Photograph by NASA
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Earth, as seen by the Apollo 17 crew during their mission to the moon in 1972. This flight marked the first time an Apollo trajectory made it possible to photograph the southern polar ice cap.

Photograph by NASA

No, We're Not All Doomed by Earth's Magnetic Field Flip

A geomagnetic apocalypse may not be on the horizon, but there is some fascinating science behind the doomsday hype.

Many times over our planet’s history, Earth’s magnetic poles have reversed, meaning that sometimes a compass pointing north will be aimed at Antarctica rather than the Arctic. This might sound strange, but it’s a relatively predictable quirk. Powered by the machinations of the planet’s spinning iron core, this process of geomagnetic reversal has been doing its thing without much fanfare for eons.

That is, until this week, when a book excerpt describing the phenomenon appeared online. Shortly afterward, numerous websites began trumpeting the doomsday around the corner, a geomagnetic apocalypse in which tumors run rampant, satellites fall from the sky, and life on Earth will cease to exist as we know it.

True, life on Earth almost certainly will be different than it is today in multiple thousands of years. But will these polar acrobatics have much to do with that?

First thing’s first: Are we all going to die?

Yes.

Wait, what!

We are all going to die, eventually. But chances are that we will not immediately—or even proximally—perish when Earth’s next geomagnetic reversal occurs.

Fine. So what is a geomagnetic reversal?

If geologic history repeats itself, Earth’s magnetic poles should eventually swap places. This much is undeniable. Based on the magnetic fingerprints locked into ancient rocks, we know that over the last 20 million years, magnetic north and south have flipped roughly every 200,000 to 300,000 years (this rate has not been constant over the planet’s lifetime, though). The last of these major reversals occurred about 780,000 years ago, although the Poles do wander around in between these larger flips. (What’s more, climate change seems to be shifting Earth’s geographic poles.)

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That means we’re a bit overdue for a total reversal, and some data do, in fact, suggest that a geomagnetic reversal is geologically imminent. But this does not mean a polar flip-flop is going to happen tomorrow, or even any time soon, and we’d put good money on North still being in the Arctic for a while—although neither we nor anyone else knows when the next total reversal will actually happen.

OK. But if it happens soon, won’t that be bad?

Also unclear. Scientists estimate that past polar flips have been rather sluggish, with north and south migrating to opposite positions over thousands of years. This is both good and bad if you’re concerned about how a geomagnetic reversal will affect life on Earth.

The sluggish polar meander is good, because it means we have time to prepare and can do our best to ameliorate any unpleasant effects before they get really unpleasant. But it’s bad, because our planet’s magnetic field helps shield us from damaging solar and cosmic radiation, and a protracted flip means Earth might be slightly less protected from harmful space rays for longer than we would like.

It’s also not very dramatic, because it means you won’t suddenly wake up and find out that your smartphone thinks Santa’s workshop is in the Southern Hemisphere.

Bummer, that sounds boring. So what will we actually notice?

The only major, noticeable effect that’s guaranteed to occur when the polar flop is finished is that your compass needle will tell you that North is in Antarctica and South is somewhere near Canada. This will make the names of the American continents temporarily confusing (at least, on a geologic time scale) but it’ll make for a good story in classrooms.

Another interesting consequence will be that animals that use Earth’s magnetic field for navigation—including birds, salmon, and sea turtles—could get lost during their routine journeys. Eventually they will sort this out, and all other things being equal, life will go on. Lots of doomsday prophets have tried to equate geomagnetic flips with mass extinctions, but the data just aren’t there.

So there’s nothing at all to worry about?

Not exactly. It’s true that when the poles do reverse, Earth’s magnetic field could get weaker—but its strength is already quite variable, so that’s not necessarily unusual, and there’s no indication it will vanish entirely, according to NASA. Why? Because it never has.

However, if the magnetic field gets substantially weaker and stays that way for an appreciable amount of time Earth will be less protected from the oodles of high-energy particles that are constantly flying around in space. This means that everything on the planet will be exposed to higher levels of radiation, which over time could produce an increase in diseases like cancer, as well as harm delicate spacecraft and power grids on Earth.

These are consequences we can prepare for, and as far as everything below the stratosphere goes, we’ll have a nice, thick atmosphere that can also help act as a shield.

For now, we’re doing a decent job of introducing carcinogenic toxins to the environment and otherwise altering the ways in which ecosystems normally function, so there are bigger things to worry about in the short term.

That being said, one total bonus of having a weaker magnetic field is that auroras will be visible from much lower latitudes, so the nighttime skies will be even more epic.