An intriguing possibility was reported on Science Daily this morning:
Earth’s last magnetic reversal took place 786,000 years ago and happened very quickly, in less than 100 years — roughly a human lifetime. The rapid flip, much faster than the thousands of years most geologists thought, comes as new measurements show the planet’s magnetic field is weakening 10 times faster than normal and could drop to zero in a few thousand years.
Why would this matter? The article continues:
And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates. The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.
When will this happen? That’s the big question behind the headline. Soon, warn geologists. But their “soon” in geological time doesn’t mean the same as “your breakfast will arrive soon” in a restaurant. It seems overdue for a flip, but no one is sure when that might happen. A 2002 story in The Guardian warned that it was imminent – in geological terms:
“Some experts have stuck their necks out to predict that we can expect the next reversal some time in the next 2,000 years.”
I think we can have that cup of tea while we wait. It may not happen in our lifetimes. But, the article has that shock effect nonetheless:
The Earth could be about to turn upside down. The planet’s magnetic field is showing signs of wanting to make a gigantic somersault, so that magnetic north heads towards Antarctica, and magnetic south goes north. Compasses will point the wrong way, and migrating birds, fish and turtles are going to be very confused.
Just when this will happen, how long it will take and what the consequences will be, is difficult to fathom. What is not in doubt, though, is that it will happen. About every half a million years or so, the Earth’s magnetic field flips upside down.
And that’s the worry: every half-a-million years is a lot less time than the 786,000 years since the last flip-over. This summer, Scientific American warned it could happen sooner rather than later:
Earth’s magnetic field, which protects the planet from huge blasts of deadly solar radiation, has been weakening over the past six months, according to data collected by a European Space Agency (ESA) satellite array called Swarm.
The biggest weak spots in the magnetic field — which extends 370,000 miles (600,000 kilometers) above the planet’s surface — have sprung up over the Western Hemisphere, while the field has strengthened over areas like the southern Indian Ocean, according to the magnetometers onboard the Swarm satellites — three separate satellites floating in tandem.
The scientists who conducted the study are still unsure why the magnetic field is weakening, but one likely reason is that Earth’s magnetic poles are getting ready to flip, said Rune Floberghagen, the ESA’s Swarm mission manager. In fact, the data suggest magnetic north is moving toward Siberia.
So we wait, unable to do anything about it. Have another cuppa, if you must. Yes, you have time.
Meanwhile, you can read up on the change in the sun’s magnetic field, something that happens every 11 years or so:
The sun’s magnetic field changes polarity approximately every 11 years. It happens at the peak of each solar cycle as the sun’s inner magnetic dynamo re-organizes itself. The coming reversal will mark the midpoint of Solar Cycle 24. Half of “solar max” will be behind us, with half yet to come.
Hoeksema is the director of Stanford’s Wilcox Solar Observatory, one of the few observatories in the world that monitors the sun’s polar magnetic fields. The poles are a herald of change. Just as Earth scientists watch our planet’s polar regions for signs of climate change, solar physicists do the same thing for the sun. Magnetograms at Wilcox have been tracking the sun’s polar magnetism since 1976, and they have recorded three grand reversals—with a fourth in the offing.
Solar physicist Phil Scherrer, also at Stanford, describes what happens: “The sun’s polar magnetic fields weaken, go to zero and then emerge again with the opposite polarity. This is a regular part of the solar cycle.”
A reversal of the sun’s magnetic field is, literally, a big event. The domain of the sun’s magnetic influence (also known as the “heliosphere”) extends billions of kilometers beyond Pluto. Changes to the field’s polarity ripple all the way out to the Voyager probes, on the doorstep of interstellar space.
