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# 2 Is modern cosmology fundamentally wrong?

As a scientist it is essential to question assumptions made by yourself or others. This might mean taking a step back to ask whether the consensus explanations for unsolved problems are right, or whether our underlying models may be fundamentally wrong or incomplete. The gaps in modern cosmological theory, such as the apparent need for dark matter and dark energy, make it especially important to ask such things. The exercise below asks you to read a short article considering these questions.

## Exercise 1

Read the article ‘Dark energy, paradigm shifts, and the role of evidence’ by Lahav and Massimi (2014), and answer the following questions.

1. What do the authors think can be learned from the predictions of Bessel, Le Verrier and Adams in the nineteenth century?
2. What do the paper’s authors think can be learned from the history of particle physics?
3. Do the authors think there is strong evidence that a paradigm shift to a new cosmological model is needed?

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### Discussion

1. It was observed that the orbit of Uranus appeared inconsistent with Newtonian gravity. Bessel postulated that a change in the theory of gravity was needed, whereas Le Verrier and Adams both predicted the existence of an unknown planet. The latter explanation was proved correct with the discovery of Neptune. In contrast, when Le Verrier used similar arguments to postulate the existence of another planet to account for unexpected behaviour in Mercury’s orbit, it transpired that this time the correct explanation was a modification of the theory of gravity, e.g. general relativistic effects. Hence it can require both improvements in observational evidence and in theory to distinguish between different types of explanation for an unexplained phenomenon.
2. Lahav and Massimi argue that there have been several occasions in the past where new particles were required by theory, and then were eventually observed. The discovery of the neutrino is one key example.
3. No – the authors conclude that general relativity and current cosmological paradigm have a large amount of predictive power, and so considerably more evidence would be needed to rule out this model (and/or rule in a better one).

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