Non-standard cosmology: Encyclopedia II - Non-standard cosmology - Non-standard cosmologies

Non-standard cosmology - Non-standard cosmologies

There have been a number of non-standard models which have been proposed. Standard responses to some of the claims made in by the variable mass and plasma cosmology proposals are footnoted to the notes section at the end of the article.

Non-standard cosmology - Creationist ideas

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 (Omphalism) 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. Both Young Earth Creationism and Old Earth Creationism have been considered by skeptical organizations and the scientific community to be pseudoscience, junk science, fringe science, or bad science.

Non-standard cosmology - 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.

Non-standard cosmology - 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 [2].

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.

Non-standard cosmology - Variable mass hypothesis and intrinsic redshifts

There remain small numbers of astrophysicists, including Jayant Narlikar, Y.P. Varshni and Halton Arp, who argue that redshifts in galaxies do not correlate with distance and/or are not due to general relativistic effects arising from a universal expansion, and that this invalidates the need for the Big Bang.

Halton Arp, one of the most famous of these astronomers, is an observational astronomer, as such his arguments do not constitute an alternative cosmological model; rather, he maintains that they are a refutation of the Big Bang, and invites theoretical astrophysicists to join him in working out alternative explanations. 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.^[3]
• The quasars tend to lie within a narrow conical zone centered about the minor (rotational) axis of the associated active galaxy.^[4]
• 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.^[5]
• 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.^[6] 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.^[7] 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 exist.

In addition, it is not clear what mechanism would be responsible for intrinsic redshifts, or its supposed gradual dissipation over time. It is also 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 redshifts 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 their associated AGN, though observed metal lines in quasars are notoriously weaker than nearby AGN. Variable luminosity and absorption phenomena such as the Lyman-alpha forest would both be explained by as yet theoretically undeveloped "local means".

Non-standard cosmology - Plasma cosmology

Plasma cosmology is a classic non-standard model developed by Hannes Alfvén, based on laboratory research into plasmas, and applied to cosmological observations. 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.^[8] 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.^[9] In this way, plasma cosmology purports 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.

Alfvén, 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.^[10] 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.^[11]

Non-standard cosmology - Self Creation Cosmology

Self creation cosmology (SCC) theories are an adaptation of the Brans-Dicke theory in which the requirement of the conservation of energy-momentum is relaxed to allow the scalar field to interact with matter and create mass.

The original SCC paper (Barber, G.A. : 1982, Gen Relativ Gravit. 14, 117. 'On Two Self Creation Cosmologies') explored two toy theories of which the first was rejected on the grounds of a gross violation of the equivalence principle, and the second was an early version of the new 2002 theory.

Although the field equations of the new 2002 SCC theory [12] are manifestly covariant, energy is locally conserved in a preferred foliation of space-time that is selected by Mach's principle [13].

The new theory is conformally equivalent to canonical GR in vacuo [14] so that test particles follow the geodesics of GR in solar system experiments. This degeneracy, [15] in which the present tests of GR are equal with those of SCC, may be resolved by three further definitive experiments in which the predictions differ. One of them, the Gravity Probe B geodetic precession, is being evaluated in 2006; SCC predicts 2/3 that of the GR N-S precession, i.e. 4.4096 arcsec/yr.

In its cosmological solution, in which the theory does differ from canonical GR, SCC does not require unknown dark energy, or exotic dark matter, to be concordant with present cosmological constraints. In particular, as an example of a freely coasting model [16], in which the universe expands strictly linearly with time [17], SCC clears basic constraints on nucleosynthesis.

In the Jordan conformal frame of the theory the cosmological solution is closed, static, eternal and singularity free. In this frame rulers 'shrink' and atomic clocks 'speed up' as their atoms exponentially gain mass with cosmological time .

Philosophical problems associated with 'an origin' thus disappear.

Finally, SCC predicts a cosmological 'clock-slip' between atomic clock time and ephemeris time. Consequentially, distant spacecraft should appear to suffer a sunwards acceleration equal to cH, as indeed seems to be observed in the Pioneer anomaly.

Adapted from the Wikipedia article "Non-standard cosmologies", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki