Change of Declination in Time and Space
Simply speaking, true north is the direction in which the north pole is located along the Earth's rotational axis, while magnetic north is the direction toward which the compass needle points.
Magnetic declination varies both from place to place and with the passage of time. As a traveller cruises the east coast of the United States, for example, the declination varies from 20 degrees west (in Maine) to zero (in Florida), to 10 degrees east (in Texas), meaning a compass adjusted at the beginning of the journey would have a true north error of over 30 degrees if not adjusted for the changing declination. In the UK it is one degree 34 minutes west (London), and as the country is quite small that figure is fairly good for the whole of the country. It is reducing, and in about 2050 it will be zero.
In most areas, the spatial variation reflects the irregularities of the flows deep in the earth; in some areas, deposits of iron ore or magnetite in the Earth's crust may contribute strongly to the declination. Similarly, secular changes to these flows result in slow changes to the field strength and direction at the same point on the Earth.
The magnetic declination in a given area may (most likely will) change slowly over time, possibly as little as 2–2.5 degrees every hundred years or so, depending upon how far from the magnetic poles it is. For a location closer to the pole like Ivujivik, the declination may change by 1 degree every three years. This may be insignificant to most travellers, but can be important if using magnetic bearings from old charts or metes (directions) in old deeds for locating places with any precision.
Read more about this topic: Magnetic Declination
Famous quotes containing the words change of, change, time and/or space:
“Comets, importing change of times and states,
Brandish your crystal tresses in the sky.”
—William Shakespeare (1564–1616)
“No change in musical style will survive unless it is accompanied by a change in clothing style. Rock is to dress up to.”
—Frank Zappa (1940–1994)
“Who first seduc’d them to that fowl revolt?
Th’ infernal Serpent; he it was, whose guile
Stird up with Envy and Revenge, deceiv’d
The Mother of Mankinde, what time his Pride
Had cast him out from Heav’n, with all his Host
Of Rebel Angels,”
—John Milton (1608–1674)
“The woman’s world ... is shown as a series of limited spaces, with the woman struggling to get free of them. The struggle is what the film is about; what is struggled against is the limited space itself. Consequently, to make its point, the film has to deny itself and suggest it was the struggle that was wrong, not the space.”
—Jeanine Basinger (b. 1936)