A crack in the track of the Hubble Constant

TL;DR

This paper discusses the controversy over measuring the Hubble constant, emphasizing the importance of proper uncertainty management and proposing a methodological framework to improve measurement reliability and address the current Hubble tension.

Contribution

It introduces a methodological guide for identifying, quantifying, and reducing uncertainties in astrophysical measurements, aiming to clarify the Hubble tension debate.

Findings

Highlights misconceptions in current measurement approaches

Proposes a framework for better uncertainty management

Aims to reframe the Hubble tension discussion

Abstract

Measuring the rate at which the universe expands at a given time -- the 'Hubble constant' -- has been a topic of controversy since the first measure of its expansion by Edwin Hubble in the 1920's. As early as the 1970's, Sandage et de Vaucouleurs have been arguing about the adequate methodology for such a measurement. Should astronomers focus only on their best indicators, e.g., the Cepheids, and improve the precision of this measurement based on a unique object to the best possible? Or should they 'spread the risks', i.e., multiply the indicators and methodologies before averaging over their results? Is a robust agreement across several uncertain measures, as is currently argued to defend the existence of a 'Hubble crisis' more telling than a single one percent precision measurement? This controversy, I argue, stems from a misconception of what managing the uncertainties associated with such experimental measurements require. Astrophysical measurements, such as the measure of the Hubble constant, require a methodology that permits both to reduce the known uncertainties and to track the unknown unknowns. Based on the lessons drawn from the so-called Hubble crisis, I sketch a methodological guide for identifying, quantifying and reducing uncertainties in astrophysical measurements, hoping that such a guide can not only help to re-frame the current Hubble tension, but serve as a starting point for future fruitful discussions between astrophysicists, astronomers and philosophers.