This site, descibes the mechanisms of the magnetic field and the theories for polarity reversal --“we don’t know”.
Suppose we wake up tomorrow and and it’s happened, north is south and south is north. What are the RW consequences?
I can think of a few, mostly to do with navigation. Recalibrating magnetic compasses. Recalculating navigation tables based on compass readings.
What else? Could it it have negative consequences on the small scale fields generated in transistors? Or somehow influence electric motors? Could our electrical systems fry because the energy “tries” to flow backward?
Does such a global event result in a few lost backpackers and small plane crashes, or something more catastrophic?
It’s not the new direction that is the problem, it’s what happens inbetween.
There is a period est. at 200-400 years when the Earth has little or no magnetic field. And since the magnetic field shields us from solar wind and cosmic rays, bad stuff will happen.
BTW, these reversals happen on a regular basis and we are due for one in the next 1000 years. Time to start stockpiling tinfoil hats. (And I bet you thought those folks were actually crazy.)
A more complete answer than mine is sure to come soon, but I will point out the following.
The Earth’s crust is forming in fissures at the bottom of the sea. The lava flows out and makes new earth.
Some of the material created likes to align itself with the magnetic field of the Earth.
If you know how quickly the lava forms new earth, and you check the existing structure (from the lava flow over x years) a determination can be made as to how long between polar magnetic reversal.
Some of the material will be pointed north, and at some (x) distance other material will be pointed south. Etcetera.
So far as I recall, that is how they know the durations.
It’s late.
I’m tired.
Science class was years ago.
Umm, I didn’t say they happened that often. I said that the next one might be soon. E.g., March 25th happening on a Monday occurs about once every seven years. But the next one is tomorrow (as I write). There is an obvious distinction. Sheesh.
Um, you didn’t say the next one “might be soon”, you said that “we are due for one in the next 1000 years.” I’d still like to know where you got that figure.
From this article, it seems the pole’s movement may be picking up speed. Making the big assumption that it will continue on its present course and speed, it will be in Siberia (as opposed to it’s current location in Northern Canada) in 50 years.
Here is a site by the scientist cited in the CNN article describing his research in more detail:
<trying get a bearing on the OP and re-orient this thread>
The question wasn’t when it would happen or how long it would take, it was 'how would it affect us?"
I don’t think it would have a measurable effect on motors or transistors. I’m not too sure about the electrical grid, but I expect that solar storms would mess them up a heck of a lot more than a change in magnetism.
The only thing I can think of is induced current in Low-earth orbit satellites. I think it’s just a small voltage differential that has to be filtered out of the satellite’s electrical systems.
Oh, some migratory animals use the magnetic field to find their way around. If Santa ever got home, he might find the north pole infested with swallows and monarch butterflies.
A) I’m not sure that it is true that the statement that I underlined above is correct. Do you have a cite?
My understanding is that the field is composed of a dipole field having a north and south pole, plus a lot of higher order modes. It is entirely possible that the energy in the dipole field is transferred to the other modes and the total field is about the same during the reversals, it just doesn’t have a definite orientation.
My source for this is an article by Dr. Stephen G. Brush, University of Maryland, in the book Scientists Confront Creationism. Dr. Brush has this to say, “‘the magnetic dipole held is being driven destructively to smaller values by fluid motions which transform its magnetic energy into that of the near neighboring modes rather than expend it more directly as Joule heat’(cite from 1967 ESSA report by McDonald and Gunst) . In other words, the energy is being transferred from the dipole field to the quadrupole field and to higher moments rather than being dissipated as heat. This implies that the value of the dipole field could not have been much greater in the past, since it is limited by the total magnetic energy, which does not change very rapidly.”
B) In addition, it is my understanding that there is no evidence of any detectable disruption of life during previous reversals.
But the effects depend on how fast the change occurs, and what the intermediate state looks like. If the magnetic field disappeared for a while (say, more than a few years) I’d worry about the effects of solar radiation. Most satellites in low earth orbit will be in trouble, because they depend on magnetic force for attitude control. (Actually they usually use momentum wheels but if the satellite picks up too much angular momentum, it has to be dumped using magnetic torquers.) They could be reprogrammed if the field polarity reverses, but if the field disappears they won’t work.
If the reversal happened really fast, like a matter of hours, the power grid will probably sustain severe damage. Solar eruptions just jiggle the magnetic fields a bit; if the disappeared or reversed quickly, the induced current would be far greater.
Magnetic sensors are still widely used for sensing the direction of vehicles and various machines. Those will be in trouble.
I can’t remember if any migratory animals sense and use the magnetic field - anybody know?
Cites about “great biological changes …” from other than from this source would be nice.
According to Britannica and other sources, the results from investigations into coincident biological effects, like increased mutation, have been inconclusive.
One more time, the above reference and others all agree that the evidence shows that the field that reverses is the dipole field. All other higher order fields seem to persist and even strengthen because of energy gained from the reduction in the dipole field. During the reversals the earth still has a magnetic shield against harmful particles from the solar wind. Weaker maybe and non- (or perhaps more accurately multi-) directional, but still there.
Quite obviously humans have gone through such a dipole field reversal. Also, quite obviously those humans didn’t know that the field was reversing and so didn’t take, or even have the means to take, special precautions to guard against an increase in ionizing radiation. They must have made it or we wouldn’t be here to fret about the possible effects.
Those extant lifeforms that have some sense that detects magnetic fields for one use or another obviously either survived, not as individuals maybe but as a species, or else have developed that capability since the last reversal.
And besides that, the probability that such a reversal will occur while I’m around to see it are vanishingly small. It will be your problim, if any, not mine. Ha Ha.
