Non-standard cosmology Guide, Meaning , Facts, Information and Description
A non-standard cosmology is a cosmological theory that contradicts the standard model of cosmology. The 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, in practice a non-standard cosmology has primarily meant any cosmological theory which questions the fundamental propositions of the Big Bang theory.
The motivation behind much of non-standard cosmology is the fact that to explain current observations within the framework of the big bang, one must include some seemingly ad-hoc assumptions and inelegant additions. For example, in order to make the big bang consistent with current observations, one would need to postulate the existence of some form of dark matter and dark energy and a phase of rapid expansion known as cosmic inflation. Proponents of non-standard cosmologies argue that these additions to the theory lead to an inelegant system which some have compared to the Ptolematic model of the solar system. By investigating and questioning the basic assumptions of the Big Bang theory, non-standard cosmologies attempt to address these issues from a supposedly empirical framework, even though the foundations of non-standard models might clearly contradict those of the Big Bang theory.
One point that should be noted is that there is not a single non-standard cosmology. Within the category are many different models which often contradict each other. This is in contrast to standard model of cosmology that is designed to be in concordance with the sum total of all cosmological observations (see Lambda-CDM model). While what is considered the standard model of cosmology as opposed to a standard model of cosmology has changed over the years, the general consensus in the scientific community is that with the advent of precision cosmology, model-making in the field is today more of a parameter fitting exercize rather than complete reinvention. 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.
In addition, the term standard can be slightly misleading. For example, it is the case that all of standard cosmologies under serious consideration in 2004 contain physics which is outside the realm of the standard model of particle physics and presume the existence of some form of particle, field, or object that has not been observed. Conversely, proponents of some non-standard cosmologies assert that their models contain no physics which has not been observed, and in fact often cite this fact as evidence in favor of their models.
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 future standard cosmologies. 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 in addition data from COBE and WMAP provided detailed quantitative data which was consistent with standard cosmologies.
The standard cosmologies have asserted that:
Alternative models of cosmology that do not challenge the two assertions above are generally lumped together as standard cosmological models, even if they are not universally accepted. For example, the ekpyrotic universe holds that the expansion of the universe began in the collision of two branes in the higher dimensional "bulk" of brane cosmology. Although radical, this cosmology is an extension of, rather than a detractor of, the big bang theory.
There are a number of general objections to the standard models which have been advanced by supporters of non-standard cosmologies, at one time or another. In addition there are specific objections to the Big Bang. One is that the Big Bang pre-supposes a beginning to the universe and fails to answer the question of what happened before the beginning. This point is considered to be moot by most standard cosmologists, since extrapolation of the universe's behavior before the Planck time is considered to be as yet an unknown area of physics. Whether the Big Bang predicts a singular beginning or an alternative universe without a beginning is not something that current theories of physics can answer for certain. Another objection is that the Big Bang requires esoteric and ad-hoc physics to explain observations. However this last point is not very strong, as even the non-standard cosmologies often employ what could be considered exotic physics to some. Many proponents of standard cosmologies do not deny that problematic issues exist in standard cosmologies. However, they argue that standard cosmologies based on the Big Bang theory are better able to explain these issues than non-standard cosmologies.
With the advent of space-based instruments, along with improved ground-based instruments, we have gained a broader view of the electro-magnetic spectrum during the late 20th century. We are now able to detect frequencies of radiation that where not accessible during the primary period that the Big Bang theory took shape. With each new instrument comes new observations of astrophysical process. In some cases there have been observations which the Big Bang theory does not appear to explain well. However, these observations are handled within the standard models by making refinements and enhancements to the basic Big Bang theory, and so the list of observations which most cosmologists feel are unexplained, changes over time.
Supporters of non-standard cosmologies claim that these modifications and enhancements to the Big Bang theory are ad-hoc and incoherent, and have produced an overly complex and inelegant theory. For instance, it
is generally agreed by astronomers that the big bang model simply cannot agree with observations without
assuming the existence of cosmic inflation which in turn requires the existence of vacuum energy. In addition, it is also agreed that without assuming dark matter that
big bang nucleosynthesis produces a massive underabundance of deuterium, and that without
assuming dark energy that the big bang massively underestimates the age of the universe.
In an 'Open Letter to the Scientific Coummunity,' signed by thirty-three scientists around the world, including Hermann Bondi, and published in the May 22nd 2004 issue of the New Scientist periodical, they protest that: the observation that the Big Bang theory has not been able to provide a basis for quantitative predictions:
Obviously, any question of a scientific nature ought to be answered on the basis of the known and established facts, as far as they can be discovered. There is no doubt that the standard model is the most firmly established cosmological model today, but how well it stands up to alternative, or non-standard models, must always depend on the strength of the alternative's merits in comparison with those of the standard model.
