Non-standard cosmology

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A non-standard cosmology is a cosmological idea that contradicts the standard model of cosmology. This contrasts to cosmological models which don't match the standard Lambda-CDM model, but work within the framework of the Big Bang or only aim to supplement the Big Bang model with a first cause, like the Ekpyrotic model.

Contents

History

The non-standard cosmology term has been used since the late 1960s after the discovery of the cosmic microwave background radiation (CMB) in 1965 by Penzias and Wilson. These observations, combined with the theory of big bang nucleosynthesis and other evidence which suggested that the universe evolved, caused most cosmologists to favor the Big Bang theory over the steady state theory. Since around this time, a non-standard cosmology has primarily meant any description of cosmology which questions the fundamental propositions of the Big Bang. Today, non-standard cosmologies are promoted by a few generally independent researchers and amateurs who disagree with foundational assumptions and so reject the idea of applying concordance criteria to their models. For this reason there is not a single non-standard cosmology. Within the category are many different models which often contradict each other.

Although most astronomers since the 1960s have concluded that observations are best explained by a variation of the big bang model, there have been two periods in which interest in non-standard cosmology increased due to observational data which posed difficulties for the big bang. The first occurred in 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 which challenged the models of the big bang then under consideration. These issues were eventually resolved by cosmic inflation in the 1980s which subsequently became part of all standard cosmologies from then on. The second occurred in the mid-1990s when observations of the ages of globular clusters and the primordial helium abundance showed the potential of seriously challenging the big bang. However, by the late 1990s, most astronomers had concluded that these observations did not challenge the big bang and additional data from COBE and WMAP provided detailed quantitative measures which were consistent with standard cosmologies.

In an Open Letter to the Scientific Community, signed by thirty-three non-standard cosmology supporters, including astronomer Hermann Bondi, and published in the May 22nd 2004 issue of the New Scientist periodical, they protest that the Big Bang theory has not been able to provide a basis for quantitative predictions. They also decry the lack of funding for the support of non-standard research.

In contrast to this, most astrophysicists consider the Big Bang theory, in it current state as Lambda-CDM model, hugely successful. Also the 1990s gave a order of magnitude improvement to the precision of observational data, which continued to agree with the standard cosmology.

In addition, most cosmologists react very strongly against charges that non-standard cosmologies are being suppressed for ideological reasons and point out that developing a theoretical model of non-standard cosmology requires no particularly large amount of funding. While observational cosmology does require a great deal of funding and telescope time, the major observational cosmology projects, such as COBE, WMAP, and the massive galaxy surveys, do not assume the correctness of standard cosmologies.

Non-standard Cosmologies

There have been a number of non-standard models which have been proposed.

Creationist ideas

Main article: Young Earth 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 was created as according to Genesis with light from distant objects created in transit to more involved critiques such as proposing a non-constant speed of light or a bounded universe that erupted from a white hole. Old Earth creationists do not object to the standard model of cosmology in astrophysics and are known to debate their fellow creationists over the issue.

Quasi Steady State

Although the original steady state model is now considered to be contrary to observations even by its originators, a modification of the steady state model has been proposed which envisions the universe as originating through many little bangs rather than one big bang. It supposes that the Universe goes through periodic expansion and contraction phases, with a soft "rebound" in place of the Big Bang. Thus the redshift is explained by the fact that the Universe is currently in an expansion phase.

The steady state and quasi-steady state theorists have proposed that the intergalactic medium contains microscopic iron dust particles or whiskers, which can scatter radio waves in such a manner as to produce an isotropic CMB. However, there is no observational evidence for the existence of these iron particles.

Tired Light

The tired light effect was proposed by Fritz Zwicky in 1929 to explain the observed cosmological redshift. It has been found incompatible with the observed time dilation that is associated with the cosmological redshift.

A traditional explanation of this effect is dynamical friction of photons; the photons' gravitational interactions with stars and other material will progressively reduce their momentum, thus producing a redshift. However, this process will also tend to blur images of distant objects, and no such blurring has been detected [1] (http://www.astro.ucla.edu/~wright/tiredlit.htm).

