So, geophysicists have been studying the earth's magnetic field, and they think it's getting ready to "flip" — with the north and south poles changing places.
This has happened a few hundred times in the planet's history, most recently 780,000 years ago. The poles tried to swap places much more recently, 40,000 years ago, but snapped back into place.
The magnetic field is understood to be created by the flows of liquid metal in our planet's core. After studying satellite data, geophysicists now believe that "swirling clusters of molten iron and nickel" are an early sign of an impending pole-flip.
If it happens, when would it take place? No-one knows.
But it'll be a nightmare! As science journalist Alanna Mitchell explains in this Undark excerpt from her book The Spinning Magnet …
The Earth's magnetic field protects our planet from dangerous solar and cosmic rays, like a giant shield. As the poles switch places (or try to), that shield is weakened; scientists estimate that it could waste away to as little as a tenth of its usual force. The shield could be compromised for centuries while the poles move, allowing malevolent radiation closer to the surface of the planet for that whole time. Already, changes within the Earth have weakened the field over the South Atlantic so much that satellites exposed to the resulting radiation have experienced memory failure.
That radiation isn't hitting the surface yet. But at some point, when the magnetic field has dwindled enough, it could be a different story. Daniel Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, one of the world's experts on how cosmic radiation affects the Earth, fears that parts of the planet will become uninhabitable during a reversal. The dangers: devastating streams of particles from the sun, galactic cosmic rays, and enhanced ultraviolet B rays from a radiation-damaged ozone layer, to name just a few of the invisible forces that could harm or kill living creatures.
You may now commence a) ambient, low-level panic, and b) jokes about that craptastic sci-fi flick, The Core.