Part of the show New Planets, Harmonics and the science of Sound.
Chris in Kentucky asked:
How long would a flip in the Earth's magnetic field take, and how might it affect technology?
We don't really understand the Earth's magnetic field. We think it's produced by something to do with lots of molten iron flying around in the Earth's core. It's really difficult to model and on average it seems to flip about every quarter of a million years. It's been a million years since the last one flipped, so we think we're probably about due for one. This magnetic field does all sorts of things. It protects the atmosphere from the solar wind which is lots of particles being thrown off from the sun. They get caught by the magnetic field and get thrown off to the North and South Poles. This is what causes the Aurora Borealis or the Northern Lights. If the Earth's magnetic field flipped, it would probably almost disappear and start changing round, so we'd all get Northern Lights. It would have some negative effects though. It might have some effects on the climate because it would heat up the top of the Earth's atmosphere and it would do things like stop radio communications.