Preposterous Universe

 
Alternative cosmologies

A while back Scott Hughes pointed me to the web page of the Alternative Cosmology Group. (Scott, what did I ever do to you?) These are folks who don't really believe in the Big Bang model. The Big Bang is simply the idea that we live in a universe which is nearly homogeneous and isotropic, and has been expanding from a hot, dense state for the last several billion years. Evidence for this model is overwhelming, starting with the fundamental successes of the Hubble Law (distance proportional to velocity for nearby galaxies), the existence of the cosmic microwave background radiation (a relic from the early hot state), and the primordial abundance of light elements (a signature of nucleosynthesis when the universe was about a minute old). More recently, specific models within the Big Bang framework have scored fantastic empirical successes at explaining anisotropies in the microwave background, the characteristics of large-scale structures, the age of the universe, and so on. And patient experts continue to slap down various proposed alternatives. Still, there are doubters. Remind you of any other famously successful scientific theories?

It's fun to go through the introductory paragraph of the Alternative Cosmology Group web site, searching for true statements. Fun, but not especially rewarding.

The Alternative Cosmology Group (ACG) was initiated with the Open Letter on Cosmology written to the scientific community and published in New Scientist, May 22, 2004.

Hey, that one's true! The ACG was initiated with that letter. As far as I know, anyway. (It's all downhill from here.)

The letter points to the fundamental problems of the Big Bang theory, and to the unjustified limiting of cosmological funding to work within the Big Bang framework.

No, it doesn't, since the problems are not fundamental, and the limiting is perfectly justified. We're short of funding as it is; why spend money on theories that have been disproven?

The epicyclic character of the theory, piling ad-hoc hypothesis upon hypothesis, its incompleteness and the appearance of a singularity in the big bang universe beginning require consideration of alternatives.

No, they don't. Various hypotheses may or may not be ad-hoc, but they are simply required to fit the data. We should certainly be looking for ways to go beyond the currently favored version of the Big Bang model by reducing the number of hypotheses, and tying up some of the loose ends, but any such theory will simply be an improved version of the model. You won't replace the fact that the universe is expanding from an initial hot, dense state.

This has become particularly necessary with the increasing number of observations that contradict the theory's predictions.

No, it hasn't, since there are no such observations.

Big Bang cosmology has been in a crisis since the early 90's when the Cold Dark Matter model began to fail.

No, it hasn't. The most restrictive possible version of the "Cold Dark Matter Model," in which there was a critical density of matter particles, was indeed in trouble by the early 90's. Those troubles were resolved in 1998 when it was discovered that the universe is accelerating, implying the existence of dark energy. The "Standard CDM" model was swiftly replaced by the "Lambda-CDM" model (Lambda standing for the cosmological constant), and problems with structure formation and the age of the universe were resolved in one fell swoop. The Big Bang model itself, of course, was never in trouble at all. (A persistent error on the part of critics is to confuse particular scenarios within the Big Bang framework with the framework itself.)

Fifteen years later, this crisis has worsened, despite the addition of dark energy.

No, it hasn't. To the extent that it ever existed, it has gone away. Dark energy, like it or not, keeps being verified by new and independent measurements.

Observations fail to show the dramatic differences between the high-redshift and local universe required by the Big Bang theory.

No, they don't. This is obviously false. What are they thinking?

We still find normal galaxies, heavy elements, strings and clusters of galaxies at the further and further shifting outskirts of the observable universe.

No, we don't. Of course, it is hard to make precise measurements of ultra-distant objects, but to the extent that we can, they look different than nearby objects. Galaxies look different, elemental abundances look different, the density of various objects looks different, everything you would expect in an evolving universe.

The anisotropy of the cosmic background radiation, the existence of very large-scale structures, the cosmic anisotropy to electromagnetic wave propagation are among many observations that contradict Big Bang expectations.

No, they aren't. The first of these two phenomena are manifestly consistent with the Big Bang, and the third one doesn't exist.

At the same time, non-Big Bang alternatives have increasingly shown promise to coherently explain the observations and to predict new phenomena.

No, they haven't. It would be more accurate to say "non-Big-Bang alternatives have continued to make no new correct predictions, while remaining inconsistent with well-established laws of physics."

We believe, therefore, that a shift in effort in cosmology to these alternatives is essential if the field is to advance.

Yes, you do believe that! But it's not true. So only half credit there.

The good news is, the crackpots are planning to get together at a conference. I am sure it will be an entertaining event. The thing about crackpots is, they are usually not mutually self-reinforcing; there are a potentially infinite number of directions in which one can be idiosyncratically mistaken, and crackpottery tends to diffuse through the space. So they aren't likely to be happy with one another's ideas. But at least they will be able to take refuge in a common feeling of persecution by the all-powerful Big Bang Establishment.

~ posted by Sean Carroll at 12:03 AM ~ link ~ ~ ~