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AstroChuck's avatar

What is the cause of reversals in Earth's magnetic field?

Asked by AstroChuck (37278points) November 27th, 2009

Every so often (the range is between tens of thousands and several millions of years) the polarity of the Earth’s magnetic field switches. What causes this change? Why is there such an extreme variance in the years between these shifts? Has any pattern been determined in the timing between each event?

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17 Answers

ModernEpicurian's avatar

I have a geologist friend and his reply was “Fuck knows”.

I don’t have much of a chance of answering this myself.

He states one theory, this is that the motion outer core shifts every Xnumber of years, this could be dictated by a secondary cycle in the convection currents dictating the movements of materials in the core.

But as I said, theory. He says it’s just one of the (many) things we don’t yet know. I’ll tell him to find out for you. Life’s work and all that.

lloydbird's avatar


LocoLuke's avatar

For all we know, they could be the result of an extra-terrestrial on the other side of the moon tuning his intergalactic radio =D
The way I understand it, they’re completely random and most likely depend on a number of independent variables which nobody knows about. Some (stupid) people have used them as another predictor of the world ending. “It hasn’t happened for a long time, and it’s long overdue. The next time will rip the earth in half!” or something like that…

FireMadeFlesh's avatar

I suggest you do some reading on Dynamo Theory. It is a long time since I have, and I barely understood it at the time, so reading it yourself will be much better than any explanation I can give. It is all about currents in the liquid regions of the Earth’s core, which are predominantly iron. This is quite helpful, as is this one.

mattbrowne's avatar

Unsolved mystery, I’m afraid.

Christian95's avatar

I think it Earth’s core and Sun related

TheCreative's avatar

I heard it’s every 26,000 years (I could be wrong) and that the next one is coincidentally in 2012. Every earth cycle.

AstroChuck's avatar

@TheCreative- Sorry to tell you but your source is wrong.

jambon_777's avatar

Here’s just something I found on Google

In the year 2012 the earth reaches an extreme point in a cycle of approximately 26,000 years. The open magnetic field lines at the north pole of the earth will be pointing towards the sun, receiving a peak amount of solar particles. The sun’s 11-year cycle of activity will also influence earth’s weather more strongly during this time.”

TheCreative's avatar

@AstroChuck Aha and why is that? :p

AstroChuck's avatar

Because it’s been nearly 800,000 years since the last shift, not 26,000.

TheCreative's avatar

@AstroChuck Oops!

I was looking around and found this and thought it was pretty cool.

Precisely at midnight on Dec. 21, 2012, the planets Pluto, Uranus and Neptune will be in perfect alignment, an extremely rare event that takes place only once in 26,000 years.

The Mayan calendar has predicted this long before the telescope was invented. The Mayans were able to predict eclipses of the sun, although these were not visible to them. They were able to calculate the average revolution of Venus with an error of just one day in 6,000 years.

How these ancient and simple people were able to do all these without the use of modern instrument has never been discovered. Nor why their civilization suddenly vanished around 800 CE.

This cosmic event which will occur on Dec. 21, 2012 is known as “galactic synchronization.” This means that the earth and solar system will be in line with the plane of our galaxy, the Milky Way. According to the Mayan calendar, this astronomical synchronization marks the end of the present world age or cycle...Link

AstroChuck's avatar

Again, your source is full of shit. We just had a “grand alignment” of the planets in 1982 (with all kinds of predictions of massive earthquakes, floods, etc…). It came and went and nothing happened. We had another in 2000 (but not as perfectly aligned) but I don’t believe one is scheduled for a while. I think the Mayans were about as accurate as Nostradamus was.

FireMadeFlesh's avatar

@TheCreative Pluto, Uranus and Neptune are not visible without a telescope. The Mayans could not have known when they would intersect when they could not see them.

The 2012 business is all about the phases in the rotation of the galaxy. The Mayans arbitrarily chose the founding of their culture as the starting point, and divided the cycle into fifths. 2012 is one fifth of a revolution since the founding of their culture. They say one of their original leaders now lives in the centre of the galaxy.

I agree with @AstroChuck; the Mayans were full of shit. I think you’ll find that 2012 is just another year, with just another Olympics.

TheCreative's avatar

@AstroChuck Calm down buddy, didn’t do too much research. Just something I found on Google.

AstroChuck's avatar




There. I’ve calmed down now.

fireside's avatar

I’m pretty sure that they are caused by the island on Lost.
You;d have to expect that in 800,000 at least one person would forget to press the button.

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