Magnetic fields. Magnetic field of a planet (Earth) Dipole Higher orders Short period variations Secular variations Polar drift Paleomagnetism Magnetic fields of other planets Remnant fields Reference: Physics of the Earth, F. D. Stacey & P. M. Davis, Cambridge University Press, 2008.
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Physics of the Earth, F. D. Stacey & P. M. Davis, Cambridge University Press, 2008
Image: NOAA/NGDC & CIRES
It was attributed to a effluvium in Greece or qi in China which was essentially a life energy
Initially only the horizontal orientation (declination) was used for navigation
The magnetic declination i.e. the deviation of the magnetic poles from the geographic poles was recognised and applied in navigation maps in the 16th century
The inclination of the magnetic field was confirmed in the 16th century but still was disputed later on
At 1600 the magnetic field of spherical lodestones was described as a quadrupole field (W. Gilbert, De Magnete, 1600, ISBN-10: 048626761X )
Secular variations were reported from the 15-16th century on
The magnetic field as an internal field was confirmed not before the early 20th century and was contested by e.g. Einstein until 1940Historical
Right: De Magnete 1628 Edition
Electrical conductivity map of earth mantle. Image: Anna Kelbert, Oregon State University 2009
Image: MPS, M. Fränz