This is a short reaction piece to a talk titled ‘What do we really know about the UHECR?’ by Dr. Etienne Parizot at the Interdisciplinary Conference ‘Contested Astrophysics’ on Tuesday the 12th of April 2016 in the Dublin Institute of Advanced Studies in Dublin. UHECR refers to ultra high energy cosmic rays which are cosmic particles with a kinetic energy greater than 1×1018 eV. For a nice introduction to cosmic rays see this link (Prof. Alan Watson). This talk was given as part of a wider interdisciplinary project concerning expert disagreement ‘When Experts Disagree’. Astrophysics was chosen as a relatively ‘clean’ reference point for a case study on expert disagreement given its distance from political and economic motivations. I sat in as an observer. I don’t have access to the talk nor do I have details of all that went on. This is a brief summary and description of observations I made that day.
The room was filled with a modest but respectable number of astrophysicists, philosophers and at least one anthropologist, the latter being myself. Sat at the front was one especially prominent academic, a former astronomer royal, Prof. Arnold Wolfendale. To such a diverse and illustrious audience Etienne presented his paper. Much of the science was lost on me but its central points were nonetheless interesting. For many years Etienne said UHECR were believed to be protons. Of course this could have been the case, he argued, but the conviction of some researchers led to the pursuit of this hypothesis in the face of contradictory evidence. The empirical evidence of UHECR activity, he argued, suggested that it might be other heavier nuclei, such as iron, rather than protons. This ‘proton prejudice’, as he called it, led to interpretations of observational data that supported the proton theory. His only explanation was that this was down to simple human foibles which caused this prejudice. For example, the appeal to authority of the researchers who put forward these hypotheses, the fact that researchers had staked their reputations on this being the case, and so on. In an area as highly empirical as this, it was interesting to see how researchers could still fall victim to the less reasonable quirks of human psychology. Astrophysics may be largely a ‘clean’ reference point, but it is nonetheless framed by the normative as well as ontological and epistemological values of the researchers, which includes the motivations for why researchers decided to do the work they spend their lives on.
Where the talk became more interesting still, was in an unexpected development. As Etienne discussed how UHECR activity is measured a disagreement broke out between two older physicists, Wolfendale being the more combative, and Etienne, over the use of definitions. No one disagreed vocally with the thesis of his paper, despite his cautionary introductory slide ‘These are highly subversive slides’, but with certain definitions. Etienne noted that the methods for recording UHECR were indirect. The detectors on the ground (illustrated in the image below) measure the activity of the streams of particles that hit them. As the UHECR cannot be directly observed, it is by inference from the activity of the particles in the atmosphere they affect, that information about them is obtained. Etienne stated that the data obtained on the ground was about the activity of the particles observed, not the UHECR themselves. This meant, at least from my perspective, that interpretations were built into the data. The two older physicists fundamentally disagreed on this take on the data. For them this was data about the UHECR. There was then a disagreement on what an observation was, and what constitutes a model. There was some heated discussions as Etienne attempted to give his talk. This development was completely unexpected and intrigued me considerably. That definitions as seemingly innocuous as data, model, etc., could be so emotive gave me great insight into how disagreements can unfold. Astrophysics was not so technical and dry in its deliberations as I had suspected (though I had also been aware of how profound it is in its implications for our understanding of the cosmos), but like other disciplines of research, it is dynamic and evolving. Etienne, in a striking aside directed at non-physicists in the room, stated ‘Now, you see us, naked before you’, alluding to the unfolding activity before us, which is not readily witnessed outside of these discussions in how astrophysicists communicate publicly, through publications in journals, books and documentaries. I felt lucky to be a fly on the wall for this moment.
UHECR ground detectors
So what conclusions can be drawn from this example. On a simplistic level you might state that disagreement over what UHECR are, and where they come, and even on the use of definitions, is indicative of science being a matter of opinion or that scientists can’t even agree on what they are looking at. This argument is often thrown about, for example, by politically or fiscally motivated persons who want to reject climate science because of vested interests, association of a branch of scientific expertise with a political stance etc., (see this rather funny John Oliver spoof video on the climate change debate). Religious opposition to evolutionary science, often takes up points of disagreement amongst biologists on the exact details of evolution, as evidence against it. This is often framed as there being no consensus in science on key issues, and so scientific opinion can be disregarded. This view of science is overly simplistic and often deliberately contrarian on the part of cynical parties. Nothing about the example discussed above speaks to deep unresolvable differences between researchers. The subject matter of astrophysics is inherently complex, by many orders of magnitude, that supports differing interpretations at multiple levels. Disagreements are to be expected until the accumulation of empirical evidence supports one view or another. Of course some researchers will never accept a new and often better interpretation, whether this is due to loyalty to an idea, the conviction that their work is correct, the desire to keep their faculty position etc. For some of these researchers it is only with their retirement and eventual death that their interpretations die with them. On a less moribund note, what is laudable about this process is the eventual acceptance of the better interpretation once there are clear reasons for accepting it. Local disagreements, at their best, spur on new ideas by challenging people’s convictions, their interpretations of the data, thus hopefully leading to better science.