Another holiday season and another year has gone by in which  Star Trek is still one of the most relevant pop culture institutions of all time. Despite the original series lasting only three seasons, the franchise still holds strong 50 years later. And William Shatner, the original Captain Kirk, thinks he knows why.

Speaking with Paradethe legendary actor boils it down to the public's love of science fiction, and the timeless questions the genre raises.

"Star Trek is science fiction, and science fiction, to a large group of people, is part of the awe and wonder of the universe," Shatner said. "We speculate about what’s out there, and since we have no way of knowing, anyone’s speculation is as valid as anybody else’s. But it is of interest to people who look at the stars at night and wonder what’s out there and whether little green men are flying this way."

RELATED: Star Trek: Discovery Faces Catastrophe, and Section 31, in New Trailer

Shatner added that the way science fiction confronts life and death adds to the fascination. "Could we possibly see life? That brings up the question of death and all the stuff that we have no answers for," he said. "Science fiction speculates an answer, and that, I think, is the fascination."

He also spoke about his Christmas album, his memoir, new film projects, and Star Trek: Discovery. When asked whether he watches the new series, Shatner confessed he doesn't, nor does he watch anything Trek-related, beyond his own work.

Aside from Discovery, which returns in January for its second season, the franchise has in development a sequel to The Next Generation starring Patrick Stewart, and a new animated series, Lower Decks.

RELATED: Star Trek's William Shatner Releases First Track From Christmas Album