The Unsettled Number: Hubble's Tension

Understand

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.