In very very small words please explain the idea of the magnetic poles switching places every so often. Does
the actually flop over screwing up insurance rates everywhere? Or is it just the magnetic field that moves? Is it an exact swap of North or South or does North end up in Fargo and the South Pole who knows where? How does it feel to any living creature? Does it require massive doses of dramamine or should you just tuck your head between your legs and start kissing your fanny goodbye?
Mama Maroon
“It is better to ask some of the questions than to know all the answers.”
I know some of you folk out there with university degrees in this kind of stuff will beat me to this, but – what the hey …
Just happened to have a copy of Discover magazine handy, October 2000, p. 53:
I explained once some time ago in a newspaper that the best analogy I have for why there are magnetic field flips is to imagine the molten section of the earth between the core and the crust as water swishing around in a bucket. Only we’re talking waaay long time periods, here. One swish is almost 3/4 of a million years. At one point, swishing the bucket, the water briefly “stops”. Then it swishes back again. When the Earth does this, it reverses the polarity of the magnetic field.
anybody know, is this the outer slushy core moving and sloshing around, or the inner solid core sluicing around the outer slush, that causes the magnetic fields to appear? a question I’ve always wondered,
jb
On a somewhat related topic, I have read things like “500 million years ago, the North pole was located in Africa”*****. I was wondering what this meant; was it:
Due to continental drift, the piece of land that now is part of Africa was once located at the North pole.
The entire Earth’s crust has shifted around the planet’s center, so that what is now at a low latitude was once at a higher latitude.
Relative to the stars, the Earth’s spin axis has shifted so that the Earth as a whole once had a different orientation.
(***** Cannot cite exact quote, so date and location are arbitrary.)
Do not confuse the Earth’s magnetic poles with its geograhic poles. The North Magnetic Pole is not located at 90 degrees North Latitude. It is located in far northen Canada (I forget exactly where). The magnetic pole precesses constantly, meaning it wobbles. It is my understanding that the Earth does not (nearly) revolve about the magnetic poles because they are magnetic, but rather that the magnetic poles exist due to coriolis effects on magnetic materials in the mantle and core and therefore line up near the geographic poles. It is easy to conceive that hundreds of millions of years ago, when the Earth was far more geologically active than it is now, that the mag/geo poles were not so neatly lined up as they are today.
Look ‘down’ on the earth at the north pole and you’ll see it spinning counterclockwise.
Look ‘down’ on the earth at the south pole and you’ll see it spinning clockwise.
It all depends on where you are.
At a guess (and this is a huge WAG) I’d say the molten core is spinning mostly eastward…maybe a bit north of due east. I.e. If you suddenly stopped the earth’s rotation (ignoring the devastation that would cause) the molten core would continue swishing to the east.
During this century of inbetween time during a flip; if there is no magnetic poles, does that mean that cosmic radiation is going to bombard the earth unimpeaded?
Look ‘down’ on the earth at the north pole and you’ll see it spinning counterclockwise.
Look ‘down’ on the earth at the south pole and you’ll see it spinning clockwise.
It all depends on where you are.
So, Jeff, explain to me once again why when I look in my swishing toilet bowl from the North Pole it swirls in the same direction as it does when viewed from the South Pole (or Australia.)
Cecil be damned! The physical world makes no sense to me and I have to keep asking and experimenting until I get it.
I really have enjoyed mulling over all the responses this thread has spit up. I have to admit a lot of the world whooshes over my head no matter how many times it is explained to me but I enjoy the sounds it makes as it whooshes past me.
And yes I can say “Cecil be damned” because I am and shall
always hope to remain…
anonymouse
The answer to your question is the Coriolis Effect.
However…Cecil is mostly correct on this one. Water does not drain in a preffered fashion in the northern or southern hemisphere. Basically the coriolis force on water in your bathtub is extremely small compared to other things that affect water draining (such as the shape of the drain, disturbances in the water, etc.). Under VERY controlled (laboratory) conditions the water in a sink would drain in different directions in different hemispheres but you’re not likely to achieve that degree of control at home.
Where you do see this effect is on extremely large things such as ocean currents or hurricanes. In this case the phenomenon are large enough for the coriolis force to add up to a significant portion of the forces affecting the system. (HIJACK: Can a hurricane ever cross the equator? Would it cease its spinning and break apart or is its total momentum far too high to be significantly altered at that point?)
The quick and dirty explanation to the coriolis force is due to the rotation of the earth. Standing in the northern hemisphere and facing the equator the earth is spinning to your left (Notice overhead photos of hurricanes in the northern hemisphere have them spinning counterclockwise or to your left as well). Standing in the southern hemisphere and facing the equator the earth is spinning to your right. It is this ‘opposite’ direction that makes weather and ocean currents rotate in opposite directions in the north or south.
As an aside airplane pilots and people shooting missiles long distances must take the coriolis effect into account if they expect to end up where they want to at the end of their flight.
Ken Kesey’s novel Sailor Song is set in the near future in Alaska and includes a magnetic pole shift as seen from the ground. Suddenly people see what looks like a gigantic purple strip of bacon, crinkly around the edges and making a sizzling sound, fly across the sky from north to south. All electrical devices on earth are permanently disabled. The newspaper has to be produced with a manual typewriter and carbon paper, the masthead printed with a potato.