Earth's polarity shift

I have heard that the Earth switches magnetic polarity at intervals lasting millions of years. Some have claimed that the event would be catastrophic to life if it were to happen today. Infact, if the intervals are somewhat consistent in occurence, it could be tommorow that the polarity will reverse. Proof of polarity shifts are in the ocean plates which are constantly being renewed by new mantle. The minute peices of iron ore supposedly point towards the poles before they solidify in the rocky solution. And they show that the poles have been reversing quite frequently during the past few millenia.

So what does everyone think the cause of this phenomena is? Will it really have a devastating effect on life? I know some animals use the polarity for navigation, will these animals quickly become extinct by migrating in the wrong direction? Will their loss cause significant damage to the food chain?

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It will mess up navigation and it might cause planes in the air to get lost and/or crash. Obviously it will take quite a bit of adjustment for birds to figure out that they need to start doing the opposite.

Really it isn't likely to be as bad as it sounds.

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• Cogito cogito ergo cogito sum. (I think I think, therefore I think I am.)

I'm so profound it hurts.

Originally Posted by Michali

I have heard that the Earth switches magnetic polarity at intervals lasting millions of years. Some have claimed that the event would be catastrophic to life if it were to happen today.

There are no major extinction events associated with polarity shifts to my knowledge. There is no biochemical reason that it should be fatal.

And they show that the poles have been reversing quite frequently during the past few millenia.

Not during millenia, but during intervals of about 10 - 20 million years.

So what does everyone think the cause of this phenomena is?

Rotating magnets routinely shift poles. The field degenerates and then reverses polarity. Look up magnetism on the web for a more detailed answer.

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"If sound science appears to contradict the Bible, we may be sure that it is our interpretation of the Bible that is at fault." Christian Observer, 1832, pg. 437

"Christians should look on evolution simply as the method by which God works." Rev. James McCosh, theologian and President of Princeton, 1890

I meant to say millions of years not millenia. Sorry about that.

What do you mean by a rotating magnet? Spinning like the earth is (with the poles fixed) or actually spinning head over end?

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Originally Posted by Michali

I meant to say millions of years not millenia. Sorry about that.

What do you mean by a rotating magnet? Spinning like the earth is (with the poles fixed) or actually spinning head over end?

I misspoke. I meant a flowing liquid where the flow rates are different at different parts of the liquid. http://www.phy6.org/earthmag/NSTA1C.htm

Note that the sun reverses polarity every sunspot cycle of 11 years.

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"If sound science appears to contradict the Bible, we may be sure that it is our interpretation of the Bible that is at fault." Christian Observer, 1832, pg. 437

"Christians should look on evolution simply as the method by which God works." Rev. James McCosh, theologian and President of Princeton, 1890

Although the polarity shift is often linked with total chaos, oceans covering lands, earth spliting apart, etc, By conspiracy theoriests and end time believers.

In reality, as most have said, there is no evidence to link disaster with a polarity shift.

We dont completly know how birds navigate. So we cant be sure how it would effect them, for all we know, birds dont care which way is north, just which way the field is aligned (up an down).

If I remember from school, it hasn't happend for quite some time, based on average time, its expected to be soon. But "soon" and "Soon" are different things as Soon may mean there are still a million years left.

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Wei wu wei

Green faeries

Oh I never thought it would be catastrophic. I just read that it was listed in the "top ten ways the world might end". It was from a major publisher too. I just can't remember who. It wasn't Christian or anything.

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JM: Magnetic reversals are aperiodic. In fact, there seems to be no way to predict when a reversal might happen. The last one occurred around 780,000 years ago. Initially, it was thought that the loss of the dipole field (the earth's field contains significant percentages of non-dipolar fields) would decrease the shielding from harmful solar radiation and result in extinctions. However, no correlation has been found between extinction and magnetic reversals and the suggestion is that the non-dipolar terms increase as the dipole moment decreases and result in the maintanence of the 'magnetic shielding'.
The most likely cause of the reversal phenomena is probably due to chaotic disturbances in the fluid motion of the outer core. For example, thermal blanketing of the core mantle boundary will affect the heat transfer across the core-mantle boundary and will cause the convective regime in the outer core to adjust. This adjustment may lead to a reversal. However, I should note that figuring out the dynamo nature of the earth's field and figuring out the mechanism(s) required for a reversal is an outstanding problem in Earth science and magnetohydrodynamics. It could lead to the award of a Nobel Prize in physics to someone so inclined to solve the problem.
Some cool experiments have been conducted in biomagnetism. Magnetotactic bacteria (they orient themselves for feeding) have been subjected to alternating magnetic fields. Bottom feeders will begin to swim upward during shortly after the 'reversal' but re-orient themselves rather quickly. SInce butterflies, such as the monarch also navigate by magnetism and have lived through reversals it is thought that they 'figure it out'. Cool stuff to be sure.

Cheers

Joe Meert