- Earth's magnetic field is carting away toward Russia at a rate of about 40 miles a year.
- The shift widens the distance between true north and magnetic north, which is the direction a compass needle points.
- The phenomenon is normal, though it does have implications for modern life.
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.)