For instance, besides the cosmic microwave background radiation (CMB), a non-standard cosmology must deal with the observation of cosmic redshift (ie., the apparent expansion of the universe.) Also, element distribution and "correlation functions" for the statistics of galactic distribution in the universe, are observations/theory that the standard model successfully addresses, and which big bang cosmologists insist that any non-standard model should be able to answer as well.
During the 1970s and 1980s various observations (notably of galactic rotation curves) showed that there was not sufficient visible matter in the universe to account for the apparent strength of gravitational forces within and between galaxies. Since only gravitational forces are taken into account within the standard model, this led to the idea that up to 90% of the matter in the universe is non-baryonic dark matter. In addition, assuming that the universe was mostly regular matter led to predictions that were strongly
inconsistent with observations. In particular, the universe is far less lumpy and contains far less deuterium than can be accounted for without dark matter. While this idea was initially controversial, it is now a widely accepted part of standard cosmology due to observations in the anisotropies in the CMB, gravitational lensing studies, and x-ray measurements from galaxy clusters.
However, quasi steady-state theory and plasma cosmology have been put forward as alternatives that do not require dark matter to explain the observations of galactic curves. In some versions of plasma cosmology, for instance, the observed galaxy rotation curves are accounted for by the additional electro-magnetic forces and interactions. 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. 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 there has not been offered any non-standard cosmology which explains in detail the totality of proposed evidence for dark matter.
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. Furthermore 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.
More recently (since 1997), observations of supernovae in the distant universe have suggested that a large part of the energy density of the universe consists of a repulsive dark energy (perhaps simply "vacuum energy", but possibly something more complicated) which is causing the expansion of the universe to accelerate. This conclusion has been accepted by most standard cosmologists since it matches the predictions that can be obtained for this effect from completely independent observations of the anisotropies in the CMB. An explanation of the proposed existence of dark matter and dark energy is required in order for any cosmological model to be successfull. Advocates of non-standard models claim there is no need to invoke dark matter or dark energy as gravity is not taken to be the only acting force in the universe.
Any cosmological theory should be able to explain the near-isotropy of the CMB (Cosmic Microwave Background) and should also be able to explain the micro-Kelvin CMB anisotropies measured in detail by the WMAP mission. Standard models invoke a period of inflation in the early universe, the underlying mechanism, although efforts to associate that period of inflation with a specific physical mechanism have been unfruitful.
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. What Lerner fails to explain is 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.
Standard cosmologists also calculate the anisotropies in the CMB and identify a number of features such as peaks and valleys in its power spectrum which correspond to cosmological quantities. WMAP 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 has led most astrophysicists to dismiss them. 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 micro-Kelvin anisotropies in the WMAP data correspond to the locations of local galactic clusters and superclusters. This association was just as predicted by the Sunyaev-Zeldovich effect and was the purpose of the investigation. However, some fans of Eric Lerner claim that his model predicted similar types of associations.
A second alternative explanation, favoured by Steady State theorists, is that the intergalactic medium contains microscopic iron dust particles or whiskers, which can also scatter radio in the same manner to produce an isotropic CMB. However, observational evidence for the existence of these iron particles is yet to appear.
Either of these explanations could potentially free other alternative cosmological models such as general time dilation, steady state models, and so on from the need to explain the isotropy of the CMB, because they transform it into a local effect rather than a cosmological feature.
In the meantime, there are other issues that some non-standard cosmologists insist must also be considered. A good example is the observations made since the 1960s by the astronomer Halton Arp, which offer an alternative to the standard interpretation of quasar formation, redshift and Hubble's Law.
Arp has observed a handful of correlations between quasars (and more recently, X-ray sources from Chandra data) and 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 (examples include NGC 3516 and NGC 5985 as well as M51, NGC 7603, NGC 3370, NGC 4319, NGC 4235, NGC 4258) which all have some properties in common:
These observations indicate to Arp that a relationship may exist between quasars (or at least a certain type of quasar) and AGN. Arp claims that these 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.
The biggest problem with this 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 fact, 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.
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 ignore the observations as either chance or error. Arp himself proposes Narlikar's variable mass hypothesis, which contains alternative explanations of various observed cosmological features, but it remains, at best, incomplete.
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".
A further anomaly comes from the magnitude-redshift relation first discovered by Hubble. Plotting absolute galactic magnitudes against their redshift produces a clear linear relation, which in 1929 led Hubble to propose an expanding universe and Fritz Zwicky to propose the tired light hypothesis. However, quasars were discovered much later, and the same plot done using quasar data produces a much more diffuse scatter with no such clear linear relation. However, since the absolute magnitudes can only be calibrated using a size constraints from variability and an Eddington luminosity limit, it is likely that quasars are exhibbiting differing absolute 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.
There have been a number of non-standard models which have been proposed.
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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.
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. In 1985 it was found that this incompatibility is removed if energy is strictly conserved since then the Einsteinian gravitation simulates exactly the tired light effect together with the associated time dilation. However, conservation of coordinate energy cannot reproduce the isotropic blackbody spectrum observed for the Cosmic Microwave Background.
