My philosophical work focuses on the epistemic status of empirical evidence in cosmology and astrophysics, with a particular focus on dark matter research. Due to the complexity of the evolution of the universe, and the exponential growth of cosmological and astrophysical observations throughout the 20th century, cosmology and astrophysics can shed new light on ongoing debates in philosophy of science. My work draws on and contributes to insights from general philosophy of science as well as to the nascent fields of history and philosophy of cosmology and astrophysics.

Confirming dark matter
The existence of dark matter is well-supported: there is a wide range of empirical evidence for a novel type of matter that has important gravitational effects on the evolution of our universe. But beyond the fact that it has gravitational effects, all that is known is that dark matter is unlike anything studied by particle physics so far. Observations have been limited to dark matter’s effects on remote astrophysical bodies, while any detection in terrestrial experiments remains wanting. Nonetheless, many experiments and observations are underway, trying to uncover dark matter’s fundamental structure. I aim to explicate the success conditions for these experiments: under what conditions can different experiments and observations claim that they have detected dark matter?

1. A first paper on dark matter particle searches argues that the justifications for these particle searches take on a structure different from what is often the case in experimental practice. I argue that this is because of the limited description of dark matter. By illuminating this ‘method-driven logic’, I shed new light on questions surrounding measurement robustness and methodological pluralism in the context of dark matter research. The published version of the paper is available here.
   

Evidence Evaluation: Anomalies on Galactic Scales
A second research area is centered on the small-scale challenges in cosmology. These small-scale challenges are an instance of a recurring challenge for philosophers of science: when does an apparent discrepancy between a theoretical prediction and an empirical observation or between different empirical observations constitute a genuine anomaly (and thus a problem for the theory), and are there contexts where it can temporarily be ignored for the pursuit of other goals? Although many attempts have been made in the past, it seems impossible to formulate universally applicable necessary and sufficient conditions to distinguish the two situations above. Instead, I draw on the history of cosmological practice to make headway on the question of anomalies in context of cosmology and astrophysics.

1. In collaboration with Nora Boyd, I wrote a paper on potential responses to the small-scale challenges for the cosmological concordance model. We argued that, right now, the small-scale challenges do not constitute genuine anomalies for ΛCDM. We further recommended prioritizing further developments of hydrodynamic simulations, based on the principle of epistemic conservatism and the need to identify contributing causal factors. The published version of the paper is available here, a pre-print is available here.
2. In collaboration with Richard Dawid, I wrote a paper on the philosophical debate about dark matter and MOND. Peculiarly, adherents of MOND often criticize dark matter and ΛCDM by appealing to philosophical views on the demarcation problem and theory confirmation. We argue that this defense of MOND, over dark matter, fails: we show that the only plausible reconstruction of the MOND defense is in terms of meta-empirical theory assessment (MEA), but, insofar as the MONDian defense instantiates MEA, it does so in an unsatisfactory way. The paper is available (open-access) here.
   

History of relativistic cosmology: discussions at the BAAS
In collaboration with Mike Schneider
In September 1931, a peculiar event in the history of relativistic cosmology took place. At the Centenary Meeting of the British Association for the Advancement of Science (BAAS), a panel discussion was organized on “The Expanding Universe”. The recorded remarks and press reports of the meeting show a field where multiple foundational questions were far from being settled. And, interestingly enough, at the next meeting of the BAAS two years later, a similar event (although smaller in scale and with less fanfare) was organized. We pursue a detailed study of the foundational debates taking place during the early days of the discipline we now call relativistic cosmology and emerging at the BAAS.

1. A first paper focuses on de Sitter and Georges Lemaître’s diverging responses to the timescale problem, that is, that the evolving universe appeared to be younger than the oldest stars in the universe. We argue that their disagreement is symptomatic of an unsettled foundational question about what role considerations of scale should play in relativistic cosmology. The published version of the paper is available here, a pre-print is available here.
2. In an ongoing project, we turn more explicitly to the 1933 debate, where E.A. Milne's criticism of relativistic cosmology had started to dominate the debate. We investigate what, exactly, Milne's objection to relativistic cosmology was, independently from Milne's development of kinematic relativity.