Note that in the General Theory of Relativity, dynamical friction does not apply to photons (basically, because photons are massless). This does not contradict the conservation laws, because in the general theory they apply only locally, and dynamical friction is inherently non-local.

Variable Mass Hypothesis and Intrinsic Redshifts

There remain small numbers of astrophysicists, including Jay Narlikar, Y.P. Varshni and Halton Arp, who argue that redshifts in galaxies do not correlate with distance and/or are not due to the Doppler effect, and that this invalidates the need for the Big Bang.

Halton Arp, one of the most famous of these astrophysicists, bases his alternative theory on observations made by himself and his team from as far back as 1960. The controversy is an amalgamated holdover from the history of quasar observations and steady state theories. Before the redshifts of the objects were determined, Arp argued that the Eddington luminosity set limits on how distant the quasars could be. Because he was also a detractor of the Big Bang, Arp used his observational skills to try to refute the expansion of the universe. When most other scientists accepted the inability of alternatives to explain the observations that the Big Bang explained, Arp kept to his guns. From the 1970s onward, Arp has made observations of correlations between quasars (and more recently, X-ray sources from Chandra data) and (relatively) nearby AGN (Active Galactic Nuclei) which he claims demonstrates that quasar redshifts are not entirely due to the expansion of the universe, but contain a local, or non-cosmological, component. Arp claims that clusters of quasars have been observed around many galaxies which all have some properties in common:

  • The active galaxy always has a lower redshift than any of its associated quasars.1
  • The quasars tend to lie within a narrow conical zone centered about the minor (rotational) axis of the associated active galaxy.2
  • Schematically, the quasars' redshifts are inversely proportional to their angular distances from the AGN, i.e. as apparent distance from the AGN increases, the redshift of the quasars decrease.3
  • Some of the quasars occur as pairs on either side of an AGN, particularly the X-ray sources appearing in the Chandra data.

These observations indicate to Arp that a relationship may exist between quasars (or at least a certain type of quasar) and AGN that is completely unrelated to the standard explanation that quasars are AGN at cosmological distances.4 Arp claims that certain quasars originate as very high redshift objects ejected from the nuclei of active galaxies, and gradually lose their non-cosmological redshift component as they evolve into galaxies.5 This stands in stark contradiction to most accepted models of galaxy formation.

The biggest problem with Arp's analysis is that today there are tens of thousands of quasars with known redshifts discovered by various sky surveys. The vast majority of these quasars are not correlated in any way with nearby AGN. Indeed, with improved observing techniques, a number of host galaxies have been observed around quasars which indicates that those quasars at least really are at cosmological distances and are not the kind of objects Arp proposes. Arp's analysis, according to most scientists, suffers from being based on small number statistics and hunting for peculiar coincidences and odd associations. In a vast universe such as our own, peculiarities and oddities are bound to appear if one looks in enough places. Unbiased samples of sources, taken from numerous galaxy surveys of the sky show none of the proposed 'irregularities' nor any statistically significant correlations that Arp suggests exist.

In addition, it is not clear what mechanism would be responsible for such high initial redshifts, or indeed its gradual dissipation over time as the quasar evolves. It is also unclear why objects ejected from a galaxy should never seem to produce a blue shift. Moreover it is unclear how nearby quasars would explain some features in the spectrum of quasars which the standard model easily explains. In the standard cosmology, the clouds of neutral hydrogen between the quasar and the earth at different red shifts spikes between the quasar redshift and the rest frequency of Lyman alpha in a feature known as the Lyman-alpha forest. Moreover, in extreme quasars one can observe the absorbion of neutral hydrogen which has not yet been reionized in a feature known as the Gunn-Peterson trough. Most cosmologists see this missing theoretical work as sufficient reason to explain the observations as either chance or error.

Halton Arp attributes his observations to the "variable-mass hypothesis", which has its foundations within the frame of Machian physics. The variable-mass theory invokes constant matter creation from active galactic nuclei, which puts it into the class of steady-state theory.

A consequence of Arp's proposed AGN-origin of quasars would be that quasars would be much closer, much larger, and much less luminous than currently supposed and their heavy element composition would no longer require primaeval Population III stars. Such a theory would predict that the heavy element composition of quasars would be similar to the associated AGN, though observed metal lines in quasars are notoriously weaker than AGN. Variable luminosity and absorption phenomena such as the Lyman-alpha forest would both be explained by as yet theoretically undeveloped "local means".

