When xkcd creator Randall Munroe first posted a new installment of his webcomic titled "Time" on March 25, it looked deceptively simple: a picture of two black and white stick figures, a man and a woman, sitting wordlessly on the ground. There was no story, no punchline, no words. 30 minutes later, the image changed; the figures shifted slightly. And they continued to change every half-hour for the next week–and every hour for months after that–slowly coalescing into a story as the two characters discovered disturbing changes in the landscape around them, and set out on an epic, time-lapsed journey to discover the truth about what was happening to their world.

Readers set out on a similar journey, although their path led not to the wild unknown, but rather back to the same URL where the mystery continued to unfold hour by hour. Who were these characters? Where were they? What did the story mean? Munroe offered no direct answers, instead seeding the panels with esoteric clues from botany, astronomy and geology. Soon, "Time" had developed a fanatical following that pored over every update pixel by pixel and gathered online to trade theories, decipher clues, and even write songs.

The obsessive devotees of the comic-within-a-comic created a discussion thread that exceeded 1,300 pages, a "Time"-specific wiki, and even a glossary of the lexicon they invented to describe the world of “Time” and their experiences with it. While they refer to Munroe simply as "OTA" (the One True Author), a "newpic" (plural: "newpix") is defined as the unit of time that elapses between updates, also known as "outsider minutes." True to its name, "Time"–where a single step could last an hour, and a night could span multiple real-life days–took on its own internal sense of chronological speed: glacially slow for animation, but imbued with a continual sense of motion that felt utterly unique for a comic.

After more than four months of hourly updates, the journey finally came to an end last week, and the final product is 3,099 panels long–so long that the Youtube video compiling them (above) runs more than 40 minutes from start to finish. Even better, Munroe is finally talking about the elaborate backstory behind the minimalistic and seemingly ancient world of "Time," which he reveals was set not in the past, but 11,000 years in the future.

"In my comic, our civilization is long gone. Every civilization with written records has existed for less than 5,000 years; it seems optimistic to hope that the current one will last for 10,000 more," Munroe told WIRED. "And as astronomer Fred Hoyle has pointed out, since we've stripped away the easily-accessed fossil fuels, whatever civilization comes along next won't be able to jump-start an industrial revolution the way we did."

Although the comic takes place many millennia in the future, its setting is modeled on a geological event that took place more than 5 million years ago, when tectonic activity sealed off the Mediterranean Sea from the Atlantic Ocean, causing the sea to evaporate and leave a basin of dry land two miles below sea level. In Munroe's comic, the same geologic shifts have reoccured in the distant future, and that's where we find the characters when the comic opens: in the bottom of the desiccated Mediterranean Sea, building castles out of sand.

The comic also teeters on the cusp of another ancient (but potentially futuristic) occurrence: the moment when the ocean flooded back into the basin and refilled the Mediterranean Sea, a catastrophic event known as the Zanclean flood. Munroe described the deluge as "100,000 times the size of Niagara Falls. It's only hinted at in the comic, but for geology geeks out there, the trigger was probably an expanded El Arraiche ‘mud volcano’ outflow. Humans most likely helped it along–a Gibraltar Dam is a project that would appeal to engineers anywhere."

Geographically, the comic takes place in the part of the basin between Africa and Europe, so Munroe researched and illustrated very specific plants and wildlife to offer readers hints about the location. “I got suggestions from botanists and herpetologists, and I had a file with details on every species the characters encountered or talked about, like dwarf palms, juniper trees, horned vipers, and sand boas.”

Image: Panel 2,400 of "Time" by Randall Munroe

More clues lay not only within the world, but above it. Astronomically-savvy readers finally got a chance to nail down the time period of the comic during a striking sequence later in the series where the night sky slowly rotated over the characters, revealing a distinctly different configuration of stars than our present sky.

"The Earth's axis wobbles over the millennia, and some individual stars move visibly, so I used a few different pieces of astronomy software–with a lot of hand correction and tweaking–to render the future night sky," said Munroe. He also consulted with astronomer and science blogger Phil Plait and learned that while most visible stars would still be around 11,000 years in the future, the red supergiant star Antares could go supernova and vanish from the starfield.

“When the Sun sets in the night sequence, one of the first things you see is the gap where Antares should be, which was the first clue that this is taking place in the far future,” said Munroe. “Later in the night–which lasted for several days of real time–more astronomical details let readers pin down the date more precisely.”

Even now, some mysteries remain. With the help of a linguist, Munroe invented a language and orthography (dubbed "Beanish" by readers) for one of the foreign cultures his characters encounter, which he wanted to be “as different from [English] as our language is from Linear A,” the still-undeciphered writing system of ancient Crete. His abstruse approach worked; despite the efforts of "Time" superfans, no one has been able to decode the language, which Munroe finds fitting since "we haven't cracked Linear A, either!"

Still, Munroe says that artifacts of the sprawling world he created in the space of a single panel might someday make their way into his other work: "Maybe I'll find a way to sneak a bit more of the language into another xkcd comic."

Now that the story is over, new readers can still go back and navigate the comic frame by frame or view it as a video, although the experience of deciphering its mysteries in real-time alongside a community of equally devoted fans seems impossible to duplicate. And that's what makes "Time" so fascinating: not just the meticulous, interdisciplinary details of its backstory, or the community that formed around it, but the way the comic felt embedded with the experience of time itself, and perhaps equally ephemeral.

Correction 11:05 AM EST 8/2/2013: The number of panels in the completed comic is 3,099, not 3,990.

Correction 10:00 AM EST 8/6/2013: Linear A remains an undeciphered writing system, while Linear B has been deciphered.