Kuhn and the structure of cosmological revolutions

02Sep10

I love how, when I think or read about cosmology, I can clearly see Thomas Kuhn’s framework of science (presented in his book, The Structure of Scientific Revolutions, 3rd ed., 1996).

The Big Bang theory is the cosmological paradigm; it has been since it ‘won’ the debate against Steady State theory back in the ‘70s. I’ll write about this properly soon, I hope; I’ve actually got a book on request at the university library on this topic, which should have been returned almost two weeks ago! How annoying. This controversy alone will be interesting to analyse…

Controversies can arise when observations turn up anomalies in the theory; that is, when “nature has somehow violated the paradigm-induced expectations”. Certainly this has happened, and still happens, to the Big Bang theory. One example that I’ve mentioned in a previous post is the 1991 observation of the size of superclusters, indicating their ages to be older than the predicted age of the Universe. Uh oh! When anomalies occur, Kuhn believes that there are two ways for them to be “made sense of” within a paradigm: the anomaly can be rejected or excused, otherwise the paradigm must be revised or reconsidered; the latter leads to moments of crisis within a paradigm. There are then three ways to resolve the crisis: putting it in the “too hard” basket, dealing with it and retaining the paradigm, or adopting a new paradigm.

Now, in The Big Bang Never Happened (1st Vintage Books ed., 1992), Lerner appeared perturbed that cosmologists added new hypotheses to the Big Bang theory when anomalies such as the supercluster ages arose, or even—shock, horror!—dismissed the anomalies altogether. But, according to Kuhn, this is the nature of science. I’m inclined to side with Kuhn; what’s wrong with adding hypotheses to a theory when you uncover more details about the world? If it works, it works, right? Furthermore, if it’s not possible to determine whether an anomaly can or cannot be dealt with within the paradigm due to limitations in technology, why wouldn’t it be legitimate to set aside these anomalies for future scientists to work with? I have a feeling that this is happening right now.

Clearly, the Big Bang paradigm has not yet been overthrown, despite numbers of alternative candidates being produced as a result of anomalies and controversies (albeit minor) ensuing as a result of the disputes between observation and theory. Why? Because the Big Bang theory still does better than the others observationally, successfully explaining expansion, the cosmic microwave background, and the light elements; although, I’m sure some would argue this. As a Big Bang cosmologist once said to Lerner,

We all know that the Big Bang has many problems. But if there is no alternative, we must stick with it.

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