Plasma Cosmology

Plasma cosmology is a classic non-standard model which was invented by Hannes Alfven to account for cosmological observations. It was developed, in part, as an alternative to the steady state theory as well as the Big Bang. Plasma cosmology has much in common with the steady state theory. In particular, both include the Strong Cosmological Principle which includes an assumption that the universe is isotropic in time as well as in space. One difference between plasma cosmology and steady-state is that plasma cosmology does not invoke matter creation; rather it hypothesises a flow of matter between different areas of the universe. In some versions of plasma cosmology, matter is explicitly assumed to have always existed, or at least that it formed at a time so far in the past as to be forever beyond our empirical methods of investigation.

Some plasma cosmologists account for the observed galaxy rotation curves by supposing the existence of additional electro-magnetic forces and interactions.6 They claim that by treating the arms of galaxies as plasma filaments interacting with electromagnetic fields, the filamentary structure of galaxy clusters and superclusters can be viewed as a result of the self-amplifying nature of currents in plasmas.7 In this way, plasma cosmology proports to explain two observations often attributed in the standard cosmological models as due to dark matter. However, proponents of the Big Bang theory claim that no non-standard cosmology explains in detail the totality of proposed evidence for dark matter.

Alfven, Lerner and others working within plasma cosmology have claimed that the temperature, isotropy, and non-polarisation of the CMB can be readily explained as the diffusion of galactic radio emission by the magnetic fields of intervening plasma filaments. Electrons travelling along the large, weak magnetic field lines of a galaxy can absorb radio, and re-emit it in a different direction. This scatters the radiation, much as light from the sun is scattered in a dense fog. This can also explain the observed decrease in radio brightness of galaxies relative to their IR luminosity with increasing redshift. Lerner explains that radiation from distant galaxies successively interacts with the magnetic fields of many intervening galaxies, nebulae, supernova remnants and so on, resulting in an isotropic scatter.8 However, standard cosmologists have been able to model in detail not only these global features, but also the detailed measurements of anisotropies and polarization of the CMB, and have identified a number of features such as peaks and valleys in its power spectrum which correspond to cosmological quantities.

With regards to anisotropy studies, the WMAP experiment has been especially fruitful in providing a goldmine of data that is interpreted easily by the standard cosmological models. The inability thus far of plasma cosmologies to come up with a theory that replicates these features in detail remains a major hurdle for the models to overcome.9

Objections to Non-standard Cosmologies

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 easily undergoes nuclear fusion in stars and there are no known astrophysical processes other than the Big Bang itself that can produce it in large quantities. Hence the fact that deuterium is not an extremely rare component of the universe suggests that the universe has a finite age.

Proponents of these non-standard cosmologies argue that there may be some other means by which deuterium can be generated. They further claim that there is no evidence that deuterium is being depleted by stellar fusion.

Theories which assert that the universe has a finite life but that the Big Bang did not happen have problems with the abundance of helium-4. The observed amount of 4He is far larger than the amount that should have been created via stars or any other known process. By contrast, the abundance of 4He in Big Bang models is very insensitive to assumptions about baryon density, changing only a few percent as the baryon density changes by several orders of magnitude. The observed value of 4He appears to be within the range calculated.

This having been said, there are three theoretical issues with Big Bang nucleosynthesis which have some potential of undermining the theory. The first is that the baryon concentration necessary to get an exact match with the current abundances is inconsistent with a universe with mostly baryons. The second is that the Big Bang predicts that no elements heavier than lithium would have been created in the Big Bang, yet elements heavier than lithium are observed in quasars, which presumably are some of the oldest galaxies in the universe. The third problem is since big bang nucleosynthesis produces no elements heavier than lithium, then we ought to see some long lived remnant stars which have no heavy elements in them. We don't.

The standard explanation for the first are that most of the universe isn't composed of baryons. This explanation fits nicely with other evidence of dark matter such as galaxy rotation curves. The standard explanation for the second and third is that the universe underwent a period of massive star formation creating large high mass stars and that without heavy elements, forming low mass red dwarf stars is impossible. This explanation has the feature that it predicts a class of stars that, as of 2004, have not been observed.

