NASA has its very own doomsday debunker, astrophysicist David Morrison

Swirling with lunacy and paranoia, the theories warn of mayhem and cataclysm. They fill books and websites, inspiring hand-wringing among gullible people. The claim: The world is ending on Friday, the final chapter in an ancient Maya prophecy carved into stone calendars thousands of years ago.

The stories are a jumble, based on everything from New Age mysticism to biblical "end times." In some accounts, a secret giant planet is about to slam into Earth, or a solar storm will wipe out the human race. None has any basis in fact, scientists say, but a poll this summer found 12 percent of Americans are worried. Some teenagers have even talked of suicide.

As Dec. 21, 2012, draws near, however, the U.S. government has a secret weapon to hold back the tidal wave of misinformation and pseudoscientific quackery: a bespectacled 72-year-old scientist, often clad in a rumpled cardigan, sitting in a two-story office building off Hwy. 101 in Mountain View, Calif.

The answer man

David Morrison is Kryptonite for the world's conspiracy craziness. A Harvard-trained astrophysicist who studied under Carl Sagan, Morrison is the senior scientist at the Astrobiology Institute at NASA Ames Research Center. He has worked on many of America's top space missions, from Mariner to Voyager to Galileo, and published more than 155 technical papers and a dozen books on astronomy.

These days he has emerged as NASA's most prominent Debunker of Doomsday, answering questions from people all over the world on his website, giving speeches and talking to the media. While some of his colleagues wonder if he's wasting his time, Morrison holds out hope that reason and facts can win out, even in an age of Internet hoaxes and hype.

"I got my first doomsday question four years ago and wondered what the heck it was," he said. "Perhaps I made the mistake of answering them, but since then I've gotten a little over 2,000 e-mails. I got 200 last weekend."

One of the most common rumors is of a mysterious planet named Nibiru hiding behind the sun, ready to slam into Earth.

"Impossible," Morrison said. "Earth goes around the sun. We see all sides of the sun. We'd see it."

Kamikaze comets or asteroids? The more than 100,000 professional and amateur astronomers around the world would see those, too, years before they got close to us, he said.

Solar flares? Sure, the sun has pulses and storms, which sometimes can disrupt electronics on Earth.

"That's one of the few things here that is real," Morrison said. "We know the sun has an activity cycle every 11 years. The peak is late next spring. There will be flares. But they don't hurt us. This cycle the flares are weaker than last time."

In recent months, Morrison has appeared in Web videos on NASA's site, which he says is getting more clicks on doomsday topics than any issue except the Mars rover mission.

Although many claims are spawned by everything from religious zealotry to hucksters selling books, he said, there is a serious side.

"I get questions from people saying, 'I'm 11 years old, and I can't sleep, I can't eat.' I have had kids saying they are considering suicide, mothers e-mailing me saying they are considering killing their children before the end of times."

Andrew Fraknoi, chairman of the astronomy department at Foothill College in Los Altos Hills, Calif., said Morrison's work is heroic.

"He has taken on a thankless task," said Fraknoi, who also is speaking out to debunk doomsday fears. "He feels that we, as scientists, have an obligation to respond, to reassure the public and to give the public the fact-based view of the universe. That is so absent from so many realms of our social discourse today."

But that doesn't mean they thought the world was going to end, said Rosemary Joyce, a professor of anthropology at University of California-Berkeley.