The Wall is one of the biggest mysteries in all of Game of Thrones. At 700 feet tall and spanning 300 miles across the northern border of Westeros, it's made entirely of ice and has stood at the same height for 8,000 years since the end of a legendarily lengthy winter known as the Long Night. But how? Even in the cold climate of the North, ice melts.

Most Westerosi would say it's magic that keeps the Wall up. But at the beginning of the series so many seasons ago, Luwin—a member of Westeros's scholarly class, the maesters—tells young Bran Stark that magic is gone. "Maybe magic once was a mighty force in the world," Luwin admits. "But not anymore." Luwin effectively concedes that even the maesters have no idea if magic ever existed. Even if you believe the theory that there's a vast maester conspiracy against magic, this complicates things.

But since then, we've seen dragons and shadow babies, men who can change their faces and possess the bodies of wolves—and we know some of those have been around for a long, long time. So what gives? One fan theorist, a vlogger named Preston Jacobs, has a sort of sideways answer: It's not magic. It's science.

It's not entirely a crazy idea. Before A Game of Thrones took off and the Song of Ice and Fire series became his life's work, George R.R. Martin was known primarily as a science fiction writer. And in science fiction, unlike in love and war, there are rules—laws, to be exact. Three of the most famous of these laws were written by Arthur C. Clarke, a genre titan who you may know as the author of 2001: A Space Odyssey. In what is now called Clarke's Third Law, he states: "Any sufficiently advanced technology is indistinguishable from magic."

Let's go back to the Wall, a prime example in the case of Game of Thrones. Maybe there is some sort of magic keeping it up. "Or maybe," Jacobs suggests, "there's some sort of refrigeration unit."

HBO

It seems farfetched, until you start digging deeper—and Jacobs, an auditor for the U.S. State Department by day, is an expert at doing just that. After re-reading the series a couple of years ago, he jumped right into reading the vast majority of Martin's extant works, including every story that's taken place in the author's most frequently visited setting, a shared universe called the Thousand Worlds.

Look closely enough at the stories in the Thousand Worlds (many of which are out of print) and you start to see a whole lot of similarities between them and the Song of Ice and Fire series in theme, character, and plot alike. "One of the reasons I think Ice and Fire is so rich is he's been stealing all of his best ideas from his stories and just plopping them in there," says Jacobs. "'In the House of the Worm' stars Jaime, essentially. It's basically the same character."

It turns out that "In the House of the Worm" is actually a good place to start when explaining how Game of Thrones is really science fiction. More specifically, it's post-apocalyptic science fiction. "In the House of the Worm" takes place on a world in the midst of something Martin calls an interregnum—a period of time in which a civilization that was once capable of spaceflight is recovering from a catastrophic event that sent it back to a more primitive state. These societies are haunted by relics of a more advanced past, yet stuck in a medieval rut, unable to replicate the technology that led to their eventual regression. Sound familiar?

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In Westeros and its counterpart Essos, characters marvel over wonders like the Wall, the impregnable Eyrie, and the massive Titan of Braavos—constructs that these cultures would never be able to build in the present. But doesn't civilization usually progress, not regress? The best example of a real-world society that was supposedly inferior to its predecessor is, admittedly, medieval Europe after the fall of Rome, a pretty good analogue for Westeros. But one thousand years after Rome fell, medieval Europe was in the thick of the Renaissance, a period filled with great artists, thinkers, and inventors. Eight thousand years after the Long Night, that sort of progress seems to have evaded Westeros and Essos both.

The Long Night itself seems to hint at the explanation for how this world—as Jacobs and other theorists do, let's call it Planetos—became the way it was. A winter that lasts for a generation seems pretty hard to believe, even in a world with seasons as crazy as those on Planetos. In the first season of Game of Thrones, Tyrion discusses with Maester Aemon and Lord Commander Mormont the longest winter he'd ever lived through, and mentions it lasted three years. But as Jacobs points out, there is such a thing as a generation-long winter in the real world: a nuclear winter.

In the Thousand Worlds universe, humanity is at perpetual war with multiple hive-minded species—a form of life that pops up in A Song of Ice and Fire as well, and which Jacobs explores in detail in one of his theories. During this endless war, the hive-minded races typically destroy human worlds using nuclear weapons, wait a hundred years for the dust to settle, and then invade and enslave the survivors. And in the interim, something familiar happens, as it does on High Kavalaan, a planet in Martin's first novel, Dying of the Light.

"I think the book that really made me think Westeros could be post-apocalyptic was Dying of the Light," says Jacobs. "When he started writing about nuking people, with everybody hiding in mines and founding their own houses and holdfasts, it just occurred to me that the Long Night could be a nuclear winter."

Mines, like the mines under the Lannisters' ancestral home of Casterly Rock, would certainly serve as effective fallout shelters. As would the crypts beneath Winterfell and the tunnels beneath the Red Keep in King's Landing, among dozens of other subterranean structures in Martin's book series that have yet to make it to the show.

Another hallmark of Martin's Thousand Worlds stories are biological weapons, which humans use in battle against their hive-minded foes. With them, they can manipulate genes in order to create almost anything—including dragons, people who can change their skin, and people who can animate dead bodies. The scientists who developed these weapons were part of a group called the Ecological Engineering Corps. Their symbol? A theta, just like the one Sansa Stark wears on a necklace starting at the end of Season Four.

HBO

Of course, Martin has adamantly denied that A Song of Ice and Fire is related to his previous works. But then again, his adaptors have also adamantly denied that Jon Snow is coming back. It nearly always behooves creators to keep mum on the big secrets that explain how their creations tick.

But would Martin really reveal to readers that the entire world in which they've been invested for five books and seasons is fundamentally different in genre from the series they thought they were reading and watching? Jacobs thinks probably not—at least not as dramatically as has been done in, say, Planet of the Apes. Instead, he imagines an ending that will satisfy the fantasy lovers, but rewards Martin's devoted and observant sci-fi fans as well.

"If I were going to end the story, I would end it with Sansa traveling by boat to the Isle of Faces," says Jacobs, referring to an island of mythical importance in the book series filled with Weirwood trees. "Perhaps she'll join the Weirwood net, like Bran, to take care of everything and save everything. And—you know how in Blade Runner they didn't really reveal that Harrison Ford was a replicant until ten years later in the director's cut, it was so subtle? It may be like that, where Sansa passes by one piece of technology on the way to her final scene. You miss it for a second, and then you see it. Maybe it's a buried spaceship."

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