© Corbis
Every 100,000 years or so, the field flips, meaning that compasses would point south, rather than north. It's been about 780,000 years since the last reversal.
Every 100,000 years or so, the field flips, meaning that compasses would point south, rather than north. It's been about 780,000 years since the last reversal.
Follow the direction of a compass needle and you'll end up at the North Pole, right? Not these days.
The planet's magnetic field is on the move, a normal enough phenomenon, but one that has some rather bizarre implications, such as the need to renumber airport runways.
Tampa International Airport on Florida's west coast just finished renaming its three runways, a laborious project that interrupted airport traffic for a month while runways were shut down for repainting.
"Everything had to be changed," airport spokeswoman Brenda Geoghagan told Discovery News. "It was a huge project."
Tampa's busiest runway was called 18R/36L, a designation indicating the runway is -- or was -- lined up 180 degrees from north when approached from the north and 360 degrees from north when approached from the south. (The letters "R" and "L" differentiate between the airport's two parallel runways.)
