Scientists understand that Earth's magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years ago, and facing what we call north with a magnetic compass in your hand, the needle would point to 'south.' This is because a magnetic compass is calibrated based on Earth's poles. The N-S markings of a compass would be 180 degrees wrong if the polarity of today's magnetic field were reversed. Many doomsday theorists have tried to take this natural geological occurrence and suggest it could lead to Earth's destruction. But would there be any dramatic effects? The answer, from the geologic and fossil records we have from hundreds of past magnetic polarity reversals, seems to be 'no.'

Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. Magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. Scientists estimate reversals have happened at least hundreds of times over the past three billion years. And while reversals have happened more frequently in "recent" years, when dinosaurs walked Earth a reversal was more likely to happen only about every one million years.

Sediment cores taken from deep ocean floors can tell scientists about magnetic polarity shifts, providing a direct link between magnetic field activity and the fossil record. The Earth’s magnetic field determines the magnetization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart. As the lava solidifies, it creates a record of the orientation of past magnetic fields much like a tape recorder records sound. The last time that Earth's poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal. The fossil record shows no drastic changes in plant or animal life. Deep ocean sediment cores from this period also indicate no changes in glacial activity, based on the amount of oxygen isotopes in the cores. This is also proof that a polarity reversal would not affect the rotation axis of Earth, as the planet's rotation axis tilt has a significant effect on climate and glaciation and any change would be evident in the glacial record.

I'm outa here.

Hi Squeers,

I was interested in your juxtaposition of Finkelstein's recommendations and " .... the sheep of popular opinion."

Would you care to elaborate ?

No rush :)

Joe

Joe,
I think I made my point very clearly above, but lest anyone's inclined to label me elitist--looking down from lofty heights at popular opinion--my point was that a great many people allow themselves to be persuaded by a noisy but small cohort of minimifidianists. This fits with the argument of the article--that people "are often persuaded to believe what is already dominant or what fits their irrational needs". Or, we could add, what serves their ideological bent, or even more, what validates their lifestyle and vested interests. The "sheep of popular opinion" are those who are incapable of critical or self-reflexive thought, yet are often authoritarian and passionate, and take their lead from whatever source, however dubious, seems most supportive of them.
But really, I'm satisfied with my opinion as I put it above. Is there anything in it you differ with?

Hi Squeers,

I guess that's a consequence of living in a democracy, where people are free to speak rubbish as well as brilliant truth, and where there is NOBODY who dictates which is which.

And if freedom of speech exists in a democracy, then so does its written expression. Yes, it might be rubbish, what newspapers publish. Yes, dumb-@rses may be persuaded by what they hear and read but again, who decides what they should or shouldn't hear and read ? Judges ? Public intellectuals ? God help us.

I don't know how you get around calling that controlling approach 'elitist'. As Salman Rushdie has said often, and been penalised for it, the right of free speech is worth nothing if it does not include the right to offend. Of course, the laws on free speech come up against the laws against slander. In case of freedom of the press, any extension of the right to spout offensive rubbish (and the right to listen to it and be persuaded by it) into print confronts the laws on libel.

And where would some of us be if we were not allowed to spout rubbish on OLO ? What would we do all day ?

Yes, the shock-jocks and the gutter press often promote distorted versions of the truth, to put it mildly. But to paraphrase the old WW I joke, if you know of better arguments, then put them forward. The worst thing we can do in these sorts of situations is to rely on some puffed-up, self-promoting 'public intellectual' to do our thinking for us.

If you have an alternative point of view of your own, then put it. Try to get it published somewhere. That's the value of an institution like OLO: we can take the mickey out of each other, and out of anybody who purports to be a 'public intellectual'.

Thank god for that good old-fashioned Australian disrespect for anybody who gets too far up themselves. May it long continue.

And we're not as sheep-like as you may think :)

Cheers,

Joe