In the film, Stephen Hawking's Favourite Places, the world-renowned expert on practically anything space-related, takes a tour across the cosmos on his spacecraft, the SS Hawking.
During a hypothetical flyby over a planet 16 light years away —a very, very long time — Hawking warns humans not to interact with any alien civilization, if one was discovered.
"One day we might receive a signal from a planet like Gliese 832c, but we should be wary of answering back," Hawking says in the movie.
"They will be vastly more powerful and may not see us as any more valuable than we see bacteria."
Hawing has been quoted telling reporters:
"As I get older I am more convinced than ever that we are not alone. After a lifetime of wondering, I am helping lead a new global effort to find out."
Stephen Hawking is also involved in another project, the Breakthrough Initiatives Listen project, which scans the nearest million stars for any signs of life.
At the launch of the project last year, Hawking suggested that any civilization reading human messages could be billions of years more advanced than the human race.