From Free net encyclopedia
- This article is about the geographic meaning of "North Pole." For the cities, see North Pole, Alaska and North Pole, New York. For the UK depot of Eurostar, see North Pole depot. For the astronomical use of the term "circumpolar," see circumpolar constellation.
Geographic North Pole
The Geographic North Pole, also known as True North, is close to the northern point at which the Earth's axis of rotation meets the surface. Geographic North defines latitude 90° North. In whichever direction you travel from here, you are always heading south. The pole is located in the Arctic Ocean. Classically (19th century) this pole was exactly where people believed the pole of rotation met the Earth's surface, but soon astronomers noticed a small apparent variation of latitude as determined for a fixed point on Earth by observing stars. This variation had a period of about 435 days and the periodic part of it is now called the Chandler wobble after its discoverer. It is desirable to tie the system of Earth coordinates (latitude, longitude, and elevations or orography) to fixed landforms. Of course, given continental drift and the rising and falling of land due to volcanos, erosion and so on, there is no system in which all geographic features are fixed. Yet the International Earth Rotation and Reference Systems Service and the International Astronomical Union have defined a framework called the International Terrestrial Reference System that does an admirable job. The North pole of this system now defines geographic North and it does not quite coincide with the rotation axis. Also see polar motion.
On the basis of the sector principle, Canada claims its sovereignty to extend all the way to the Geographic North Pole. There is no land at this location, which is usually covered by sea ice. The theory under which Canada has claimed sovereignty to the North Pole is controversial as there is in fact 770 km of ocean between the pole and Canada's northernmost land point, and several nations, most notably the United States, have challenged the notion that the North Pole does not lie in international waters.
Defining the North Pole of Earth
The North Pole can be defined in four different ways. Only the first two definitions are commonly used.
However it is defined, the North Pole lies in the Arctic Ocean. Unlike its antipode, the South Pole, it lies not on a polar continent (Antarctica means anti-, i.e. opposite, Arctis, the northern polar region), nor is it part of any (sub)continent or island, so there is no land, just (almost) permanently frozen waters.
- The Geographic North Pole, also known as True North, is approximately the northern point at which the Earth's axis of rotation meets the surface. (see next section)
- The Magnetic North Pole is the northern point at which the geomagnetic field points vertically, i.e. the dip is 90°.
- The Geomagnetic North Pole is the pole of the Earth's geomagnetic field's dipole moment (somewhat confusingly, it is technically the south pole of the dipole).
- The Northern Pole of Inaccessibility is defined as the point in the Arctic farthest from any coastline, and is at Template:Coor dm. Similar poles exist in the Pacific and Indian oceans, and there is a dry land pole of inaccessibility in the Antarctic.
The first expedition to the pole is generally accepted to have been made on April 6, 1909 by Anglo-American Navy engineer Robert Edwin Peary, African-American Matthew Henson, and four Inuit men named Ootah, Seegloo, Egingway, and Ooqueah. Polar historians believe that Peary honestly thought he had reached the pole. However a 1996 analysis of a newly-discovered copy of Peary's record indicates that Peary must have been in fact 20 nautical miles (40 km) short of the Pole.
The first undisputed sight of the pole was on May 12 1926 by Norwegian explorer Roald Amundsen and his American sponsor Lincoln Ellsworth from the airship Norge. Norge, though Norwegian owned, was designed and piloted by the Italian Umberto Nobile. The flight started from Svalbard and crossed the icecap to Alaska. Nobile, along with several scientists and crew from the Norge overflew the Pole a second time on May 24 1928 in the Airship Italia.
The United States Navy submarine USS Nautilus (SSN-571) crossed the North Pole on August 3, 1958, and on March 17, 1959, the USS Skate (SSN-578) surfaced at the pole, becoming the first naval vessel to reach it.
Magnetic North is one of several locations on the Earth's surface known as the "North Pole". Its definition, as the point where the geomagnetic field points vertically downwards, i.e. the dip is 90°, was proposed in 1600 by Sir William Gilbert, a courtier of Queen Elizabeth I, and is still used. It should not be confused with the less frequently used Geomagnetic North Pole. Magnetic North is the place to which all magnetic compasses point, although since the pole marked "N" on a bar magnet points north, and only opposite magnetic poles are attracted to each other, the Earth's magnetic north is actually a south magnetic pole.
The orientation of magnetic fields of planets can flip over, an event which is called a geomagnetic reversal. The Earth's poles have done this repeatedly throughout history, and 500,000 years ago, the south magnetic pole was at the South Pole. It is thought that this occurs when the circulation of liquid nickel/iron in the Earth's outer core is disrupted and then reestablishes itself in the opposite direction. It is not known what causes these disruptions. Proof of this can be seen at mid-ocean ridges where tectonic plates move apart, and the sea bed is filled in with magma. As the magma comes out of the mantle, the magnetic particles in it are attracted slightly to the North Pole, and when the poles switch, so does the direction in which the metallic elements face. Therefore, on the sea bed, parallel bands of alternating magnetic fields are found.
