On November 20, 1889, astronomer Edwin Hubble was born in Marshfield, Missouri. Hubble's work revolutionized our understanding of the universe and laid the foundation for modern cosmology.

In the 1920s, while working at the Mount Wilson Observatory in California, Hubble made groundbreaking discoveries using the observatory's Hooker Telescope, which was the largest telescope in the world at the time. He observed that the Andromeda Nebula was actually a separate galaxy from our own Milky Way, proving the existence of galaxies beyond our own. This discovery expanded the known size of the universe immensely.

Hubble continued to study galaxies and made another remarkable discovery: he noticed that the galaxies appeared to be moving away from Earth, and the farther away they were, the faster they seemed to be moving. This observation led to the formulation of Hubble's Law, which states that the universe is expanding uniformly.

The idea of an expanding universe supported the Big Bang theory, proposed by Georges Lemaître, which suggests that the universe began from an initial point and has been expanding ever since. Hubble's observations provided the first observational evidence for the Big Bang theory, which has since become the prevailing cosmological model.

The Hubble Space Telescope, named in Edwin Hubble's honor, was launched into orbit in 1990 and has been providing stunning images and invaluable data about the cosmos ever since, enabling astronomers to study distant galaxies, planets, and celestial objects in unprecedented detail.

Edwin Hubble's birthday, November 20, is a significant date in the history of science, as it marks the birth of a pioneering astronomer whose work transformed our understanding of the universe and our place within it.