Forty years ago, Liz Keim set up an old Army 16mm projector at theExploratoriumand began showing films to the interactive museum’s patrons. They weren’t the typical science and nature documentaries, but experimental art films meant to challenge what cinema is.

“I was very young, so I didn’t think too much about it holistically,” said Keim, the museum’s director of Cinema Arts and senior curator. “I was really thinking about: Here is this place that does work at the crossroads of the arts and sciences. That’s where a lot of sparks fly. So I wrote up a proposal and then I messed around. The museum was really into prototyping and experimenting. That’s pretty muchthe foundation of how you learn— through mistake making and everything.”

As Keim puts it, it’s been four decades of “minds being blown,” and the program she started has become a source of civic pride — so much so that the mayor’s office is proclaiming Thursday, March 2, as Exploratorium Cinema Arts Day in San Francisco.

“我们是一个城市,一个充满活力和包容的艺术ommunity that I am so proud of, and the Cinema Arts Program at the Exploratorium really fosters that by merging the arts with science, bringing together residents, kids and families, and visitors to experience what our filmmakers can accomplish on the big screen," Mayor London Breed said in a statement to The Chronicle. "Forty years later, we continue to celebrate this immersive experience that inspires future generations of artists to create work that brings people together to explore ideas."

The science, technology and art museum will celebrate in the evening by turning out the lights and transforming the whole facility at Pier 15 into a cinema. “After Dark: Extended Cinemas,” part of the museum’s adults-only Thursday evening series, kicks off a yearlong anniversary celebration with movie-centric events.

“We do ‘After Dark’ every week, and it’s an opportunity to expand cinema,” curator Samuel Sharkland said. “As a process and as a viewing experience and as performance throughout the entire museum, so it’s not inhibited by discrete walls. For this particular ‘After Dark,’ we are exploding movies throughout the entire museum, which is exciting.”

Themes include “Antique TikTok,” super-short films from the 19th century through the 1990s of people just doing stuff (one of the first films to be copyrighted is a guy named Fred sneezing); shorts from a new “You Are Here” series about San Francisco’s Chinatown fromGood Medicine Picture Company;and an opportunity to make an animated film — starring yourself.

Next week,the Exploratoriumplans to team with S.F. Urban Film Fest for“After Dark: Integrating Ecologies,” which will include a screening of the Oscar-nominated documentary “All That Breathes,” about two brothers who devote their lives to saving the black kite, a bird of prey essential to New Delhi’s ecosystem. On April 13, “After Dark: Drawing Sound” brings an immersive program expected to feature a musical and visual performance by local artistsFred FrithandHeike Lissthat explores the nature of improvisation.

April also marks the 10th anniversary of the Exploratorium’s move to the Embarcadero from the Palace of Fine Arts, which hosted the museum from its inception in 1969 to 2013. In the space by the bay, Keim and Sharkland have been able to expand the museum’s cinema palette.

Keim studied fine arts at UC Davis and was in grad school at San Francisco State University as an aspiring filmmaker when she answered a want ad for summer work at the Exploratorium. She found herself in a room with applicants much like herself — and all were interviewed by Exploratorium founder Frank Oppenheimer, a Berkeley physicist and younger brother of fellow Berkeley physicistJ. Robert Oppenheimer,head of the wartime Los Alamos Laboratory that developed the atomic bomb.

“每个人都在蓝色牛仔裤和t恤衫and in their 20s, and then here comes this elderly gentleman dressed in a suit with a tie,” Keim said. “I had no idea who he was, but he came in and we had one of those conversations that just intrigued me. The musing that we did, there was just something about him and I realized I wanted the job.”

She got the job, beginning as a weekend receptionist, and became a protege of Frank Oppenheimer before hedied in 1985at age 72.

Sharkland came to the museum as a student at USF and became Keim’s protege. He’s been at the Exploratorium for 15 years and says he’s energized by the “democratization process that is very important to the Exploratorium ethos.”

“I'm nourished by the ‘aha’ moments that happen again and again,” Sharkland said. “The fact that we have the privilege to kind of crack open people’s minds or perception, even just a little bit, is always rewarding. It’s the same when we host school groups, and to have the privilege to be a core experience for a young person’s first view into alternative cinema and to open up their ideas for the possibility of what film can be.”

Reach G. Allen Johnson:ajohnson@sfchronicle.com; Twitter:@BRFilmsAllen