What if the universe isn’t expanding?
The Big Bang, Fred Hoyle’s derisive description of several cosmological theories that posit a beginning of the universe, was theorized because the universe was shown to be expanding. Edwin Hubbell found in 1929 that the “red shift” of stars was proportional to their distance. Since the electromagnetic waves of stars are lengthened (or pushed towards the red end of the spectrum) the further the star is from the Earth observer, the thinking is that stars are receding from the Earth and receding at a faster rate the more distant they are. This implies that the universe is expanding like the surface of a ball being inflated.
Now, since time is thought to be reversible (or at least that there is a symmetry about time), then if you reverse time you see that the universe contracting until it reaches its smallest point a singularity, which is the state of the universe before the so-called Big Bang.
Several observational problems of such a theory have been patched over by positing an extremely brief period of “inflation,” during which at the very beginning of the universe there was an extremely great expansion followed by expansion at a slower rate and by “dark energy” which is posited to account for the unexpectedly rapid recession of certain types of supernovae discovered in the 1970s. Because the amount of “dark energy” needed is extremely large, and because there has been no observation of it, some have considered it a major fudge factor and have tried to envision a cosmology without it and without an origin like the Big Bang. We commented on one such model here.
Cornell’s Physic’s arXiv Blog today reports on another. This one by the University of Sydney’s David Crawford. His paper, entitled “Observational evidence favours a static universe,” can be accessed in a number of formats here. (It’s perhaps worth noting again that papers in arXiv are not peer-reviewed; it’s perhaps unnecessary to observe that neither were Newton’s works.)
Crawford argues that the observed red shift is not evidence of an expanding universe but can be explained by what he calls “curvature cosmology.” Crawford describes this theory as “a static tired-light cosmology where the Hubble redshift (and many other redshifts) is produced by an interaction of photons with curved spacetime called curvature redshift” (p26). He says, however, that the difference between curvature cosmology and any of the Big Bang cosmologies comes down to whether or not expansion has and is taking place, the critiques he makes apply in favor of any steady-state hypothesis.
He argues that existing interpretation of the evidence for expansion suffers from the bias of presupposing a Big Bang. (Interestingly, even Hubbell’s original detection of the red shifts took place after Georges Lemaître had already proposed the “hypothesis of the primeval atom” (the Ur-Big Bang theory)). This is what Crawford says about bias:
“A problem in evaluating a well established cosmology like Big Bang cosmology is that all of the observations have been analysed within the BB paradigm. Thus there can be subtle effects that may lead to a possible bias. In order to avoid this bias and wherever possible comparisons are made using original observations” (p1).
Crawford tries to lay out the cards in Section 3, where he identifies the “problems” of Big Bang theories as: inflation, dark matter and dark energy and of his version of Steady State theory as: red-shift curvature and curvature pressure.
Crawford’s theory depends on 2 hypotheses: The first hypothesis is that red shift of distant objects can be accounted for by the interaction of photons with curved space. This, he maintains, is both testable and, he says, is confirmed by X-ray background radiation. He explains:
“The first hypothesis is that the Hubble redshift is due to an interaction of photons with curved spacetime where they lose energy to other very low energy photons. Thus it is a tired-light model. It assumes a simple universal model of a uniform high temperature plasma (cosmic gas) at a constant density. The theory has a good fit to the background X-ray radiation between the energies of 10–300 keV” (p3).
The second hypothesis is that there is “curvature pressure” to stabilize a static state universe. “This hypothesis leads to modified Friedmann equations which have a simple solution for a uniform cosmic gas” (p4). He says that with curvature pressure his theory provides results “identical to that for Einstein’s static universe. For a static universe, there is no ambiguity in the definition of distances and times. One can use a universal cosmic time and define distances in light travel times or any other convenient measure” (p4).
I’ll leave the rest to the reader to ponder by reading the original paper. I have to say that I myself don’t have much of a rooting interest one way or the other. If you want to see “When physicists go wild,” however, you should read the comments section of the arXiv blog. It appears to be to physics what a tea party is to public policy.