Edwin Hubble, an American astronomer, conducted pioneering discoveries in the 1920s that led to the discovery of the universe’s expansion. Hubble used the Mount Wilson Observatory’s 100-inch Hooker telescope to observe a redshift in distant galaxies’ spectral lines. This redshift showed that these galaxies were receding from Earth.
Hubble also discovered a relationship between a galaxy’s distance and its degree of redshift, resulting in Hubble’s Law, which asserts that the more distant a galaxy is, the faster it recedes from us. This gave solid evidence for the universe’s expansion, a key component of the Big Bang theory. His work demonstrated that the world is not static but is constantly expanding, revolutionizing our knowledge of cosmology.