Expansion of the Universe

Edwin Hubble's 1929 observation that galaxies recede proportionally to their distance overturned the static universe model and provided the first concrete proof of cosmic expansion, with a measured Hubble constant of roughly 70 km/s per megaparsec today. This discovery is fundamentally older than #3 Discovery of Exoplanets by more than six decades, establishing the dynamic framework for all modern cosmology. Hubble's law remains a cornerstone, confirming a linear relationship out to over 10 billion light-years, a distance benchmark that no other measurement of its era could achieve.