10. Changes in the Sun's magnetic field will lead to powerful flares.

The bottom line is that no dragon's breath of flame will stretch across 100 million miles of space and blowtorch Earth. The largest solar flare recorded to date, on Nov. 4, 2003, spewed several billions of tons of plasma in Earth's direction. The flare's X-ray radiation that impacted our protective atmosphere had the equivalent radiation of 5,000 suns.

4. An asteroid will smash into Earth. A threatening near-Earth asteroid that's gotten the most press is the 900-foot wide Apophis. But its chances of collision have been downgraded to 1 in 250,000 at its next close approach in 2029. In theory, an uncharted asteroid or comet could come out of the blue tomorrow. But if we don't know about it today, the Mayans certainly didn't know about it 1,200 years ago. Earth-killer impacts are tens of millions of years apart. So there's no reason to be a doomsday clock-watcher.