Science is advancing rapidly. We are eradicating diseases, venturing further into space and discovering a growing zoo of subatomic particles. But cosmology – which is trying to understand the evolution of the entire universe using theories that work well to describe other systems – is struggling to answer many of its most fundamental questions.
We still have no idea what the vast majority of the universe is made of. We struggle to understand how the Big Bang could suddenly arise from nothing or where the energy for "inflation", a very short period of rapid growth in the early universe, came from. But despite these gaps in knowledge, it is actually human nature – our tendency to interpret data to fit our beliefs – that is the biggest threat to modern cosmology.
The picture of the cosmos we now have is one that is dominated by two components, dark matter and dark energy. These account for 95% of the energy content of the universe, yet we do not know what they are. This is an issue for cosmologists and indeed is rightly lauded as one of the most important problems in physics – explanations for the nature of dark energy range from proposals to scrap Einstein's theory of relativity, the addition of a new fundamental field of nature, or even that we may be seeing the effects of neighbouring parallel universes.
But the dark energy problem is not the one that threatens to undermine cosmological experiments. In cognitive science, confirmation bias is the effect where people tend to unconsciously interpret information in a manner that leads to a selection of data that confirms their current beliefs. For cosmologists, this means the unconscious (or conscious) tuning of results such that the final cosmological interpretation tends to confirm what they already believe. This is particularly pernicious in cosmology because unlike laboratory-based experiments we cannot rerun our experiment many times to investigate statistical anomalies – we only have one universe.
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