How did eddwin hubble discover the big bang theory?

Edwin Hubble did not discover the Big Bang theory itself, but his observations laid the groundwork for it. In the 1920s, Hubble discovered that distant galaxies were moving away from us, with their light shifted toward the red end of the spectrum (redshift), indicating that the universe was expanding. This finding led to the formulation of the Big Bang theory, which posits that the universe began from a hot, dense state and has been expanding ever since. Hubble's work fundamentally changed our understanding of cosmology and the origins of the universe.