Understand
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.