he saw that galaxies were moving away from each other at a rate constant to the distance between them (Hubble's Law). The further away they were, the faster they receded. This led to the ...

The Hubble constant is one of the most important numbers in cosmology because it tells us how fast the universe is expanding, which can be used to determine the age of the universe and its history. It ...

This proportionality between galaxies' distances and redshifts is today termed Hubble–Lemaître's law. Because the universe appeared to be uniformly expanding, Lemaître further realized that ...