Non-standard cosmology

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 background radiation (CBR) 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.

Proponents of non-standard cosmologies claim that there are some observational and theoretical results, along with laboratory and space-based experimental results, which are difficult to explain within the standard model. Non-standard cosmologies attempt to address these issues from a framework which is not in contradiction to empirical observation and experiment, even though the foundations of non-standard models might clearly contradict those of standard models.

One point that should be noted is that there is not a single standard cosmology nor is there a single non-standard cosmology. Within each of these two categories are many different models which often contradict each other. This can lead to confusing terminology. For example, it is the case that all standard cosmologies contain physics which is outside the realm of the standard model of particle physics. Conversely, proponents of some non-standard cosmologies assert that their models contain no exotic physics, and in fact often cite this fact as evidence in favor of their models.

Standard Models

The standard cosmologies have asserted that:

• redshifts observed in distant galaxies are due to the expansion of the universe
• this expansion is due to the expansion of space as predicted by general relativity

Non-standard cosmologies minimally challenge one or both of these, usually asserting that one or the other is incorrect.

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.

Objections to the Standard Models

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, while mostly non-ad-hoc, 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, many of these observations have been 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, has changed 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, in an 'Open Letter to the Scientific Coummunity,' signed by thirty-three cosmologists around the world, including Hermann Bondi, and published in the May 22nd 2004 issue of the New Scientist periodical, they protest that:

Without the hypothetical inflation field, the big bang does not predict the smooth, isotropic cosmic background radiation that is observed, because there would be no way for parts of the universe that are now more than a few degrees away in the sky to come to the same temperature and thus emit the same amount of microwave radiation.

They also insist that the so-called 'dark matter' and 'dark energy' are just more ad hoc 'fudge factors' designed to preserve the Big Bang theory:

Without some kind of dark matter, unlike any that we have observed on Earth despite 20 years of experiments, big-bang theory makes contradictory predictions for the density of matter in the universe. Inflation requires a density 20 times larger than that implied by big bang nucleosynthesis, the theory's explanation of the origin of the light elements. And without dark energy, the theory predicts that the universe is only about 8 billion years old, which is billions of years younger than the age of many stars in our galaxy.

They go on to add to these indictments, the observation that the Big Bang theory has not been able to provide a basis for quantitative predictions:

What is more, the big bang theory can boast of no quantitative predictions that have subsequently been validated by observation. The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centred cosmology of Ptolemy needed layer upon layer of epicycles.

However, it's the lack of funding for the support of non-standard research that they decry the most:

Supporters of the big bang theory may retort that these theories do not explain every cosmological observation. But that is scarcely surprising, as their development has been severely hampered by a complete lack of funding. Indeed, such questions and alternatives cannot even now be freely discussed and examined. An open exchange of ideas is lacking in most mainstream conferences. Whereas Richard Feynman could say that "science is the culture of doubt", in cosmology today doubt and dissent are not tolerated, and young scientists learn to remain silent if they have something negative to say about the standard big bang model. Those who doubt the big bang fear that saying so will cost them their funding.

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 challenger's merits in comparison with those of the standard model. However, this is proving to be no small feat.

For instance, besides the cosmic background radiation (CBR), 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 that the standard theory successfully addresses, and which big bang cosmologists insist that any non-standard model should be able to answer as well.

Dark matter and dark energy

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 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. While this idea was initially controversial, it is now a widely accepted part of standard cosmology. However, non-standard theories such as Modified Newtonian Dynamics (MOND), steady-state theory and plasma cosmology have been put forward as alternatives that do not require dark matter to explain the observations.

More recently (since 1997), and also within the standard big bang model, 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 (possibly simply "vacuum energy", but possibly something more complicated) which is causing the expansion of the universe to accelerate. This conclusion has been rapidly accepted by most big bang, standard cosmologists. Currently, an explanation of the existence of dark matter and dark energy is now considered to be a major requirement that any successful cosmological model must meet. However, in most non-standard models, 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. In plasma cosmology, for instance, the observed galaxy rotation curves are accounted for by the additional electro-magnetic forces and interactions.

Cosmic Microwave Background

Any non-standard cosmology should be able to explain the isotropy of the CMB (Cosmic Microwave Background). Alfven, Learner and others working within plasma cosmology have shown that the temperature, isotropy, and non-polarisation of the CMB can be readily explained by the diffusion of galactic radio emission by diffuse intergalactic plasma, muc