Black Hole Coalescence: Observation and Model Validation

This paper will discuss the recent LIGO-Virgo observations of gravitational waves and the binary black hole mergers that produce them. These observations rely on having prior knowledge of the dynamical behaviour of binary black hole systems, as governed by the Einstein Field Equations (EFEs). However, we currently lack any exact, analytic solutions to the EFEs describing such systems. In the absence of such solutions, a range of modelling approaches are used to mediate between the dynamical equations and the experimental data. Models based on post-Newtonian approximation, the effective one-body formalism, and numerical relativity simulations (and combinations of these) bridge the gap between theory and observations and make the LIGO-Virgo experiments possible. In particular, this paper will consider how such models are validated as accurate descriptions of real-world binary black hole mergers (and the resulting gravitational waves) in the face of an epistemic circularity problem: the validity of these models must be assumed to justify claims about gravitational wave sources, but this validity can only be established based on these same observations

On the “Direct Detection” of Gravitational Waves

In this paper I provide an account of the sense in which the LIGO-Virgo Collaboration's 2015 observation, "GW150914" constituted the first "direct detection" of gravitational waves. Roughly, my account leverages the conceptual resources from recent work in the philosophy of measurement (especially Parker (2017)’s distinction between direct and derived measurements) to distinguish between these detections at the level of the modeling of the measurement processes. This distinction also has epistemic importance, because the choices scientists make about how to model measurement processes are related to the kinds of interventions they can perform to test the adequacy of their models. The direct/indirect distinction concerns the nature of the justification for confidence in the measurement outcome—in the direct case, this is based primarily on models of the measuring system, while in in the indirect case it also relies on models of a separate target system. Since astrophysical systems are not amenable to interventions, observations of the Hulse-Taylor system, and indeed the source of GW150914, cannot be “direct” in the same way that detections of gravitational waves are

Robustness and the Event Horizon Telescope: the case of the first image of M87*

We examine the justification for taking the Event Horizon Telescope’s famous 2019 image to be a reliable representation of the region surrounding a black hole. We argue that it takes the form of a robustness argument, with the resulting image being robust across variation in a range of data-analysis pipelines. We clarify the sense of “robustness” operating here and show how it can account for the reliability of astrophysical inferences, even in cases—like the EHT—where these inferences are based on experiments that are (for all practical purposes) unique. This has consequences far beyond the 2019 image

The Next Generation Event Horizon Telescope Collaboration: History, Philosophy, and Culture

This white paper outlines the plans of the History Philosophy Culture Working Group of the Next Generation Event Horizon Telescope Collaboration.Comment: 23 pages, 1 figur

The Next Generation Event Horizon Telescope Collaboration: History, Philosophy, and Culture

This white paper outlines the plans of the History Philosophy Culture Working Group of the Next Generation Event Horizon Telescope Collaboration

Key Science Goals for the Next-Generation Event Horizon Telescope

The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing the central compact objects in the elliptical galaxy M87 and the Milky Way. Proposed upgrades to this array through the next-generation EHT (ngEHT) program would sharply improve the angular resolution, dynamic range, and temporal coverage of the existing EHT observations. These improvements will uniquely enable a wealth of transformative new discoveries related to black hole science, extending from event-horizon-scale studies of strong gravity to studies of explosive transients to the cosmological growth and influence of supermassive black holes. Here, we present the key science goals for the ngEHT and their associated instrument requirements, both of which have been formulated through a multi-year international effort involving hundreds of scientists worldwide

Independent Evidence in Multi-messenger Astrophysics

In this paper I discuss the first ``multi-messenger'' observations of a binary neutron star merger and kilonova. These observations, touted as ``revolutionary,'' included both gravitational-wave and electromagnetic observations \emph{of a single source}. I draw on analogies between astrophysics and historical sciences (e.g., paleontology) to explain the significance of this for (gravitational-wave) astrophysics. In particular, I argue that having independent lines of evidence about a target system enables the use of argumentative strategies---the ``Sherlock Holmes'' method and consilience---that help overcome the key challenges astrophysics faces as an observational and historical science

The Next Generation Event Horizon Telescope Collaboration: History, Philosophy, and Culture

Peer reviewed: TrueFunder: Volkswagen FoundationFunder: John Templeton Foundation and the Gordon and Betty Moore FoundationThis white paper outlines the plans of the History Philosophy Culture Working Group of the Next Generation Event Horizon Telescope Collaboration.</jats:p

Key Science Goals for the Next-Generation Event Horizon Telescope

Peer reviewed: TrueFunder: European Union’s H2020 ERC Advanced Grant “Black holes: gravitational engines of discovery”; Grant(s): Gravitas–101052587The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing the central compact objects in the elliptical galaxy M87 and the Milky Way. Proposed upgrades to this array through the next-generation EHT (ngEHT) program would sharply improve the angular resolution, dynamic range, and temporal coverage of the existing EHT observations. These improvements will uniquely enable a wealth of transformative new discoveries related to black hole science, extending from event-horizon-scale studies of strong gravity to studies of explosive transients to the cosmological growth and influence of supermassive black holes. Here, we present the key science goals for the ngEHT and their associated instrument requirements, both of which have been formulated through a multi-year international effort involving hundreds of scientists worldwide.</jats:p

Key Science Goals for the Next-Generation Event Horizon Telescope

The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing the central compact objects in the elliptical galaxy M87 and the Milky Way. Proposed upgrades to this array through the next-generation EHT (ngEHT) program would sharply improve the angular resolution, dynamic range, and temporal coverage of the existing EHT observations. These improvements will uniquely enable a wealth of transformative new discoveries related to black hole science, extending from event-horizon-scale studies of strong gravity to studies of explosive transients to the cosmological growth and influence of supermassive black holes. Here, we present the key science goals for the ngEHT and their associated instrument requirements, both of which have been formulated through a multi-year international effort involving hundreds of scientists worldwide