those that govern the cosmos. It therefore attempts to explain the universe as much as possible in terms of known physics, rather than allowing as, mainstream cosmology does, the introduction of multiple new entities, such as inflation, dark matter and dark energy, which have not been detected in laboratory experiments. Plasma cosmologists, on the other hand, use the theoretical and experimental results of laboratory plasma physics in cosmological applications.

Plasma cosmology was first developed by Swedish physicist Hannes Alfvén together with Oskar Klein, Per Carlqvist and Carl-Gunne Fälthammar. Alfvén was the founder of modern plasma physics, for which he received the Nobel prize. While plasma cosmology has never had the support of a large number of astronomers and physicists, a small group of plasma physicists such as Anthony Peratt and Eric Lerner have continued to develop the approach. As a result the approach now proposes theories for the origin of large scale structures, such as galaxies and cluster and superclusters of galaxies, quasars, the light elements, and the cosmic microwave background. Proponents argue that these theories could explain observations more economically, without introducing the new physics required by the big bang theory. Critics of the theory point out that detailed observational testing of the more mature big bang cosmology has not been rivalled by plasma cosmology.

Alfvén's research

File:Hannes-alfven-stamp.jpg
Hannes Alfvén (1908-1995), made significant advances in the study of plasmas and their application to physics and astronomy

Alfvén's model of plasma cosmology can be divided into two distinct areas.

  1. Cosmic Plasma, his empirical description of the Universe based on the results from laboratory experiments on plasmas
  2. ambiplasma theory, based on a hypothetical matter/antimatter plasma.

Cosmic Plasma

Building on the work of Kristian Birkeland, Alfvén's research on plasma led him to develop the field of magnetohydrodynamics (MHD), a field of work that mathematically models plasma as fluid, and for which he won the Nobel Prize for Physics in 1970. MHD is readily accepted and used by astrophysicists and astronomers to describe many celestial phenomena. However, Alfven pointed out that MHD is an approximation which is accurate only in dense plasmas, like that of stars, where particles collide frequently. It is not valid in the much more dilute plasmas of interstellar and intergalactic space, where electrons and ions circle around the magnetic field lines. Alfven devoted a large section of his Nobel address to attacking this “pseudo plasma” error.

Alfvén felt that many other characteristics of plasmas played a more significant role in cosmic plasmas. These include:

Alfven and his colleagues began to develop plasma cosmology in the 1960’s and 70’s as an extrapolation of their earlier highly successful theories of solar and solar-system phenomena. They pointed out those extremely similar phenomena existed in plasmas at all scales because of inherent scaling laws, ultimately derived from Maxwell's laws. One scale invariant in plasmas is velocity, so that plasmas at scales from the laboratory up to supercluster of galaxies exhibit similar phenomena in a range of velocities from tens to a thousand kilometers per second. In turn this invariance means that the duration of plasma phenomena scales as their size, so that galaxies a hundred thousand light years across with characteristic evolution times of billions of years scale to transient laboratory-scale phenomena lasting a microsecond.

While gravity becomes important at large scales, electromagnetic forces are claimed by plasma cosmology advocates to be rarely negligible and indeed are said to often dominate cosmic processes. Magnetic forces are particularly important since even in neutral plasma (such as almost all astrophysical plasmas) magnetic forces have infinite range, like gravity. For example, in the Local Supercluster of galaxies, the magnetic field is at least 0.3 microgauss over a volume 10 Mpc in radius, so here the magnetic field energy density exceeds the gravitational energy density by at least an order of magnitude.

Alfvén and his collaborators pointed to two plasma phenomena that are crucial in understanding the cosmos. The first is the formation of force-free filaments. When currents move through any plasma, they create magnetic fields which in turn divert currents in such a way that parallel currents attract each other (the pinch effect). Plasma thus naturally become inhomogeneous, with currents and plasmas organizing themselves into force-free filaments, in which the currents move in the same direction as the magnetic field.

Such filaments act to pinch matter together which in turn leads (for large enough filaments) to gravitational instabilities that cause clumps to form along the filaments like beads on a string. These gravitationally-bound clumps, spinning in the magnetic field of the filament, generate electric forces that create a new set of currents moving towards the center of the clump, as in a disk generator. This in turn creates a new set of spiral filaments that set the stage of the coalescence of smaller objects. A hierarchy of superclusters, clusters, galaxies stars and planets is thus formed.

