Public's UFO obsession has experts, others sorting what's fact, what's fiction

"Impact x Nightline" looks at the public's long obsession over UFOs and aliens and speaks with scientists to determine science fact from science fiction.

The stories of flying saucers, little green men, and contact with beings from across the cosmos have fascinated the public for centuries as people have wondered what's beyond our skies.

But over the last few decades, as science and mass media have expanded, the obsession with unidentified flying objects and possible extraterrestrial life has exploded.

From the fun, such as sightseeing tours of supposed UFO activity hotspots like Roswell, New Mexico, to the serious, with last year's tense congressional hearings on the subject, a lot of money, resources and time has been spent answering the question: "Are we alone?"

"There are people who will see things that are explainable, but they can't explain it. So to them, it's unidentified. Fine. Well, let's investigate it," famed astrophysicist Neil deGrasse Tyson told "Impact x Nightline."