posted on Mar, 18 2008 @ 02:35 PM
More on the Pole Shift from Dr. David P. Stern...
The magnetic field of the Earth changes all the time, and yes, magnetic charts have to be redrawn from time to time (this was first found in 1641, by
an Englishman named Gellibrand). And yes, in the century and a half since the first careful mapping of the Earth's field, the dipole has become
weaker by about 8% (the rate may have speeded up in 1970). If you draw a straight line through the points, you will find that perhaps 1200 years from
now, the line goes through zero.
Extending straight lines too far beyond the present, however, is risky business, as noted by no less a scientific authority than Mark Twain. In "Life
on the Mississippi" Twain noted that the Mississippi river was getting progressively shorter (mainly by floods--and by people--creating shortcuts
through bends in the river) and he wrote:
"Now, if I wanted to be one of those scientific people, and "let on" to prove what had occured in the remote past by what had occured in a
given time in the recent past, or what will occur in the far future by what has occured in late years, what an opportunity is here! ... Please
In the space of one hundred and seventy six years the lower Mississippi has shortened itself two hundred and forty-two miles. That is an average
over a mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the lower Oolitic Silurian Period, just a
million years ago next November, the lower Mississippi was upward of one million three hundred thousand miles long, and stuck out over the Gulf of
Mexico like a fishing rod. And by the same token any person can see that seven hundred and forty years from now the lower Mississippi will be only a
mile and three quarters long, and Cairo and New Orleans will have joined their streets together, and will be plodding comfortably along under a single
mayor... There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment in fact."
It is not impossible that the magnetic field will go through zero 1200 years from now, but (judging by the past record of reversals) not likely. In
any case, the field is not going away: a "flux preservation theorem" suggests this is not happening (at least not on the relatively fast time scale
of observed variations of the field; see here). In agreement with that theorem, one finds that while the dipole field is getting weaker, the
complicated parts are getting stronger. That's why I wrote "yes and no." During a reversal the two-pole (dipole) component of the field (which now
dominates it) may go through zero, but the complex parts of the field will be relatively high, and because of them, while the overall field will be
weaker, it won't vanish.
I don't know about migrating animals (they may have magnetic organs, sort of built-in compasses), but there seem to exist no magnetic effects on DNA,
resistance to antibiotics and so on; those changes seem more related to chemistry.
Finally, be cautious with compass readings in your house. Houses do contain electric currents and machinery, and these may affect the readings of a
magnetic compass. On NASA's satellites the magnetic sensor usually sits at the end of a long boom, to keep it away from interfering electric currents
in the satellite's circuits.
Keep up your interest in science!