The problem with the Hubble constant

Cosmic Microwave Background Radiation
NASA-WMAP

The Hubble constant, which measures the speed of expansion of space in the universe, has very curious properties. For instance, although we call it constant, it turns out that it is not a constant, as it varies over time. That is why its current value is represented by the symbol H₀, but since its value was different at other times, it can be represented by other symbols, such as H_CMBR, which refers to its value at the time when the cosmic microwave background radiation originated, about 13.7 billion years ago.

A photograph from the abyss of time

The cosmic background radiation as detected by the Planck satellite telescope

When the space telescopes sent by NASA and the European Space Agency (COBE, WMAP, Planck) send us data on the cosmic background radiation, the corresponding images usually appear on the first page of high-diffusion newspapers, accompanied by headlines that are not always correct. Let's look at a few, published in Spanish newspapers: