What if an ancient civilization could have predicted the future? And calculated the end of time?
Some people say the Mayans, who thrived thousands of years ago in what is now Mexico and Central America, did just that.
The ancient Mayan calendar, say so-called "2012'ers," explains that time itself began about Aug. 11, 3114 B.C. and will end Dec. 21, 2012 -- the winter solstice.
"I believe the Mayan calendar was based on some good astronomy," Lawrence Joseph, author of "Apocalypse 2012," told ABC News. "They had a sense of timing. What I believe about the Maya was they were really good at knowing when. They weren't so good at saying what's going to happen."
Watch the full story tonight on "Nightline" at 11:35 p.m.
Joseph imagines a doomsday scenario not unlike a Hollywood movie due out this month: "The Road," based on Cormac McCarthy's Pulitzer Prize-winning novel.
A trailer for the movie sets the scene: "It is cold and getting colder as the world slowly dies. No animals have survived. And the crops are long gone."
McCarthy is vague about what caused his apocalypse.
But Joseph believes ours will come from solar flares -- bursts of radiation from the sun that will apparently peak at the end of 2012, penetrating the Earth's magnetic field and scorching the electrical grid.
"Over 130 million people in the United States alone could be without electricity for months or years," said Joseph. "And that just doesn't mean no telecom. It means no water, because the pumps are electric. It means no gasoline because the pumps are electric. No refrigeration."
Joseph said it "absolutely is very difficult" to live with the notion that everything we enjoy in the modern world could come to an end.
"I make jokes," he said. "I whistle in the dark. I have two young kids. And life has been good to me."
What does any of this have to do with the Mayan calendar?
"I don't know," said Joseph. "It is a coincidence that is striking and perhaps it's significant."
John Major Jenkins, author of "The 2012 Story," explained the calendar.
"December 21 of 2012 is the last day of the 13 cycles of this calendar, called the Long Count," Jenkins said. "And this calendar was invented about 2,100 years ago in Southern Mexico."
In search of answers, ABC News headed to southern Mexico, and then deep into the Central American jungle, to a place where it's easy to imagine a flood lasting 40 days and 40 nights. We searched for clues amid the ruins of the ancient Mayans.
Our guide was archaeologist Christopher Powell, who helped with some of the most important excavations of a civilization that mysteriously vanished more than 1,000 years ago.
"I consider it a great mystery, and one that I'm willing to see out with an open eye," Powell said.
The Rosetta Stone for 2012'ers is something called the Tortuguero Monument No. 6, a collection of hieroglyphics unearthed in the 1960s and promptly scattered to the four corners of the globe.
One fragment is kept in the bowels of New York's Metropolitan Museum. The museum would not allow us to film it.
A good chunk of it is in the Carlos Pellicer Museum in Villahermosa, Mexico. When we visited, the museum was closed due to flood damage.
The two remaining fragments have been missing for decades. Last photographed over 40 years ago, these two pieces are the key to unlocking the secrets of Tortuguero Monument No. 6, experts say.