As strange as it sounds, this is something that might (and eventually will) happen -- although facts have been distorted so heavily by conspiracy theorists that geomagnetic reversal ends up sounding like a doomsday scenario.
The Earth's magnetic field, with its north and south poles, isn't as constant as you'd think. During the 20th century, when scientists began studying the Earth's polarity more closely, the exact location of the poles would shift anywhere between 6.2 and 24.9 miles (10 and 40 kilometers) per year. Even more surprising is the fact that sometimes the magnetic poles completely flip -- so the North Pole heads south and the South Pole travels north. This happens very infrequently throughout the Earth's history: The last reversal happened about 780,000 years ago.
So what does this all have to do with 2012? Alarmist Web sites have falsely connected magnetic reversal with a reversal in the rotation of the Earth. Conspiracy theorists also claim that a magnetic reversal is scheduled for 2012 (in most cases, on Dec. 21), and that when it does occur, catastrophic disaster will strike the planet as it starts to spin in the opposite direction.
Experts note, however, that it's not possible to predict exactly when a geomagnetic reversal will happen, and as far as we know, such an event doesn't carry any fatal consequences. Additionally, it's impossible for the Earth to change its rotation.