Geomagnetic Reversal

I received a text message from a family member yesterday asking “Did you ever hear of the polar shift?” Intrigued, I replied that I did, and guessing where this was going, added that, no, we were not in for a doomsday event in the near future. Today, I was able to follow up with a more detailed email response to ease her and her co-workers’ fears. What follows is most of that email!

By pole shift, that usually means that the rotation of a planet has changed drastically, causing all kinds of havoc on geology and weather. The Earth’s rotation is very stable and may only wander by less than a degree over a million years, so that’s not worry. It would take large impact, like ones that the planets suffered 5 billion years ago, to really knock a planet around.

I’m going to assume that we’re talking specifically about something called geomagnetic pole reversal, meaning that the poles of the Earth’s magnetic field will actually reverse polarity. So, to start we need to know that the Earth has a magnetic field, often pictured to look like a bar magnet, that is created by rotating, liquid metal in the earth’s core. It is why our compasses point north and it protects Earth from lots of harmful particles, called cosmic rays, that come from the Sun and elsewhere.

Despite the simplistic picture above, the magnetic field strength can increase and decrease, and the poles can actually completely flip! In fact, the magnetic field of our sun flips every 11 years or so, which is tied to the solar cycle of increasing and decreasing solar activity. Since the sun is a ball of gas that doesn’t rotate uniformly, it makes sense that the magnetic field will get twisted and do funny things. The Earth’s is much more stable, but not completely so. It has been shown by the direction in which magnetic materials in ancient rocks point that the Earth’s magnetic field has flipped many time in the past!

This isn’t a sudden change, however, and takes thousands of years, over which time the magnetic field strength may decrease. Current work shows that the magnetic field is decreasing and that we may be due for a polarity reversal… but only over the next couple of thousand years.

What will happen to us when this occurs? Well, probably nothing. In fact, our human-like ancestors homo erectus lived through the last polarity reversal with no signs that the population suffered any damage. In fact, there has never been a strong link to polarity reversal and any large extinction event. What is most vulnerable is our technology. During a period when the magnetic field is weak (or solar activity unusually strong), solar storms can knock out satellites, disrupt radio communications, or even cause large power outages. However, since these changes will be gradual, I suspect that our technology will evolve to cope with the changing environment. Even now, scientists are working on early-warning systems for solar flares, such that important satellites and even astronauts can hunker down and prepare for the blast of high energy particles. Of course, I’m going to pimp one such effort that is going on in my own lab with the Solar Radio Burst Monitor.

Why are we hearing all about this now? Well it’s the 2012 doomsday nonsense that is quickly selling books and now a movie. This is tied to something called the Mayan long count calendar, which is supposedly due to expire in 2012, signalling the end of the world. People have come up with all kinds of pseudo-scientific scenarios on how the world will end, and they are not entirely based on fact and in fact quite easy to dissect. If you are interested, I could get into it more, or you can read a fascinating series of articles by Ian O’Neill on this at Universe Today.

But really, if the Earth was due for some catastrophic calamity in three years, astronomers would be screaming at the top of their lungs to do something about it! And if there was nothing we could do about it, well we’d all quit our jobs and live out the rest of humanity’s span on some tropical island sipping strawberry margaritas. Or maybe that’s just me.