My understanding is that occasionally the magnetic poles of the earth do a flip-flop. Here are my questions:
Which pole, currently, is the positive, and which the negative?
Considering that we haven’t had a polarity swap in recorded history (we haven’t, right?), is anyone worried about the next one?
How long does the swap take? Do we wake up the next morning with our compasses pointing the wrong way, or does it take a while?
Is it a big deal for our current level of technology (“OH MY GOD! WE HAVE TO RECALIBRATE NORTH AMERICA!”) or kind of a grumble-grumble go switch the doohickey sort of a thing?
Ken Kesey fictionally imagined a pole flip in his novel Sailor Song, set in Alaska. The people see what looks like a gigantic purple strip of bacon flying across the sky from north to south, making a sizzling noise. (That’s some of the electromagnetic energy being transferred, I suppose.)
All electrical circuits and gadgets cease working from then on. No phones, no lights, no motorcars, etc. The local newspaper has to be produced on a manual typewriter with carbon paper. Its masthead is printed with a carved potato.
I don’t know if this scenario has anything to do with the actual science … or if any scientist really knows what to expect. Awaiting the scientific Straight Dope on this question.
The magnetic poles are not negative and positive, that has to do with electron and current flow, they are north and south magnetic poles. The magnetic field of the earth is believed to be caused by flowing iron within the core. The poles can shift but gradually. You won’t find your compass pointing the wrong way some morning but
Magnetic fiends and conductors can create electrical currents (that’s how a generator works after all) but I don’t see how anything happening with the earth’s magnetic field would have any effect at all on phone systems, automobiles, or anything else you list. I can however picture a lot of lost boy scouts, wandering aimlessly through the woods tapping furiously on their magnetic compasses.
The magnetic field of the earth would have to flip pretty fast in order to generate an electro-magnetic pulse big enough to knock out electrical equipment.
The weakening and reversal of the magnetic field gets space in the media from time to time. However none of those stories point out that the field that is weakening and that reverses is the dipole (i.e. two poles, one north and one south) field. The total magnetic field consists of that plus other, higher order fields (more poles) which accounts for all the wiggles in the isogonic lines on a magnetic deviation chart. All of the sites that I turned up in a Yahoo! search talked only of the dipole field weakening and reversing.
According to Prof. Steven Brush (U. of Maryland) in the book Scientists Confront Creationism, the then current (1983) evidence was that as the dipole field weakens the other fields strengthen and the total magnetic energy of the field stays pretty constant.
This makes sense if the field results from motions of the core of the earth. Right now the circulation of the core would be quite orderly producing a strong dipole field with some turbulence here and there producing small, high order fields. However, if the core circulation is becoming more turbulent then the dipole field would weaken while the others strengthen. And quite possibly about the same amount of energy is put into the total magnetic field, it’s just apportioned differently among various field components.
It is doubtful that there would be any great effect except on birds and other animals that use the magnetic field for navigation, assuming any do that. The atmosphere is what protects the earth from the solar wind and other radiation from space and that isn’t likely to disappear. As scotth points out, there have been previous reversals and there don’t seem to be any large biologic upheavals that correlate with them.
Actually, without a strong dipole component we probably wouldn’t have such pretty aurorae. The field steers high speed solar wind particles to north and south where they ionize the atmosphere and give us those beautiful displays.
One site, a religious one touting the end times did mention that without the field the solar wind would strip away the atmosphere exposing the surface to greatly increased radiation. However, if the atmosphere were stripped away (and it hasn’t been in the past so why should it be now?), radiation sickness wouldn’t be all that much of a problem. And, of course, Venus and Mars both maintain an atmosphere without a magnetic field.
As Padeye said, magnets have north and south poles, rather than positive and negative, but this is probably a good time to introduce even more confusion: at the present time, the North Magnetic Pole of the Earth is a south magnetic pole and the South Magnetic Pole of the Earth is a north magnetic pole.
That’s why the north pole of a compass points to the north–because “opposites attract.”
I still haven’t (and have never seen) an answer to one of the OP’s questions:
HOW LONG does the switch take? Is it a matter of years? Centuries? Seconds? Do we start noticing that the north magnetic pole is now in Canada, now in North Dakota, now Mexico, etc., etc., until it winds up somewhere in Antarctica within a few days? Does it just go FLIP, all of our compass points spin like crazy for a few seconds, and then realign to point south? Does it gradually weaken so that the compasses don’t align with any particular point, and then gradually regain strength with a reversed orientation?
toadspittle, no one knows. Large scale flips have not been observed, and the evidence is ambiguous. On the other hand, small scale changes in the magnetic field are observed–but that doesn’t mean that they are part of a large change. They could be.
I knew there was something devilish about magnetism…
IIRC, the current thinking is that the reversal might take only a thousand years or so. The blink of a geological eye. There are also recent signs of a weakening of the field. Maybe it’s already starting…
The article Padeye linked to (and boy, was that guy tough to read) mentioned that the current weakening of the dipole field will bottom out in about 1200 years and could either go back to what it was, or the poles could switch. Either way, the dipole field would eventually regain its strength.