The original "Star Trek" television series premiered 40 years ago today, and actor Leonard Nimoy can barely believe it.

"Can you imagine?" he asks. "It's 40 years. ... Years ago, parents would say to me, 'Oh, my kids love your show.' Now, a lot of kids say to me, 'My folks love your show.' The generation thing has really turned itself upside down."

Nimoy made a mark on science-fiction and television history with his portrayal of Vulcan science officer Mr. Spock, a character whose pointed ears and cold, logical demeanor have become as much a part of American pop culture as "Star Wars" and Barbie dolls.

But, Nimoy says, nobody thought "Trek" would become a phenomenon in the early days, especially since ratings for the show were mediocre, leading NBC to cancel it after just three seasons.

"It was a struggle," he says. "I thought we were doing some good and interesting work, but it was a struggle. ... I don't like to point a finger, but I don't think the network really understood what they had."

The original series was short-lived, but "Star Trek" gained popularity in reruns and eventually built a following that spawned five spin-off television series and 10 feature films. Nimoy says he is pleased with the show's legacy.

"It's all about trying to make the world and the universe a better place," he says. "I'm proud to be connected with it. I think we need that in our lives. We need ethical, heroic people trying to do the right thing to help others and to improve life on this planet and in the universe."

Indeed, many themes in "Star Trek" involve people making difficult choices for the benefit of all living things. And the original series was notably progressive for the 1960s.

"There was the first interracial kiss," Nimoy says. "There were stories about overpopulation. There were stories about global warming, stories about planet conservation, stories about ethnic wars, all the things that we're still dealing with."

Even with 40 years of "Star Trek" behind us, the series is poised to move boldly into the future. There's talk of a movie directed by "Lost" creator J.J. Abrams.

"The story that I've heard bandied about is an idea that's been floating around for some time," Nimoy says. "The idea of going back to academy days, where Spock and Kirk first meet."

Nimoy says his agency received a courtesy call from Paramount Pictures indicating that the studio is going forward with a new film, but he doesn't know if he or William Shatner, who originated the role of Capt. James T. Kirk, will be involved in the project.

In the meantime, Nimoy, who is 75, is making the rounds at conventions in celebration of the series' 40th anniversary. He appeared in Las Vegas in August and in Toronto last weekend, and visits Chicago and Sacramento today through Sunday.

"It's kind of like taking a victory lap," Nimoy says. "You show up and everybody's happy to see you."