These filaments, as Alfvén and colleagues showed, are critical to the process of gravitational collapse, because they act to transfer angular momentum from the contracting clump. Without such magnetic breaking, the formation of galaxies and stars would be impossible as centrifugal force would prevent contraction. Subsequent to Alfven’s work, the highly magnetized filaments were discovered at several scales in the cosmos, from parsec-scales at the center of the galaxy to supercluster filaments that stretch across hundreds of megaparsecs.

The second phenomenon was the exploding double layer, where charge separation builds up in a current-carrying plasma, leading to the disruption of the current, the generation of high electric fields and the acceleration of energetic particles. This phenomenon, observed in the laboratory, Alfven applied to understand cosmic rays among other phenomena.

Ambiplasma

Alvin and Klein in the early 1960’s pointed out that both physical theory and massive experimental evidence showed that matter and antimatter always come into existence in equal quantities. They developed a theory of cosmic evolution based on the development of an “ambiplasma” consisting of equal quantities of matter and antimatter. Alfven demonstrated that if an ambiplasma was affected by both gravitational and magnetic fields, as could be expected in large-scale regions of space, matter and antimatter would naturally separate from each other. When small matter clouds collided with small antimatter clouds, the annihilation reactions on their border would cause them to repel each other, but matter clouds colliding with matter clouds would merge, leading to increasingly large regions of the universe consisting of almost executively matter or antimatter. Eventually the regions would become so vast that the gamma rays produce by annihilation reactions at their borders would be almost unobservable.

This explanation of the observed dominance of matter in our local part of the universe, relying on well-tested physics laws, contrasted sharply with that proposed by big bang cosmology, which requires an asymmetric production of matter and antimatter at high energy. (If matter and antimatter had been produced in equal quantities in the extremely dense big bang, annihilation would have reduced the universal density to only a few trillionths of that observed.) Such asymmetric matter-antimatter production has never been observed in nature.

Alfven and Klein then went on to use their ambiplasma theory to explain the Hubble relation between redshift and distance. They hypothesized that a very large region of the universe consisting of both matter and antimatter sub-regions, gravitationally collapsed until the matter and antimatter regions were forced together, liberating huge amounts of energy and leading to an expansion of our part of the universe. At no point in this model, however, does the density of our part of the universe become very high.

Unlike Alfven’s other theories, this explanation the Hubble relationship was not upheld by later analysis. Carlqvist determined that there was no way that such a mechanism could lead to the very high redshifts, comparable or greater than unity, that were observed. While Alfven’s separation process was soundly based, it seemed almost impossible for the process to reverse and lead to a re-mixing of matter and antimatter.


Current features and problems for plasma cosmology

Current suporters of plasma cosmology have claimed that the large scale structure of the universe at least superficially appears similar to the structures seen in laboratory plasmas. Since this is only one of the areas of interest to physical cosmology, however, plasma cosmologists have also offered explanations for other features: namely the cosmic microwave background, the redshift distance relationship, and primordial helium abundance.

Microwave background

Even though mainstream interest in plasma cosmology rapidly waned as precise measurements of the cosmic microwave background (CMB), such as those by COBE, both Anthony Peratt and Eric J. Lerner have proposed that plasma cosmology could explain the CMB. In particular, Lerner has shown that plasma cosmology can generate a background by synchrotron radiation. This model fails to predict the CMB anisotropy peaks in the power spectrum or the precise black-body nature of the spectrum. In particular, it fails to predict the 1 degree mode on the sky or the strength of this feature.

Redshifts

Cosmological redshifts are a ubiqitous phenomenon seen that is summarized by the Hubble Law where more distant galaxies have greater redshifts. Advocates of plasma cosmology dispute the claim that this observation indicates an expanding universe and even dispute the more prosaic explanation (used by, for example, the Steady State theory) that they are an indication of recessional velocities. Instead, alternative mechanisms for redshifts are desired.

Although there are many local photon frequency shifting mechanisms observed in laboratory experimentation with plasmas, one problem in using a majority of them to explain cosmological redshifts is that it is difficult to account for a change in the energy of a photon going through plasma without photon scattering (changing the photon's direction of propagation.) In some non-linear optical phenomena, it is argued there may be forms of scattering in which the direction of propagation of the photons is not changed. Specifically, one favorite phenomenon for plasma cosmology advocates is Forward Brillouin Scattering, found locally in laser fusion devices, as an example. This form of forward scattering causes a frequency shift over a range of photon energies and a broadening of spectral lines without changing the direction of propagation of the incident light. However, it does not explain the redshifting of high energy or low energy photons as the conventional explanations do.

