Does the Earth's magnetic field really reverse every few thousand years?

AI Thread Summary
The Earth's magnetic field does change and the poles are in constant motion, necessitating regular recalibration of magnetic compasses. Geological evidence supports the idea that the magnetic field reverses periodically, although the exact cause of these reversals remains unclear. The shifting of iron within the Earth is believed to play a role in this phenomenon. Research by Dr. Daniel Lathrop from the University of Maryland provides insight into these magnetic dynamics. Understanding the mechanisms behind the magnetic field and its reversals is still an area of active study.
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I heard that the Earth's magnetic field changes every few thousands of years? is this true, if it is how does that happen
 
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The Earth's magnetic poles are in constant motion, moving in distances easily measured in just a year. This is the reason why magnetic compasses readings must be recalibrated over time.

I believe the best answer available today is that this is caused by some sort of shifting of the iron inside of earth.
 
There is indeed geological evidence that the Earth's magnetic field reverses periodically. The cause for the reversal is not really understood, neither the cause for the field itself. There is a thread about ithere .

The thread is largely based on the work of Dr. Daniel Lathrop of University of Maryland.http://complex.umd.edu/dynamo/index.html .
 
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Susskind (in The Theoretical Minimum, volume 1, pages 203-205) writes the Lagrangian for the magnetic field as ##L=\frac m 2(\dot x^2+\dot y^2 + \dot z^2)+ \frac e c (\dot x A_x +\dot y A_y +\dot z A_z)## and then calculates ##\dot p_x =ma_x + \frac e c \frac d {dt} A_x=ma_x + \frac e c(\frac {\partial A_x} {\partial x}\dot x + \frac {\partial A_x} {\partial y}\dot y + \frac {\partial A_x} {\partial z}\dot z)##. I have problems with the last step. I might have written ##\frac {dA_x} {dt}...
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Thread 'Griffith, Electrodynamics, 4th Edition, Example 4.8. (Second part)'

I am reading the Griffith, Electrodynamics book, 4th edition, Example 4.8. I want to understand some issues more correctly. It's a little bit difficult to understand now. > Example 4.8. Suppose the entire region below the plane ##z=0## in Fig. 4.28 is filled with uniform linear dielectric material of susceptibility ##\chi_e##. Calculate the force on a point charge ##q## situated a distance ##d## above the origin. In the page 196, in the first paragraph, the author argues as follows ...
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