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Magnetic declination (also called magnetic variation) is the angle between magnetic north and true north at a particular location on the Earth's surface. The angle can change over time due to polar wandering .
If the Earth's magnetic fields were exactly dipolar, the north pole of a magnetic compass needle would point directly at the North Geomagnetic Pole. In practice, it does not because the geomagnetic field that originates in the core has a more complex non-dipolar part, and magnetic anomalies in the Earth's crust also contribute to the local ...
British explorer Sir James Clark Ross discovered the magnetic north pole in 1831 in northern Canada, approximately 1,000 miles (1,609 kilometers) south of the true North Pole.
The Earth's Magnetic North Pole is actually considered the "south pole" in terms of a typical magnet, meaning that the north pole of a magnet would be attracted to the Earth's Magnetic North Pole. [2] The north magnetic pole moves over time according to magnetic changes and flux lobe elongation [3] in the Earth's outer core. [4]
The Earth's magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate—10 kilometres (6.2 mi) per year at the beginning of the 1900s, up to 40 kilometres (25 mi) per year in 2003, [26] and since then has only accelerated. [51] [52]
Over the past 150 years, the magnetic North Pole has casually wandered 685 miles across northern Canada. But right now it’s racing 25 miles a year to the northwest.
If the reference direction is north (either true north, magnetic north, or grid north), the bearing is termed an absolute bearing. In a contemporary land navigation context, true, magnetic, and grid bearings are always measured in this way, with true north, magnetic north, or grid north being 0° in a 360-degree system. [5]
Several writers proposed that the size of magnetic declination could be used to determine longitude. Mercator suggested that the magnetic north pole was an island in the longitude of the Azores, where magnetic declination was, at that time, close to zero. These ideas were supported by Michiel Coignet in his Nautical Instruction. [55]