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Why is polarity shift such a big deal?





boinsterman
There have been a number of apparent predictions that the magnetic poles will reverse their polarity soon. This apparently happens every 18,000 years (?) or so. Their orientation changes gradually over time as it is. (The north magnetic pole is in northwestern Canada and moves a few miles each year as the planetary core rotates in place.)

I recently saw a commercial (for a consumer product) which suggested that some people believe the polarity shift would cause the planet to lose all or most of its gravity for a short time, causing anything not nailed down (people, etc.) to float in orbit around the Earth.

First, the physicists define the magnetic force the magnetic force as a different force than gravity. I know of no scientific basis for believing that gravity would be affected.

Second, since such a massive loss of gravity would result in losing much of our atmosphere, and in most land animals, plants, and soil, plus a lot of water, to leave the atmosphere and then crash back to the surface, these events should be recorded in the geologic and paleontologic records. (How any life could survive at all, as depicted in that scenario, is questionable.

I realize that the commercial was likely exaggerating, to say the least. It treated the subject lightly, almost humorously, as way to psycologically associate not having their product with catastrophe. But even a low-level, worldwide earthquake would leave some evidence, would it not? Mass amounts of skeletons would appear periodically in sediment layers all over the world. Also, it is likely that tribal lore all over the world would have some reference to the most recent polarity shift.
Bikerman
It is obviously either a hoax or an idiot....of course gravity would not be affected. G=m1m2/r^2 No mention of electromagnetic fields of any type there Smile
kelseymh
As Bikerman said, either stupidity or hoax to steal your (or someone else's Smile ) money.

Magnetic reversals happen irregularly, not on any fixed cycle. That fact, all by itself, is what allows geologists to use them for very precise dating of rocks up to 200 million years old or so (see the big image at the bottom of this post).

[img]http://upload.wikimedia.org/wikipedia/en/c/c0/Geomagnetic_polarity_0-169_Ma.svg[/img]

There are side-effects from geomagnetic reversals which will affect technology, "civilization," and possibly the wider ecology.

Evidence from volcanic ash fields suggests that at least some reversals can happen extremely quickly, in a few decades. Prior to the advent of GPS, such a rapid change in magnetic direction would have played havoc with navigation -- shipping and air traffic would be badly disrupted if their navigational charts and software became completely obsolete. Today, that could still be a major problem, but we have technology in place which can substitute for magnetic navigation in the interim.

Since the geomagnetic field is generated dynamically (through a dynamo process in the Earth's liquid outer core), any reversal must be accompanied by some period of zero field, when the dynamo has stopped, but hasn't yet restarted in the opposite direction. The geomagnetic field is what protects the surface from radiation bombardment by the solar wind and cosmic rays. Without it, the level of "background" radiation would increase significantly.

Charged particle radiation can damage or destroy the electronics systems of satellites, electrical distribution grids and communications systems. Existing systems, other than geosynchronous and deep-space craft, are not designed with the shielding necessary to withstand the full brunt of such radiation. Higher radiation at Earth's surface could lead to higher rates of cancer, damage to domesticated crops or livestock, or other environmental damage.[/img]
boinsterman
That's the kind of detailed info I was looking for. Thanks, Kelseymh.

kelseymh wrote:

Charged particle radiation can damage or destroy the electronics systems of satellites, electrical distribution grids and communications systems. Existing systems, other than geosynchronous and deep-space craft, are not designed with the shielding necessary to withstand the full brunt of such radiation.


Do you happen to know the name of the type of shielding such craft would use? Can it be applied to buildings cost-effectively? (There would be no need to design for a vacuum, so I would think it would be at least somewhat less costly than for spacecraft.)

And, if the danger to living people, livestock, etc. is significant, can anything else be done to reduce the risk? Underground or underwater shelters come to mind, but I doubt there would be enough space for all, although your description suggests we would have plenty of warning.

Edit: This could be a good basis for a science fiction story, given it's plausibility.
Dennise
Because, after the shift everyone would need to hold their maps upside down or people would get lost! (wink, wink)
Bikerman
No, you have forgotten to include the fact that Australians will then be standing uright, rather than upside down. This means that the need for map-reversal will be cancelled.....
Dennise
Bikerman wrote:
No, you have forgotten to include the fact that Australians will then be standing uright, rather than upside down. This means that the need for map-reversal will be cancelled.....


But the OP is referring to Earth's magnet shift not flipping the entire planet pole to pole!

It would be cool however were we northern hemispherians to experience the Ausies upside-down world and feel the fear of falling off the planet. Would we need to reverse the calendar month order to keep people from getting too confused?
SonLight
The updise-down maps (which were obviously a joke in the first place) would be needed only if a magnetic compass were used for navigation. If the GPS system survived the event, presumably we could still pretend that we are standing right-side-up (which none of us really are, of course). Wink Laughing
Bikerman
NoNo....the Australians are absolute down, as determined by the flux lines of the EMF (Earth's Magnetic Field). Applying Flemings left hand rule tells you which way the forces are acting in such cases, and it tells us that the Australians are down and the western hemisphere is definitely up.
Of course, this means that the Australians are held in place electromagnetically, not gravitically, because gravity could never hold them onto the earth when they are suspended upside down - that's daft. Gravity is really weak. It's OK when all your weight is pushing down into the earth - it'll hold you then. But if you are upside down then your weight is all pulling you upwards and gravity can't match that. I bet you've forgotten to reverse the sign on the f=ma calculation, or perhaps forgotten to add the vector for weight?
ocalhoun
I'll admit: I burst out laughing when I read the part about temporarily losing gravity. ^.^

...And as for the most recent turn of conversation, I'll just quote Pinkie Pie:
"Silly, the Earth is round, there is no up or down!"
Bikerman
Oh really. So this football in my hand doesn't have an up or down?
Funny.....I put my little soldier figure on the top and he is quite happy. Can't get him to stand on the bottom without tape though.....

I guarantee to give your physics a work-out here. Anyone who doesn't really understand is normally found out in about 2 or 3 postings from now Smile
ocalhoun
Bikerman wrote:
Oh really. So this football in my hand doesn't have an up or down?

That's the joke ^.^
Anyway, laws of physics don't apply to Pinkie Pie.
BigGeek
Bikerman wrote:
Oh really. So this football in my hand doesn't have an up or down?
Funny.....I put my little soldier figure on the top and he is quite happy. Can't get him to stand on the bottom without tape though.....

I guarantee to give your physics a work-out here. Anyone who doesn't really understand is normally found out in about 2 or 3 postings from now Smile


I'm so confused, I just can't tell what's up or down anymore Laughing

I think I need to retake all the physics classes again.....I forgot....which way is up? Shocked

Help, I'm floating off into space..... Rolling Eyes
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