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2 Criticisms of Alfven's model 3 Other work 4 Major figures in plasma cosmology 5 Links and resources 6 Related Books |
Within astrophysics, plasma physics and electromagnetic fields are active areas of research. Many astrophysical bodies are believed to be made of plasma, and within the conventional Big Bang cosmology, the entire early universe consisted of plasma before recombination occurred. Despite the importance of plasma in astrophysics, the standard model of the universe asserts that while electromagnetic forces may be important for describing local phenonmenon, they are not important at large cosmological distances. The reason for this is that unlike the other three forces which are attractive only, electromagnetism is both attractive and repulsive and over large cosmological distances, electromagnetic forces are believed to cancel each other. This is not always the case however, and it can be shown that the electro-magnetic forces are several orders of magnitude greater than the gravitational forces in a plasma.
One of the most well developed models of plasma cosmology which challenges the standard cosmology was first developed in 1965 by Hannes Alfven. In this model, the universe exists as a mixture of matter and antimater which Alfven calls ambiplasma. The cellular regions of matter and antimatter can mutually annhilate, leaving protons and electrons. This may cause a rapid expansion of the region local to the annihilation. The Alfven model deals with the problem of cancellation explained above by postulating that the regions of matter and anti-matter are larger than the presently observable universe.
Alfven's model possesses a number of highly appealing properties. Firstly, it addresses the question of what happened before the Big Bang, which is not addressed by standard Big Bang cosmology. In the Alfven model, the universe has always existed and the expansion we now see merely a phase of a much larger history. Secondly, the model does not invoke any exotic physics, instead modelling the universe using the well-understood electromagnetic forces.
Unfortunately, there are a number of problems with Alfven's model. From a theoretical point of view, Alfven was unable to formalize his model to the point where it is possible to perform numerical simulations similar to those now routinely performed to model the behavior of early galaxies in the standard cosmology and which are used to predict the correlation function of the universe.
Although 3-D formation simulations of single galaxies have been performed using the plasma model (see articles by Anthony Perratt) wherein electromagnetic forces are taken into account along with gravitation, there have been no published papers which attempt to calculate correlation functions and therefore allow detailed comparson with observations.
Another problem is, ironically, that plasma cosmology depends on physics which is, while not completely well-understood, quite well-documented from laboratory experimentation. Because the standard big bang model involves physics that is poorly understood, one can adjust Big Bang models to fit observations by invoking exotic physics, such as the existence of as-yet unobserved particles. It is much harder to modify Alfven's model to fit cosmological observations.
From an observational point of view, the gamma rays emitted by even small amounts of matter/antimatter annihilation should be easily visible using gamma telescopes. However, such gamma rays have not been observed. One could rescue this model by proposing, as Alfven does, that the bubble of matter we are in is larger than the observable universe. This then brings up the question of how one would go about testing the model if the structures that it predicts cannot be observed. In order to test the model, one would have to find some signature of the model in current observations, and this requires that the model be formalized to the point where detailed quantitative predictions can be made. That opens the theoretical problem mentioned in the last paragraph.
It must be remembered that Alfven's model of the universe is not the only model within the field of plasma cosmology. Alfven did play a very large role in founding the fields of plasma physics and plasma cosmology, however many physicists have expounded on his model and there are in fact versions today which greatly account for much of the observable phenomena in the universe, including the CMB, the distribution of galaxies, the formation of galaxies, redshift, etc..
Observations made since the 1960s by Halton Arp claim to disprove the standard model of redshift and Hubble's Law. Arp claims that there are coorelations between quasars and normal galaxies that demonstrate that the cosmic redshift is not due to the expansion of the universe, but is instead local to the source of radiation (example: NGC 7603). Almost all astrophysicists believe that these coorelations do not exist in reality and that Arp's observations are the result of faulty statistics. It is important to note that while these discordant redshifts contradict the Big Bang as a whole, they can still be accounted for in some models of plasma cosmology, although not by Alfven's model which does predict a locally expanding universe. Although there are many local redshifting mechanism observed in laboratory experimentation with fusion plasmas, one problem in using them to explain cosmological redshifts is that it is difficult to change the energy of a photon going through plasma without scattering it. Thus if cosmological redshifts were due to interaction with plasma, one would expect some scattering that would cause distant objects to appear somewhat blurry. This is not observed.
Most astrophysicists believe that the standard Big Bang cosmology makes more detailed and observable predictions than any plasma cosmology model that has been proposed. This include predictions such as the distribution of nuclear elements and the clumpiness of the galaxies. While both are claimed to be accounted for in some manner within plasma cosmology, there have been no published papers which make predictions on the primordial helium abundance or which calculate correlation functions. Hence, as of 2003, there is relatively little interest in the Alfven model or in any other plasma cosmology by the general cosmological community.
The following physicists helped develop this field:
Overview
Criticisms of Alfven's model
Other work
Major figures in plasma cosmology
Links and resources
Related Books