So, if the earth’s magnetic fields did switch back… how would that affect our compasses, refrigerator magnets, etc? who cares about radiation… is this going to make everything on my fridge fall off?
see http://www.cnn.com/2003/TECH/science/12/12/magnetic.poles.ap/index.html
I asked this question about 3 years ago and never got any answers. I hope that somebody can add something. I want to know if there is a chance that we end up in East America instead of North America or something like that. And what happens to compasses?
Aside from the environmental effects, the only thing that will happen as far as magnets go is that compasses will reverse. But don’t worry about any “official” directions changing. Using the magnetic poles is a crude means of determining direction anyway, and nowadays it’s done with things like GPS which don’t rely on the Earth’s magnetic field for direction information. All you’ll have to do is swap the N and S stickers on your compass.
Compasses would have problems, but I don’t see why you would think your refrigerator magnets would have any problems. Magnetism itself does not reverse, just the Earth’s field.
Compass needles point along the direction of the magnetic field they are in. Magnetic field lines arch out from the north pole of a magnetic and loop around to enter the south pole, which means compasses point toward the south pole of magnets. Our earth, modeled as a bar magnet embedded along its axis of rotation (actually I think it’s slightly off, but for purposes of this discussion, we’ll pretend it’s the same), would have the south magnetic pole directly below the north geographic, and the north magnetic pole directly below the south geographic pole. This way, compasses point to to the north (along the field lines as they go into the south magnetic pole). If the earth were to switch magnetic orientation, assuming it is an immediate process, our compasses would then point to the south. Your refrigerator magnets would be unaffected, because they work by interacting directly with your refrigerator; the earth’s magnetic field is irrelevant. When a refrigerator magnet interacts with a fridge, the attraction force is much much stronger than any force derived from the earth’s magnetic field, which, compared to a bar magnet under such conditions, is very weak in comparison. So basically compasses would point in the other direction.
This is assuming a 180[sup]o[/sup] reversal in the field. What if the movement is only 90[sup]o[/sup]?
In that case, your compass would have to be relabelled every time you travelled more than a few hundred miles - magnetic north would not be in the same direction on different parts of the globe. However, that’s not as likely to happen. It’s thought that the magnetic axis of the Earth is linked to the planet’s spin axis.
The magnetic field has reversed lots of times, and as far as I’m aware it’s been a 180 reversal in each case. As long as the earth spins around its current axis, I don’t see how it could be otherwise.
Aside from the mechanism that produces the Earth’s magnetic field (which is open to some debate), there is another good reason why the poles would not be stable if they were not fairly close to the axis.
If, as Adam Yax suggested, the axis were to swing 90° (putting the north magnetic pole at some fixed point near the equator), the entire planetary field would be completely rotating ever day (vs wobbling, as it does now).
This would represent an enormous energy drain due to many causes, such as the interaction of the rotating planetary field with the fairly fixed solar field effectively creating a generator. While this could potentially produce any number of intriguing effects,the point I want to make is that it is energetically unfavorable - more so at 90° than 89°, more at 89° than 88°, etc. The net effect would be a steady energetic “pull” towards the pole.
This energetically unfavorable effect is much stronger at deviations near 90° than at deviations near 0°, so the “pull” attracting the current magnetic pole (11° from the rotational pole) is very modest compared to what it would be at 45° or 90°. Still, even energy of the current situation is far from negligible, and in some theories, it is a major factor contributing to the reversals of the poles.
PBS/Nova and Channel 4 recently did a documentary about this: Magnetic Storm (transcript and images here). Apparently the field won’t just neatly flip, but will break up into a rapidly-varying chaotic pattern that’ll eventually reform with N/S reversed. During the changeover, they say there will be problems: increased incidence of cancer due to cosmic rays getting in; a lot of aurora activity (not just at the geographic poles); and magnetic compasses wouldn’t be much use for the duration. However, as Exapno Mapcase said, it has happened many times before over geological history, so the chances are we’d survive it.
You don’t change your compass, you change your maps. Aviation charts for example show the magnetic variation with lines akin to a coutour map. You apply that as deviation to your compass (IIRC, if not may Johnny L.A. correct me on variation/deviation) to get true north.
We don’t know.
I am not aware of any mass extinctions or not so mass extinctions associated with reversals.
The dating of magnetic reversals for the past 65 or so million years can be fairly accurate. Magnetic reversals were first discovered in mapping the ocean floor. Knowing the spreading rate and the distance can give a fairly good age for the reversal. The dates can be confirmed with radiometric dating. But the dating techniques cannot pin down the reversal time with any accuracy - except to say that it is rapid. And that is rapid in geologic terms. The duration of the reversal period could be hours to several thousand years.
The lack of new speciation or die offs associated with reversals most likely means that whatever of God’s little critters where skittering about during past reversal probably didn’t know anyting was different. And if they did they found a way to get over it.
We don’t know.
I am not aware of any mass extinctions or not so mass extinctions associated with reversals.
The dating of magnetic reversals for the past 65 or so million years can be fairly accurate. Magnetic reversals were first discovered in mapping the ocean floor. Knowing the spreading rate and the distance can give a fairly good age for the reversal. The dates can be confirmed with radiometric dating. But the dating techniques cannot pin down the reversal time with any accuracy - except to say that it is rapid. And that is rapid in geologic terms. The duration of the reversal period could be hours to several thousand years.
The lack of new speciation or die offs associated with reversals most likely means that whatever of God’s little critters where skittering about during past reversal probably didn’t know anyting was different. And if they did they found a way to get over it.
Here is a good explanation of the arrangement of the Earth’s magnetic field and some maps showing the pole and the shape of the field
padeye, you were close. The term for the difference between geopgraphic vs magnetic direction is “variation.” “Deviation” is the difference between magnetic and compass direction, i.e. it’s the correction factor applied to offset calibration errors in your particular compass device.
I recenlty read, but can’t now generate a cite (or site!), that if the Earth’s mag field did switch, there’d be a period of a few dozen to a few hundred years where it’d be a chaotic mess before settling down to more-or-less opposite of what it is today. That’s an instant switchover on a geological timescale, but for we humans that’s be a long confused slog during which magnetic compasses would be almost, if not completely, useless.
Between GPS and gyrocompasses we could get by nowadays, but had that happened a few hundred years ago, say 1200-1500 CE, the exploration of the Earth would have been a LOT harder and may not have even been doable.
See the “Magnetic Storm” transcript I cited above. It’s an interesting thought how differently human history might have played out if it had coincided with a reversal.