The Hubble-Lemaître constant: is it really a constant?

Following an open debate, the International Astronomical Union recently recommended that the rate of expansion of the universe, traditionally referred to as the "Hubble Constant", should henceforth be referred to as the "Hubble-Lemaître Constant". In this session we will see why the change of designation was necessary to do justice to the work of Georges Lemaître, one of the fathers of relativistic cosmology, but also the reasons that point out that in reality it is not a constant.