The first expedition to reach this pole was led by James Clark Ross, who found it at Cape Adelaide on the Boothia Peninsula on June 1, 1831. Roald Amundsen found Magnetic North in a slightly different location in 1903. The third observation of Magnetic North was by Canadian government scientists Paul Serson and Jack Clark, of the Dominion Astrophysical Observatory, who found the pole at Allen Lake on Prince of Wales Island.
The Canadian government has made several measurements since, which show that Magnetic North is continually moving northwest. In 1996 an expedition certified its location by magnetometer and theodolite at 78°35.7' North, 104° 11.9' West. Its location (in 2005) is 82°07' North, 114° 04' West, near Ellesmere Island, the biggest of the Queen Elizabeth Islands, in Canada. During the 20th century it has moved 1100 km, and since 1970 its rate of motion has accelerated from 9 km/year to 41 km/year (2001-2003 average; see also Polar drift). If it maintains its present speed and direction it will reach Siberia in about 50 years, but it is expected to veer from its present course and slow down.
This movement is on top of a daily or diurnal variation in which Magnetic North describes a rough ellipse, with a maximum deviation of 80 km from its mean position. This effect is due to disturbances of the geomagnetic field by the sun. A line drawn from one magnetic pole to the other does not go through the centre of the Earth; it actually misses it by about 530 km.
The angular difference between Magnetic North and true North varies with location, and is called the magnetic declination.
Geomagnetic North Pole
The Geomagnetic North Pole is the pole of the Earth's geomagnetic field closest to true north. The first-order approximation of the Earth's magnetic field is that of a single magnetic dipole (like a bar magnet), tilted about 11° with respect to Earth's rotation axis and centered at the Earth's core. The residuals form the nondipole field. The Geomagnetic poles are the places where the axis of this dipole intersects the Earth's surface. Because the dipole approximation is far from a perfect fit to the Earth's magnetic field, the magnetic field is not quite vertical at the geomagnetic poles. The locations of true vertical field orientation are the magnetic poles, and these are about 30 degrees of longitude away from the geomagnetic poles.
Like the Magnetic North Pole, the geomagnetic north pole is a south magnetic pole, because it attracts the north pole of a bar magnet. It is the centre of the region in the magnetosphere in which the Aurora Borealis can be seen. Its present location is 78°30' North, 69° West, near Qaanaaq in Greenland, however it is now drifting away from North America and toward Siberia. The first voyage to this pole was by David Hempleman-Adams in 1992.
Northern Pole of Inaccessibility
The Northern Pole of Inaccessibility, located at 84°03' north, 174°51' west, is the point farthest from any northern coastline, about 1100 km from the nearest coast. It is a geographic construct, not an actual physical phenomenon. It was first reached by Sir Hubert Wilkins, who flew by aircraft in 1927; in 1958 a Russian icebreaker reached this point.
Defining North Poles in astronomy
Astronomers define the north "geographic" pole of a planet or other object in the solar system by the planetary pole that is in the same ecliptic hemisphere as the Earth's north pole. More accurately, «The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system» . This means some objects will have directions of rotation opposite the "normal" (i.e., not counter-clockwise as seen from above the north pole). Another frequently used definition uses the right-hand rule to define the north pole: it is then the pole around which the object rotates counterclockwise . When using the first definition (the IAU's), an object's axial tilt will always be 90° or less, but its rotation period may be negative (retrograde rotation); when using the second definition, axial tilts may be greater than 90° but rotation periods will always be positive.
For the magnetic poles, their names are decided upon by the direction that their field lines emerge or enter the planet's crust. If they enter the same way as they do for Earth at the north pole, we call this the planet's north magnetic pole.
Some bodies in the solar system, including Saturn's moon Hyperion and the asteroid 4179 Toutatis, lack a stable geographic north pole. They rotate chaotically because of their irregular shape and gravitational influences from nearby planets and moons, and as a result the instantaneous pole wanders over their surface, and may vanish altogether for brief periods (when the object comes to a complete standstill with respect to the distant stars).
