Image: ESA/ATG Medialab
It’s not something that’s ever happened in human history so it’s not something we think about too often, but Earth’s magnetic poles flip on a regular basis—at least, a regular basis on a geologic scale. And every time the poles flip, the magnetic field that shields our planet from deadly cosmic rays also flips. The next flip, according to new data collected by the European Space Agency, is coming up sooner than scientists expected.
Earth's magnetic field is rooted deep inside the planet. The solid inner core, which is about two-thirds the size of the Moon, is made primarily of iron and is super-heated to almost 10,300 degrees Fahrenheit. Surrounding this solid core is a thick layer made up of iron, nickel, and small amounts of other metals in a liquid state. Differences in temperature, pressure, and the composition of the outer, liquid core causes convection, and as these metals flow, they generate electric currents that in turn produce magnetic fields. Because the Earth is spinning on its axis, these magnetic fields align to form one giant magnetic field that envelops the planet.
But the polarity of this massive magnetic field isn’t constant. Over the last 20 million years the Earth has settled into a pattern wherein the poles change polarity every 200,000 to 300,000 years; magnetic north becomes south and vice versa. It’s neither a fast nor a clean process. A flip actually takes hundreds of thousands of years, and over the course of that time the magnetic fields tug at one another, with magnetic poles emerging at odd latitudes.
It’s by measuring the variations in the magnetic field that scientists find indications that a polar flip is imminent. ESA’s Swarm mission is a magnetic field mission that uses an array of three satellites to unravel the mysteries of the Earth’s magnetic field.
Recently, big weak spots in the magnetic field more than 370,000 miles above the planet's surface have sprung up over the Western Hemisphere. Meanwhile, the magnetic field has strengthened in other areas, like over the southern Indian Ocean. Scientists behind the Swarm missions aren't entirely sure why the magnetic field is weakening in certain spots, but the likeliest explanation is that the poles are getting ready to flip. So far, it looks like the poles are just starting to migrate a little bit.
Rune Floberghagen, ESA's Swarm mission manager, says the satellites’ data points to the magnetic north pole moving towards Siberia. He also notes that the magnetic field is weakening faster now than it has previously. Scientists estimate that it used to weaken at about five percent per century, but recent data says its weakening by five percent per decade. A full flip might happen in about 2,000 years, far sooner than previously predicted.
So the big question is: what will the flipping magnetic field mean for who or whatever is living on Earth when it happens? It turns out not much. Scientists have found no correlation between past polarity flips and mass extinctions. If anything, power grids and communication systems would face the highest risk when the flip happens.
Since it’s not going to happen anytime soon or do much of anything, we can continue not thinking or worrying about the flipping magnetic field. For the time being, ESA scientists behind the Swarm mission are most interested in using the data they gather to make systems that rely on our magnetic field more accurate, and possibly apply a better understanding of the changing magnetic field to identifying shifting continental plates and predicting earthquakes.