Primordial helium abundance

While the Big Bang explains the primordial helium abundance as being due to Big Bang nucleosynthesis, plasma cosmology proponents do not directly explain the ratio of elemental constitutents of the universe. Rather since there is no mechanism for creation of atoms in plasma cosmology, the abundance of light elements is taken to be an initial condition.

Dark matter, dark energy

Advocates of plasma cosmology claim that the observations that are typically seen as evidence for dark matter and dark energy in mainstream cosmology can be explained by plasma processes affecting the dynamics and the redshifts that are associated with these features. It is not clear, however, that evidence from gravitational lensing or from the matter power spectrum or the cosmic microwave background for these features can be explained by plasma processes alone.

Future

Plasma cosmology is not an established scientific theory, and even most advocates agree the explanations provided are much less complete than those of conventional cosmology. Within plasma cosmology, there have been no published papers which make predictions on the primordial helium abundance or which calculate correlation functions.

Figures in plasma cosmology

The following physicists and astronomers helped, either directly or indirectly, to develop this field:

  • Hannes Alfvén - Along with Birkeland, fathered Plasma Cosmology and was a pioneer in laboratory based plasma physics. Received the only Nobel Prize ever awarded to a plasma physicist.
  • Halton Arp - Astronomer famous for his work on anomalous redshifts, "Quasars, Redshifts and Controversies".
  • Kristian Birkeland - First suggested that polar electric currents are connected to a system of filaments (now called "Birkeland Currents") that flowed along geomagnetic field lines into and away from the polar region. Suggested that space is not a vacuum but is instead filled with plasma. Pioneered the technique of "laboratory astrophysics", which became directly responsible for our present understanding of the aurora.
  • Eric Lerner - Claims that the intergalactic medium is a strong absorber of the cosmic microwave background radiation with the absorption occurring in narrow filaments. Postulates that quasars are not related to black holes but are rather produced by a magnetic self-compression process similar to that occurring in the plasma focus.
  • Anthony Peratt - Developed computer simulations of galaxy formation using Birkeland currents along with gravity. Along with Alfven, organized international conferences on Plasma Cosmology.
  • Nikola Tesla - Developed the rotating magnetic field model.
  • Gerrit L. Verschuur - Radio astronomer, writer of "Interstellar matters : essays on curiosity and astronomical discovery" and "Cosmic catastrophes".

See also

Links and resources

Publications

  • IEEE Xplore, IEEE Transactions on Plasma Science, 18 issue 1 (1990), Special Issue on Plasma Cosmology.
  • G. Arcidiacono, "Plasma physics and big-bang cosmology", Hadronic Journal 18, 306-318 (1995).
  • J. E. Brandenburg, "A model cosmology based on gravity-electromagnetism unification", Astrophysics and Space Science 227, 133-144 (1995).
  • J. Kanipe, "The pillars of cosmology: a short history and assessment". Astrophysics and Space Science 227, 109-118 (1995).
  • O. Klein, "Arguments concerning relativity and cosmology," Science 171 (1971), 339.
  • W. C. Kolb, "How can spirals persist?," Astrophysics and Space Science 227, 175-186 (1995).
  • E. J. Lerner, "Intergalactic radio absorption and the Cobe data", Astrophys. Space Sci. 227, 61-81 (1995)
  • E. J. Lerner, "On the problem of Big-bang nucleosynthesis", Astrophys. Space Sci. 227, 145-149 (1995).
  • B. E. Meierovich, "Limiting current in general relativity" Gravitation and Cosmology 3, 29-37 (1997).
  • A. L. Peratt, "Plasma and the universe: Large-scale dynamics, filamentation, and radiation", Astrophys. Space Sci. 227, 97-107 (1995).
  • A. L. Peratt, "Plasma cosmology", IEEE T. Plasma Sci. 18, 1-4 (1990).
  • C. M. Snell and A. L. Peratt, "Rotation velocity and neutral hydrogen distribution dependency on magnetic-field strength in spiral galaxies", Astrophys. Space Sci. 227, 167-173 (1995).

Related Books

  • H. Alfvén, Worlds-antiworlds: antimatter in cosmology, (Freeman, 1966).
  • H. Alfvén, Cosmic Plasma (Reidel, 1981) ISBN 9027711518
  • E. J. Lerner, The Big Bang Never Happened, (Vintage, 1992) ISBN 067974049X
  • A. L. Peratt, Physics of the Plasma Universe, (Springer, 1992) ISBN 0387975756
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