The narcotic effects of sleeplessness — or " hypnagogic reveries " — have long been known to humankind. Members of the Shoshone tribe of Wyoming have traditionally endured ritualistic sleep deprivation to commune with the spiritual world. Ancient Celtic tribesmen underwent self-imposed insomnia to converse with their ancestors. And once a year here in Boston, 600 people gather at the Coolidge Corner Movie Theatre to ply themselves with coffee and Kool-Aid and watch a seemingly endless parade of mind-controlling robots, city-stomping lizards, little green men, and flesh-eating insects — not all of them on the screen.

As a tradition, the annual Boston Science Fiction Film Festival could hardly be described as ancient. Even so, in the 28 years it’s been running, the festival has built an almost alarmingly devoted following — especially when you consider the feat of endurance involved: 24 straight hours of movies with titles like It Came From Outer Space and When Worlds Collide. " My friends all think it must be torture, " says Boston University employee Suzzanne Ochoa, 34, who’s been attending the sci-fi marathon since 1988. " But it’s not torture at all. It’s wonderful. "

Indeed, for many attendees at this year’s festival — SF/28, held over Presidents’ Day weekend — the very idea of staying awake for 24 hours, or at least trying to, is part of the attraction. " That’s the high, the lack of sleep, " says Ochoa, " that euphoric denial that you go through. It makes the movies all the more beautiful, more surreal. " Cambridge resident Robert Noyes, 28, remembers watching a 6 a.m. screening of the Japanese flying-monster epic Rodan — 18 hours into the marathon — and " staring at 25 glorious minutes of nothing but the wanton destruction of many, many miniatures, and thinking, in my sleep-deprived state, that it was the coolest thing I’ve ever seen. "

There are those, though, upon whom the lack of sleep has more troubling effects. " My head hurts just thinking about it, " says Bob Seitz, 49, a vintner from Oregon who’s on his 26th marathon. " You walk outside and you look around every corner. You’re looking on top of the buildings [for aliens]. You’re neurotic. "

When I learn that I’ll be attending SF/28, my first reaction is one of apprehension, followed by dread, and then a kind of grim resolve. And it’s not just the fact that I am far from being a sci-fi fan that bothers me. Even though the event’s organizer, Garen Daly, calls it " the biggest slumber party that ever existed, " you have to assume — given the ray guns zapping, the saucers spinning, the bloodcurdling screams ringing out, and the ravages an ass will suffer from 24 hours in a movie seat — that slumber will be a rare commodity, even for those who seek it. And then there’s the, um, air-quality issue. As one veteran puts it, " It gets smelly. "

The schedule alone is daunting: 14 movies of varying degrees of quality — the good, the bad, and the schlocky — with a 10-minute break after each film. According to the festival program, at 10:30 p.m. we’ll watch The Valley of Gwangi, in which cowboys do battle with dinosaurs; six hours later, we’ll get The Brain from Planet Arous, whose protagonist is " a giant, flying, sex-starved alien brain. " Even the addition of such classics as Metropolis cannot mitigate the fact that, come 1:30 a.m., we’ll be feasting our bleary eyes on the rubbery special effects of Sh! Octopus. The event is, as Daly says, " Something that’s out of the range of what normal people will do. "

Which leads us to a question: what kinds of people, exactly, do do this?

There is a common conception among non-sci-fi fans that the genre attracts the pocket-protector set, thick-spectacled, anorak-wearing misfits who entertain the idea that Jar Jar Binks is a real-life being. While some in the sci-fi community acknowledge and even celebrate their place " on the freaky side of the barometer, " as Ochoa puts it, others are rankled by such characterizations. In the days before SF/28, I receive an e-mail from Dan Kimmel, 47, a movie critic for the Worcester Telegram & Gazette, who is on his 23rd marathon. " I hope this will be a story about a lot of really nice people who enjoy something unusual, " he writes, " as opposed to a ‘get a load of the geeks’ piece. "

Later, Kimmel continues the theme. " The people who come to this thing are not the stereotypical overweight teens with Spock ears, " he says. " These are not people living in their parents’ rec room. It attracts an intellectual crowd. " The critic does go on to add, however, that this year he’ll be sitting with members of the Martian Liberation Organization (MLO), a group of sci-fi buffs who wear quasi-military outfits (jumpsuits, red berets) and who once hijacked the festival because of what they perceived as " an anti-Martian bias. "

The MLO isn’t the only organized group that regularly attends the marathon. The Asteroid Farmers of Saturn are usually well represented, as are the Inner Four Planets You Can Stand On, the Bee People, and the Keepers of the Lost Ark. And while there may not be an abundance of Spock ears or prosthetic foreheads in the audience, there are alien-mating-call contests, paper-airplane-making contests, and frequent mentions of " The Starship Coolidge Corner. " And of course, as Daly says, " Everyone’s got a ray gun. "

