I remember a writing course in which we were challenged to create a new character, past and all. Sounds easy enough, and we took turns blurting playful answers to basic attributes. First name, asked the teacher? “Alastair!” someone shouted. Last name? “MacAlastair!” said someone else, laughing.

The laughter died away, though, as it became a challenge to keep the story straight. If Alastair MacAlastair had fought in Vietnam, what was he doing in college today? “Uh … he is trying to rebuild his life after prison.” And why was he in prison? Each new fact created more of a person but also trapped us, eroding our ability to invent — as with life itself, each choice shut off all others, and making no choice is a choice like any other.

I thought of this while watching the new Star Trek movie, which was not Citizen Kane but was a fun day at the show. I especially found it clever that – and I wouldn’t say this if I thought it constituted a “spoiler” – that the writers chose to create an alternative timeline, rebooting the beloved characters but jettisoning all previous canon. Batman and Battlestar Galactica did this recently, and I wouldn’t be surprised if other cult franchises followed suit, as a way out of the corners into which they’ve written themselves.

Even if other sci-fi franchises do reboot, though, it will be interesting to see what new form they might take over the coming decades. Most science fiction tells you much more about the year it was made than the year it predicts; Star Trek may have been set in the 23rd century, but its sets, score, exaggerated play-fighting, heavy-handed social allegory, perky feminine assistants and sexually irresponsible captain looked very much like 1966 Westerns or cop shows. (Relating to the title of this blog, they even used the set of Mayberry, with some tumbleweeds added, for a post-apocalyptic wasteland.)

Similarly, the original Star Wars was wildly popular partly because it hit all the right notes of 1977: young rebellion against the Man, plucky female characters, pseudo-Oriental wisdom — and whole sections of plot and dialogue lifted from Westerns, a genre whose recent demise had left a hole in popular culture. (That scene where Luke realizes his parents are in danger? Lifted line-by-line from The Searchers.) At the same time, it did things no science fiction had ever done: it was fun, had great special effects and presented a dented, lived-in world instead of the usual spires and togas.

Science fiction has done this for a century, extrapolating the burning headlines of the moment and offering earnest writers a soapbox – occasionally resulting in some of humankind’s most thoughtful and imaginative creations. But the whole genre is rooted in changing technology — it couldn’t really exist for most human history, because the future was not radically different than the past. Not coincidentally, it arose as technology began to boom about a century ago, and exploded in popularity in the 1960s as the global energy use curve took a much steeper angle. The more rapidly society changed, the more popular sci-fi became.

But what happens when we begin to slide down the other side of the energy curve? In the next few decades we will not only not see the economy recover to what it was, we might have to rethink what “economy” means. We might experience more natural disasters until we consider them normal. We might see fuel problems increase until more and more people give up trying to get petrol.

I don’t know what kind of future movies, television and YouTube have, as improving technology runs up against decreasing energy and economy. I don’t expect them to vanish in the next few decades, though, although they might be available to fewer people. Science fiction fills the top-grossing movie lists and whole sections of the bookstore, and probably won’t go away as a genre either. But what would it look like? If it predicts a future of small farms and small towns — like, say, Mayberry – is it science fiction anymore?

Until now almost all Hollywood futures have fallen into two types. In Things to Come, Star Trek and 2001: A Space Odyssey, the future is utopian: people are smarter, free of poverty and racism, and living in a magical world of spaceships and domed cities. In Mad Max, Resident Evil, I Am Legend and Terminator, the future is the opposite: a person or small group soldiers on after the Apocalypse has killed nearly everyone, and face an uncertain future.

As John Michael Greer has pointed out, many people believe in these futures as a matter of faith, and they are Christian ideas in science fiction drag. More specifically, they represent the two main strains of apocalyptic Protestantism, called post-millennialist and pre-millennialist to their friends. Post-millennialists tend to believe that the world will progress and improve until we ascend to the heavens, while pre-millennialists tend to believe that the world is going south fast, and that a coming Tribulation will weed out the unworthy. (It’s probably not a coincidence that both strains also arose during the technology boom of the last few centuries, and that pre-boom denominations like Catholic and Lutheran do not fall into either category. )

During the mid-20th century, as energy use skyrocketed exponentially, science fiction was definitely post-millennialist – the world was getting better and better, and we would soon touch the stars. In the 1970s, though, social unrest, oil shocks and recession darkened the global mood, and issues like overpopulation, pollution and the limits to growth percolated into the public consciousness. The pre-millennialist Rapture movement spread rapidly among Baby Boomers, popularizing the imminent end.

Not coincidentally, science fiction got dark, dystopian and pre-millennialist fast – only a decade separates 2001: A Space Odyssey from Mad Max. Star Wars had a few hopeful moments but didn’t predict any future – it happened “a long time ago” – and most of my generation have been raised on 40 years of doom, each new film only boosting the body count.

With one exception: Star Trek. Created at the tail end of the utopian-future era, it has anomalously lingered and flourished even through decades of holocaust porn – perhaps the reason for its famously devoted following in a cynical age. Its vision has been diluted somewhat from Gene Roddenberry’s creation, but it continues to show a world without racism, without poverty, without class, without corporations, without even fashions. I wouldn’t choose Roddenberry’s vision of one-world socialist government to get there myself, but I’m completely behind the ideals.

As the world enters an era far more difficult than the 1970s, science fiction might lunge even further into grim survivalist epics, but – and I’m afraid to even ask this – how much darker and bloodier can they get?

On the other hand, the zeitgeist does not always get darker in a crisis – sometimes, as when World War II began, people pull together in common cause, more hopeful than they would be in a time of hedonism. The Wall Street boom of the 1920s gave us many tragic movies and dystopian futures; only when the Great Depression and World War II began, and the world was plunged into darkness, did people find the future hopeful and holy again. As we enter what may be the greatest crisis, Star Trek’s optimism might have reached right across the decades to again find its moment.

Of course, that optimism assumed that we would be uploaded to the stars soon, and now it seems we won’t. But we can enjoy Lord of the Rings even if we don’t believe there were real elves, and we can benefit from a sanguine vision of a model society even after it has slipped the surly bonds of expectation. We can love it as fantasy, and remember that once long ago, that was what the future was like.