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Magnetic Poles May Be About To Flip
AGD writes "According to the Guardian, Earth's magnetic field - the force that protects us from deadly radiation bursts from outer space - is weakening dramatically. . The article goes on to say 'Earth's magnetic field has disappeared many times before -- as a prelude to our magnetic poles flipping over, when north becomes south and vice versa.'"
First off: we are not all gonna die. It has been 800,000 years since the last time the poles flipped. At that time, our ancestors were walking around, munching on wooly mammoths an giant sloths, etc., armed with such amazing modern tech as sharpened flint and fire. If they can take it, so can we.
Second, we have very little knowledge about how the poles are going to switch. There seems to be two options:
1. The poles are going to disappear, then reappear on opposite sides of the planet.
2. The poles will migrate over the face of the earth until they have effectively flipped over.
However, as geophysics usually shows us, there is a third, and much more complicated option, that is more likely. Simply put, the poles will weaken, and then split up into smaller magnetic zones, which will then wander all over the surface in an extremely complicated manner, and then coalesce on the oppposite sides. If you think this is a crackpot idea, you should check out past issues of Nature.
I'll also point out that no one really knows how the planet's magnetic field is generated. It is DEFINATELY not analogous to a regular bar magnet, because the core of the earth is much too hot to sustain magnetization of iron.
On global warming - much of the evidence is related to the melting of the polar icecaps. If the magnetic fields at the poles have been decreasing over the last 20 years, how much of the melt is due to more energetic radiation sliding down the field (weaker field, bigger V at the pole and greater cross-section of absorption for the energetic particles to penetrate). From memory, I believe that sat surveys of metropolitan areas have shown a decrease of 0.5 degrees in the same period (ground data is polluted by greater ambient temperature from concrete structures, bitumen etc) and its really the pole data that underpins much of the theory. Its not going to be fun when the poles do drift - we could end up with multiple pole pairs with high latitude magnetic effects in current mid-latitude areas. The auroras will be pretty but the disruption to HF radio is going to mean a much greater need for landline communications.
For a lark, I did the calculations for artificially imposing a magnetic field if the Earth ever lost its own.
:).
It turns out to be feasible even today, though horribly, horribly expensive. You'd build a mesh of copper cables around the equator (or superconducting, but copper's losses aren't that bad for this). Then you'd slowly ramp up the current until you have a magnetic field comparable in strength to today's.
Ramping up would be slow because of inductive power storage. The current loop and associated magnetic field store a *vast* amount of energy, all of which needs to be provided in order to bring the field up to strength. The present power output of all electrical plants on the planet over a decade or so would do it, if I remember correctly, so this is feasible. The power cost to maintain the field, even with copper cables, is much lower; put, say, a 10% tax on electricity, and you've paid for the extra plants to feed the mesh.
You'd use a mesh instead of a single cable _because_ of the amount of stored energy. If you break the current path of an inductor, current flows anyways, arcing across the gap. This only dies down as resistive losses across the gap dissipate the power stored in the inductor. Think about this - all of the inductor's stored power is dissipated in one place (the break), and we're storing an awfully large amount of power in this current loop. If the loop was a single cable and this cable was broken, you'd get something in the range of a 10-gigaton yield at the point of breakage. A mesh provides many alternate current paths, so breaks from sabotage or just plain wear can be repaired safely (as long as you overspec the current rating enough to allow the other paths to safely take up the load).
A copper cable a hundred metres wide, or ten thousand one-metre cables, would do the trick. You might _have_ to use copper, too; even if you spread the cables out to make a more uniform field near the Earth's surface, field strength near each wire would be much greater than the breakdown point of most superconductors.
We'd probably never bother doing this, but it's a fun thought experiment
This kinda freaks me out though..
Berto
If this has happened every 250,000 years, it's obviously not a threat to the existence of life on this planet.
Apparently this article is a flare, to get the public thinking about magnetic field reversal, to hype the upcoming disaster-movie The Core. Expect this story to appear on CNN soon.
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
this seriously stinks of hollywood making up news as a blockbuster is about to be released. they did it before with all those asteroid movies and then again with all those mars movies a few years ago.
from the article:
Paramount's latest sci-fi thriller, The Core - directed by Englishman Jon Amiel, and starring Hilary Swank and Aaron Eckhart - depicts a world beset by just such a polar reversal, with radiation sweeping the planet.
wtf??
i could live a little longer in this prison
I have to wonder what definition of "feasible" you're using that includes a project requiring "the present power output of all electrical plants on the planet over a decade" and more copper cable than has ever existed.
Something that we could conceivably do within 50 years if we decided we really wanted to (along the lines of the Manhattan Project).
As opposed to, say, building a Dyson Sphere or some other project that requires either vastly more resources than are available, or materials that we have no idea to produce.
Time now for some math.
Suppose a swallow is born 500 years from now. It's life span is what, 2-3 years? At the beginning of its life, the earth's magnetic strength is 0.5 as strong as it is today (500 years left/1000). By the end of the swallow's life it is 0.497 as strong (497 years left/1000), for a 0.6% change in magnetic field strength during the course of it's entire life. Less than one percent! Yeah, I think a swallow can deal with that.
If you are born with something (sound, energy, happiness, whatever) that is weaker than it was 1000 years ago, you do not even notice. It's that way all your life, and you cope with it. You never even consider it.