Daly, who’s been involved in the marathon since 1978 and running it since 1986, allows that the event attracts its share of " under-socialized nerds. " But even he gets a little touchy at the mention of the G-word. " There are some incredibly smart, accomplished human beings at the festival, " he says. " We have someone who works for the state government, people in the movie industry, several critics, people who own their own companies. We have a guy who is ex-CIA, who did Special Ops in Vietnam. "

Even so, despite the efforts of people like Dan Kimmel to distinguish themselves from Star Trek fanatics, there’s no getting away from the fact that there is something at least a little geeky about a bunch of middle-aged professionals zapping each other with ray guns and hollering, " Duck Rogers in the 24th and a half century! " Indeed, there are those who readily admit this, who scoff at efforts to downplay the dork aspect. " I am especially amused by the Marathoids who look down on Trekkies as geeks, " says Robert Viagas, 46, an editor for Playbill. " I suppose that in the land of the blind, the one-eyed man is cool. "

One thing that’s very clear is that the marathon people are a committed lot. They come from all over the country to attend the festival. They organize vacations around it, miss birthdays and anniversaries. And they start looking forward to it months in advance. " I visit the [festival] Web site starting in August, " says Viagas, " and, I’m embarrassed to admit, send in my ticket money on the Friday before Thanksgiving and start packing the day after Christmas. " He adds: " I have been to 25 marathons, never missing one, whether for job changes, illness, weather, the birth of my two children, or anything else. "

Still, as far as mania goes, Viagas is a moderate. There are those who start getting jittery about the next festival as soon as the lights go up on the current one, for whom a kind of depression sets in when the final credits roll. " It’s just the most disheartening feeling when the doors open and the sun comes flooding in, " says Suzzanne Ochoa. " I’m so sad. All I can think about at that moment is that I can’t wait for next year. "

Ochoa’s not alone. All year long, a message board devoted to the festival hums with event-related chatter: snack-food tips, anecdotes, discussions on such topics as the aerodynamic superiority of the flying saucer over the rocket ship. But in the weeks before the marathon, the tone on the board takes on an almost frantic tone. " It has started. I am deep in the throes of marathon fever, " writes a man named Frank Urbano, a week before SF/28. " I check the website way too often now, upset that there is not a new posting every ten minutes. Counting down the days, hours, minutes. I have butterflies in my stomach. "

Urbano, 47, who owns a local comic-book store, is on his 25th marathon. He generally shows up at the theater the night before the event, braving more than 12 hours in freezing temperatures to ensure he gets a prized front-row seat. " I love it, " he says. " It’s my Christmas. Some of us are pushing for a marathon at the midpoint, to tide us over until the next one. "

Then there’s Harvey Schwartz, a 54-year-old Boston-based attorney who has not missed a single marathon in 28 years, and who has actually suffered domestic strife as a result of his devotion to the event. " One year my wife got so suspicious about me disappearing for a full night every year, she bought a ticket and showed up in a wig to see if I was really where I said I was, " he recalls. " I was so wrapped up in the films that I didn’t recognize her when she sat next to me and put her hand on my knee. I kept on firing my ray gun and she left. "

In the intervening years, Schwartz’s wife has learned to live with her husband’s intergalactic journeys — she’s had to. " I wouldn’t miss this event for just about anything, " he says. " Once a year I get to visit another world. It’s a reminder that there are other realities out there — not so much what’s in the films, but who’s in the theater. These are people who march to a different drummer than the people I meet in my law practice. " Indeed, many of Schwartz’s colleagues have difficulty coming to terms with his fantasy life. " They don’t seem to understand it, " he says, " especially as I have a major federal civil-rights trial the day after this year’s marathon. I told the judge’s clerk I’ll be a little tired on the first day. I set my priorities on this one. "

To put it mildly, Schwartz is a lover of sci-fi films, as are all the festival attendees. On some level, they attend the event religiously because it has become a tradition, a social scene. But it’s an ongoing fascination with worlds other than our own — an urge to escape the drudgery of the everyday — that really keeps them coming back for more. " The marathon isn’t a form of escapism, " Schwartz says, " it’s escapism personified. For 24 hours you’re away from everything else in life. It’s a vacation. "

Others, meanwhile, simply enjoy the flashing lights. " I like visions of the future, " says Rob Noyes. " I like fantastic planet scapes, I like Flash Gordon noises and machines that spark and go brzzzzzt and have no scientific purpose whatsoever except to look cool. I like tales of future dystopia, and I like giant monsters stomping the heck out of cities. Perhaps I’m easily amused. "