Philosophy of Astrophysics

Observing the Invisible: A Collaborative Investigation between Astrophysicists and Philosophers

I am currently a postdoctoral researcher in the Philosophy Department at the University of Pennsylvania working with Dr. Michael Weisberg and astrophysicist Dr. Barry Madore (The Carnegie Observatories) on an NSF-funded project Observing the Invisible: A Collaborative Investigation between Astrophysicists and Philosophers (Award No.1557138).

This project is a collaborative investigation between astrophysicists and philosophers of science that focuses on the astrophysical notion of dark matter, which does not produce or interact with light (or, more broadly, electromagnetic radiation). Astrophysicists believe that twenty-five percent of the universe is composed of dark matter, but they don’t know what dark matter is or where most of it resides. The guiding empirical hypothesis of this project is that some dark matter resides in dark galaxies; that is to say, in dark matter halos that either never possessed or have lost their ordinary matter at some time in the past. The project involves searching for these dark galaxies and studying the unique blend of observation, simulation, theory, and reasoning that allows astrophysicists to make such a discovery

 

.

Similarity, Adequacy, and Purpose: Understanding the Success of Scientific Models

My dissertation examines properties models should possess in order to justify scientific inferences made from them. I examine earlier philosophical accounts of how to assess and evaluate models, criticize them failing to distinguish different dimensions along which models should be evaluated, and propose a new framework for evaluating models. I then apply this framework to several case studies from astrophysics. While completing my dissertation, at Western Ontario, I also participated in the Rotman Institute of Philosophy’s Cosmology Project with Chris Smeenk.

Full dissertation can be downloaded here.

Dissertation Abstract: A central component to scientific practice is the construction and use of scientific models. Scientists believe that the success of a model justifies making claims that go beyond the model itself. However, philosophical analysis of models suggests that drawing inferences about the world from successful models is more complex. In this dissertation I develop a framework that can help disentangle the related strands of evaluation of model success, model extendibility, and the ability to draw ampliative inferences about the world from models.

I present and critically assess two leading accounts of model assessment, arguing that neither is sufficient to provide a complete understanding of model evaluation. I introduce a more powerful framework incorporating elements of the two views, which can help answer these three questions: What is the target of evaluation in model assessment? How does that evaluation proceed? What licenses us in making inferences about the real world, based on the evaluation of our models as successful?

The framework identifies two distinct targets of model evaluation: representational similarity between the model and target system, and the adequacy of the model as a tool to answer questions. Both assessments must be relativized to a purpose, of which there are three general kinds: descriptive, predictive, and explanatory. These purposes differ in the way they inform the similarity relation, which is relevant for the similarity assessment, and the output they produce, which is relevant for the adequacy assessment. Any model can be assessed relative to any purpose, however a model encodes certain decisions made during the model’s construction, which impact its ability to be applied to a new purpose or new domain. My framework shows that extending a model, and drawing inferences from it, depends on its representational similarity.

I apply this framework to several examples taken from astrophysics showing in detail how it can help illuminate the structure of the models, as well as make the justification for inferences made from them clear. The final chapter is a detailed analysis of a contemporary debate surrounding the use of models in astrophysics, between proponents of MOND and the standard ΛCDM model.