Notes

  1. As quasars are considered by most astronomers to be highly luminous, distant cores of AGN, it isn't surprising that the AGN whose galaxy is more easily observable would have a lower redshift.
  2. Some astrophysicists believe that gravitational lensing might be responsible for some examples of quasars in the immediate vicinity of AGN, but Arp and others argue that gravitational lensing cannot account for the quasars' tendency to align along the host galaxies minor axis.
  3. It has been pointed out that it is impossible for this relationship to continue indefinitely. It is a purely observational coincidence in the minds of the vast majority of astrophysicists.
  4. The question of whether quasars are cosmological or not was an active controversy in the late 1960s and early 1970s, but by the late 1970s most astronomers had considered the issue settled. The main argument against cosmological distances for quasars was that the energy required was far too high to be explainable by nuclear fusion, but this objection was removed by the proposal of gravity powered accretion disks.
  5. Arp and others who agree with him have been known to support the argument for a varying non-cosmological redshift by referring to a so-called "magnitude-redshift discrepancy". When a Hubble Law-type plot of quasar magnitudes versus redshift is made, a graph with a diffuse scatter and no clear linear relation is generated. However, since absolute magnitudes can only be independently calibrated to an upper limit using size constraints from variability and an Eddington luminosity, it is likely that quasars are exhibitting differing luminosities that cannot neccessarily be derived from such simplistic first principles. Arp, Burbidge, and others maintain that the scatter in these plots further supports the idea that quasars have a non-cosmological component to their redshift, but nearly everyone else in the field accepts that quasars have variable luminosity.
  6. While it is true that in astrophysics plasma and magnetic effects are considered very important in determining the structure of gas and dust within a galaxy, it is unclear by what mechanism magnetic fields would change galaxy rotation curves and velocity dispersions. Galaxy velocity dispersion measurement come in part from observations of halo stars and it is unclear how a magnetic field would change the orbital motion of a star in an area where there is very little gas and dust.
  7. The structure of the filaments seen in cosmological galaxy surveys are very different than the structure of filaments seen in most plasma processes, and there is no proposed mechanism offered by the alternative model as to why the size of the structures has an upper-limit.
  8. Lerner fails to explain why the electrons should reemit in the best measured blackbody spectrum observed in all of science and how the entire plasma can become thermalized with exposure to anisotropic radiation fields.
  9. There was recently some excitement on the part of certain plasma cosmology adherents over an analysis of WMAP results by researchers at the University of Durham. This analysis proported to show certain variations of microkelvin anisotropies in the WMAP data correspond to the locations of local galactic clusters and superclusters. Fans of Eric Lerner claim that his model predicted similar types of associations. However, this association was predicted in the Big Bang model to be due to the Sunyaev-Zeldovich effect, and the investigation was designed with that in mind.

See also

Creation: Creative evolution, Creation myths, Creationism, modern geocentrism
Other: Anthropic principle, Dirac large numbers hypothesis, De Sitter universe

Bibliography

  • Arp, Halton, "Seeing Red". Apeiron, Montreal. August 1998. ISBN 0968368905
  • Hannes, Alfven D., "Cosmic Plasma". Reidel Pub Co., February 1981. ISBN 9027711518
  • Hoyle, Fred, and Geoffrey Burbidge, and Jayant V. Narlikar, "A Different Approach to Cosmology : From a Static Universe through the Big Bang towards Reality". Cambridge University Press. February 17, 2000. ISBN 0521662230
  • Lerner. Eric J., "Big Bang Never Happened", Vintage Books, October 1992. ISBN 067974049X
  • Mitchell, William C., "Bye Bye Big Bang: Hello Reality". Cosmic Sense Books. January 2002. ISBN 0964318814
  • Narlikar, Jayant Vishnu, "Introduction to Cosmology". Jones & Bartlett Pub. January 1983. IUCAA. ISBN 0867200154
  • Peratt, Anthony L., "Physics of the Plasma Universe". Springer-Verlag, 1991, ISBN 0387975756

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