Cosmos: A Personal Voyage (1980)

Carl Sagan's 13-part PBS series remains the most-watched science documentary ever, reaching over 500 million viewers worldwide. It seamlessly wove astrophysics, biology, and philosophy into a poetic narrative that made the universe feel accessible, igniting a generation's passion for science. This series outperforms #2 in cultural impact and longevity, inspiring decades of public engagement with astronomy. With only a $8 million budget, it achieved a cost-effectiveness unmatched by modern blockbuster documentaries.