In the particular (but frequent) case of synchronous satellites, four more poles can be defined. They are the near, far, leading, and trailing poles. Take Io for example; this moon of Jupiter rotates synchronously, so its orientation with respect to Jupiter stays constant. There will be a single, unmoving point of its surface where Jupiter is at the zenith, exactly overhead —this is the near pole, also called the sub- or pro-Jovian point. At the antipode of this point is the far pole, where Jupiter lies at the nadir; it is also called the anti-Jovian point. There will also be a single unmoving point which is furthest along Io's orbit (best defined as the point most removed from the plane formed by the north-south and near-far axes, on the leading side) —this is the leading pole. At its antipode lies the trailing pole. Io can thus be divided into north and south hemispheres, into pro- and anti-Jovian hemispheres, and into leading and trailing hemispheres. Note that these poles are mean poles because the points are not, strictly speaking, unmoving: there is constant jiggling about the mean orientation, because Io's orbit is slightly eccentric and the gravity of the other moons disturbs it regularly.
Day and night
During the summer months, the North Pole experiences twenty four hours of daylight daily but during the winter months the North Pole experiences twenty four hours of darkness daily. Sunrise and sunset do not occur in a twenty four hour cycle. At the north pole, sunrise begins at the Vernal equinox taking three months for the sun to reach its highest point at the summer solstice when sunset begins, taking three months to reach sunset at the Autumnal equinox. A similar effect can be observed at the South Pole, with a six month difference. This day/night effect is in stark contrast to what is observed at the Equator.
This effect is caused by a combination of the Earth's axial tilt and its rotation around the sun. The direction and angle of axial tilt of the Earth remains fairly constant (on a yearly basis) in its plane of rotation around the sun. Hence during the summer, the North Pole is always facing the sun's rays but during the winter, it always faces away from the sun.
Territorial claims to the North Pole (Arctic)
In 1925, based upon the Sector Principle, Canada became the first country to extend its boundaries northward to the North Pole, at least on paper, between 60°W and 141°W longitude, a claim that is not universally recognized. In addition, Canada claims the water between its Arctic Islands as internal waters. The claim is not recognized by the United States, which argues the Northwest Passage is an international waterway, despite its minimal usage for shipping. Denmark (Greenland), Russia and Norway have made similar claims, which are also opposed by the United States and by the European Union.
Otherwise, until 1999, the North Pole and Arctic Ocean had been generally considered international territory. However, as the polar ice has begun to recede at a rate higher than expected (see global warming), several countries have made moves to claim, or to enforce pre-existing claims to, the waters or seabed at the Pole. Russia made its first claim in 2001, claiming Lomonosov Ridge, an underwater mountain ridge underneath the Pole, as a natural extension of Siberia. This claim was contested by Norway, Canada, the United States and Denmark in 2004. The Danish autonomous province of Greenland has the nearest coastline to the North Pole, and Denmark argues the Lomonosov Ridge is in fact an extension of Greenland.
The potential value of the North Pole and the area around resides not so much in shipping but in the possibility that lucrative petroleum and natural gas reserves exist below the sea floor. Such reserves are known to exist under the Beaufort Sea, and further exploration elsewhere in the Arctic might become more feasible if global warming opens up the Northwest Passage as a regular channel of international shipping and commerce, particularly if Canada is not able to enforce her claim to it.
Template:Main Magnetic north is determined by the earth’s magnetic field and is not the same as true (or geographic) north. The location of the magnetic north pole changes slowly over time, but it is currently northwest of Hudson Bay in northern Canada (approximately 700 km [450 mi] from the true north pole). Maps are based on the geographic north pole because it does not change over time, so north is always at the top of a quadrangle map. However, if you were walk a straight line following the direction your compass needle indicates as north, you would find that you didn’t go from south to north on the map.
How far your path varied from true north depends on where you started from; the angle between a straight north-south line and the line you walked is the magnetic declination in the area you were walking.
Magnetic declination has been measured throughout the U.S. and can be corrected for on your compass. The line of zero declination runs from magnetic north through Lake Superior and across the western panhandle of Florida. Along this line, true north is the same as magnetic north. If you are working west of the line of zero declination, your compass will give a reading that is east of true north. Conversely, if you are working east of the line of zero declination, your compass reading will be west of true north. The exact amount that you need to adjust the declination on your compass to reconcile magnetic north to true north is given in the map legend to the left of the map scale.
Cultural references to the North Pole
- South Pole
- Arctic Ocean
- List of firsts
- Inuit Circumpolar Conference
- Arctic Council
- Circumpolar arctic
- Arctic Council
- The Northern Forum
- North Pole scenery observed by Web Cams
- The short Arctic summer of 2004
- The puzzling Arctic summer of 2003
- FAQ on the Arctic and the North Pole
- Polar Controversies Still Rage article by Roderick Eime
- Magnetic Poles locations since 1600 Download the KMZ file. For Google Earth Users.
- The Polar Race a biennial race to the 1996 certified position of the Magnetic North Pole
- Template:ConfluenceTemplate:Link FA
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