Halton Arp attributes his observations to the "variable-mass hypothesis", which has its foundations within the frame of steady-state theory and Machian physics. Plasma cosmology is one non-standard model that may be able to account for Arp's empirical data, possibly without the need for the variable-mass. One difference between plasma cosmology and steady-state is that plasma cosmology does not invoke matter creation; rather it invokes the flow of matter between different areas of the universe. In some versions of plasma cosmology, matter is explicitly assumed to have always existed. However, it is noted that matter may have been created at some time in the past, but that confirmation of this is currently and may forever be beyond our empirical methods of investigation. In contrast with plasma cosmology, the variable-mass theory instead invokes constant matter creation from active galactic nuclei, which puts it into the class of steady-state theory.
One non-standard cosmology, an extension of Einsteinian gravitaton, is based on a principle of conservation of energy. Physical modeling predicts that if the principle of conservation of energy is valid on large scales then there must exist general time dilation, an effect that is exponential with distance from the observer slowing of the rate of time. This effect would behave almost exactly like the hypothetical tired light effect except that it produces an exponential time dilation and by that it is undistinguishable from an accelerating expansion of space. As it stands right now, the exponential relation is observed in analysis of supernovae observations, but is attributed by most cosmologists as due to dark energy.
Despite that the possibility of the effect is known at least since 1985 it isn't accepted as real because conservation of energy across macroscopic coordinates (known in physics simply as the principle of conservation of energy) isn't accepted in cosmology due to considerations of the CMB. Instead, in standard cosmology, the expansion of space is accepted as real, though the principle of coordinate conservation of energy in all the rest of physics still holds. The expansion of space and conservation of energy across macroscopic coordinates cannot coexist for observational reasons as there doesn't seem to be enough Hubble redshift to satisfy both.
Generally the violation of the coordinate conservation of energy is required in standard cosmologies because energy densities are considered to be frame dependent. Observations of interactions of the CMB with local physics at cosmological distances seem to confirm that the energy density is frame dependent (increasing with lookback time). This observation cannot currently be explained by general time dilation.
Allowing for general time dilation effectively would recast the stress-energy tensor in Einstein's Field Equations which non-trivially effects the curvature of spacetime. This would have the effect of giving up the Riemannian geometry as the geometry of spacetime and it would require to replace it with Finsler geometry. It would require to drop the condition of symmetry of metric tensor. Einstein postulated dropping this condition in his "On the General Theory of Gravitation" (Scientific American, April 1950). As it stands, there are definite observations of the flatness of the universe that conflict with the suggested recasting of the stress-energy tensor.
General time dilation also doesn't explain features of the Cosmic Microwave Background therefore an additional explanation would be needed to reproduce an isotropic radiation field that approximates a blackbody of temperature 2.73 K to the level of one part in one hundred thousand. Also an additional explanation of the abundances of light elements would be required if the principle of coordinate conservation of energy were accepted also in cosmology.
If this principle were valid it would simulate accelerating expansion of space with Hubble's constant at observer , where G is Newtonian gravitational constant and ρ is density of space, or alternatively , where c is speed of light and R is Einstein's radius of the universe. As it stands, this differs from the standard cosmological value for Hubble's constant by a a factor of . Observationally, there is agreement with the standard value and disagreement with the proposed value for general time dilation.
The predicted numbers for testing the viability of the effect for our universe, assuming its density as , would be for the apparent expansion and for its apparent acceleration. The acceleration of the expansion is observed but its rate is not known precisely enough to base on it the vilability of the effect under discussion, though the observed density of the universe is discordant with general time dilation.
General
This is an Article on Non-standard cosmology. Page Contains Information, Facts Details or Explanation Guide About Non-standard cosmology Standard Models
Non-standard cosmologies minimally challenge one or both of these, usually asserting that one or the other is incorrect.Objections to the Standard Models
However, it's the lack of funding for the support of non-standard research that they decry the most:
For the most part, the accusation of the ad-hoc nature of the Big Bang theory is rejected by standard cosmologists. The observational evidence for inflation, dark matter, and dark energy comes in many different forms from a variety of independent observations. That these indepedent observations are in concordance with each other and that parameter space likelihood analysis shows no mutually exclusive regions makes the claim that the Lambda-CDM model is ad hoc highly dubious. In addition most cosmologists react very strongly against charges that nonstandard cosmologies are being surpressed for ideological reasons and point out that
developing a theoretical model of non-standard cosmology requires no particular large amount of funding, and 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.Dark matter and dark energy
Cosmic Microwave Background
Redshift, AGN, and Quasars
Some astrophysicists believe that gravitational lensing might 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.Non-standard Models
Quasi Steady State Models
Tired Light Models
Plasma Cosmology VS Steady State
The general time dilation
See also
Bibliography
External links and references
Informational
Research articles [ed. full of technical language, but sometimes with introductions in plain English]