Every distant galaxy is rushing away from us, and the further away, the faster

In 1929, Edwin Hubble plotted galaxy distances against their light's redshift and found a startlingly clean pattern: recession speed rises with distance. It was the first direct observational evidence that the universe is expanding, turning Lemaître's theoretical proposal into measured fact.

— Edwin Hubble, A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae — Proceedings of the National Academy of Sciences, 1929