Highlights

Abstract

Keywords

۱٫ Introduction

۲٫ The EHT laboratory

۳٫ Coincidence and comparison

۴٫ Concluding remarks

Acknowledgments

References

Abstract

This paper discusses some philosophical aspects related to the recent publication of the experimental results of the 2017 black hole experiment, namely the first image of the supermassive black hole at the center of galaxy M87. In this paper I present a philosophical analysis of the 2017 Event Horizon Telescope (EHT) black hole experiment. I first present Hacking’s philosophy of experimentation. Hacking gives his taxonomy of elements of laboratory science and distinguishes a list of elements. I show that the EHT experiment conforms to major elements from Hacking’s list. I then describe with the help of Galison’s Philosophy of the Shadow how the EHT Collaboration created the famous black hole image. Galison outlines three stages for the reconstruction of the black hole image: Socio-Epistemology, Mechanical Objectivity, after which there is an additional Socio-Epistemology stage. I subsequently present my own interpretation of the reconstruction of the black hole image and I discuss model fitting to data. I suggest that the main method used by the EHT Collaboration to assure trust in the results of the EHT experiment is what philosophers call the Argument from Coincidence. I show that using this method for the above purpose is problematic. I present two versions of the Argument from Coincidence: Hacking’s Coincidence and Cartwright’s Reproducibility by which I analyse the EHT experiment. The same estimation of the mass of the black hole is reproduced in four different procedures.

۱٫ Introduction

In April 2019, an international collaboration of scientists presented Event Horizon Telescope (EHT) observations collected in April 2017 of the radio source at the center of the galaxy Messier 87 (M87). The galaxy M87 has long been known from theoretical models and computer simulations to host a bright, radio source at its center with a supermassive black hole hypothesized to power this radio source. The M87 black hole is considered one of the two largest supermassive black holes in the sky along with the Sagittarius (Sgr) A black hole, a black hole at the center of the Milky Way, near the border of the constellations Sagittarius and Scorpius. Over 200 scientists across the world contributed to the EHT project. Observations were made with sufficient sensitivity to reconstruct images that show a bright orange-yellow asymmetric ring surrounding a dark shadow (a “crescent”). In 2019 the EHT Collaboration published its findings in six scholarly letters (EHT Collaboration 2019a, henceforth EHTC).

In this paper, I present a philosophical analysis of the EHT black hole experiment. I refer mainly to the philosophy of experimentation of Ian Hacking (Hacking 1983, 1988, 1989, 1992), Bas van Fraassen (van Fraassen 1980, 1989, 2001), Nancy Cartwright (Cartwright, 1991) and Peter Galison (Galison, 2019).

The rest of the paper is organized as follows. In Chapter 2, I first present Hacking’s philosophy of experimentation. Hacking gives his taxonomy of elements of laboratory science and distinguishes a list of elements. I use examples from the EHT experiment to illustrate that the EHT experiment conforms to major elements from Hacking’s list.

I then describe with the help of Galison’s Philosophy of the Shadow how the EHT Collaboration created the famous black hole image. Galison, a member of the EHT Collaboration, outlines three stages for the reconstruction of the black hole image: Socio-Epistemology, Mechanical Objectivity, after which there is an additional Socio-Epistemology stage. The Socio-Epistemology and Mechanical Objectivity stages form a cyclic loop (Galison, 2019).