The idea of creatures from another planet is part of our culture, from the warnings of the alien in “The Day the Earth Stood Still,” to the plaintive desire to return home in “E. T. the Extra-Terrestrial,” to the hulking creature of “Nope.” Aliens appear in movies, books, comics, you name it. But are they more than science fiction? And if they were, how would scientists prove it?

The government has investigated reports of alien sightings, including in Project Blue Book, which ran from 1947 to 1969. And last summer, congressional hearings into Navy pilots’ sightings of Unidentified Anomalous Phenomena (UAPs) brought the search for intelligent life back into the public eye. But there’s more to the search for alien life than people spotting lights in the sky. Projects such as Breakthrough Listen are surveying the stars for signals. Advanced telescopes such as JWST are enabling us to collect data on the atmospheres of exoplanets, a first step in detecting biosignatures on distant worlds. And astrobiology projects such as the Mars 2020 Perseverance rover mission are looking for signs of ancient life elsewhere in our own solar system.

Dr. Adam Frank, a professor of astrophysics at the University of Rochester and author of The Little Book of Aliens, joins hosts Ira Flatow and Kathleen Davis to talk about the evidence for life elsewhere in the universe, and how scientists might go about trying to answer the question of whether we’re alone.

Transcripts for each segment will be available after the show airs on sciencefriday.com.

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