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Rounding the southern coast of Africa in the 1480s and 1490s, Portuguese navigators discovered one point where magnetic north and true north were virtually identical. They called this place the "Cape of the Needles" (Cabo das Agulhas) because all compass needles pointed to true north. |
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Cape Agulhas, the southern most point of the African continent today |
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Earth's Magnetic Field The
earth's magnetic field results from a spinning molten metallic core.
The concentration of metal in the northern part of the hemisphere
means that compass needles will point generally, but no t exactly,
north. The difference between true north and magnetic north is called
"magnetic deviation" (to distinguish it from other possibly deviant
activities).
Changes in Magnetic Fields Because the core is spinning in a
different direction than the rest of the earth, there are inevitable
regional shifts in the earth's magnetic fields, even though the great
concentration remains stable in the north.
Electromagnetic Storms The earth's regular magnetic patterns are sometimes suddenly disrupted by sudden magnetic storms caused by energy flaring out of the usn. The earth's magentic fields sometimes trap huge plasma bubbles traveling at 500 miles a second from the sun, causing power outages, radiation exposure, and inaccurate magnetic readings.
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