The Unsettled Number: Hubble's Tension

Abstract

One of main sources of uncertainty in modern cosmology is the present rate of the universe's expansion, H0, called the Hubble constant. Once again, different observational techniques bring about different results, causing new 'Hubble tension'. In the present work, we review the historical roots of the Hubble constant from the beginning of the twentieth century, when modern cosmology originated, to the present. We develop the arguments that gave rise to the importance of measuring the expansion of the Universe and its discovery, and we describe the different pioneering works attempting to measure it. There has been a long dispute on this matter, even in the present epoch, which is marked by high-tech instrumentation and, therefore, in smaller uncertainties in the relevant parameters. It is, again, currently necessary to conduct a careful and critical revision of the different methods before one invokes new physics to solve the so-called Hubble tension.

52 pages, 14 figures, 3 tables. We corrected typos and references

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• Late-time Background Constraints on Linear and Non-linear Interacting Dark Energy after DESI DR2
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• Effect of Peak Absolute Magnitude of Type Ia Supernovae and Sound Horizon Values on Hubble Tension using DESI results
• A test for the redshift dependence of ${\sigma }_8$ using $f{\sigma }_8$ measurements
• Comparison of $\Lambda$CDM and $R_h=ct$ with updated galaxy cluster $f_{gas}$ measurements using Bayesian inference
• Cosmology in warped massive gravity
• Use of Redshifts as Evidence of Dark Energy