Arno Penzias is an American physicist who, along with Robert Wilson, co-discovered the cosmic microwave background radiation, a key piece of evidence supporting the Big Bang theory. His work in radio astronomy significantly advanced the understanding of the universe's origins. Penzias's contributions to astrophysics and his research on cosmic background radiation have earned him widespread recognition, including the Nobel Prize in Physics in 1978. His achievements have had a profound impact on the field of cosmology.