The name of the theory that explains the origin of the universe is the Big Bang Theory. This widely accepted scientific explanation posits that the universe began approximately 13.8 billion years ago from an extremely hot and dense state and has since been expanding. As the universe expanded, it cooled, allowing matter to form and eventually giving rise to galaxies, stars, and planets. Evidence supporting the Big Bang Theory includes cosmic microwave background radiation and the observed redshift of distant galaxies, which indicates they are moving away from us. This theory has profoundly impacted our understanding of cosmology and the universe's evolution.