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Based on data from: The Institute of Geophysics, ETH Zurich Archived 2007-10-31 at the Wayback Machine; Patterns in Earth's magnetic field that evolve on the order of 1,000 years Archived 2018-07-20 at the Wayback Machine. July 19, 2017; Chree, Charles (1911). "Magnetism, Terrestrial" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 17 ...
The magnetic field of a magnetic dipole has an inverse cubic dependence in distance, so its order of magnitude at the earth surface can be approximated by multiplying the above result with (R outer core ⁄ R Earth) 3 = (2890 ⁄ 6370) 3 = 0.093 , giving 2.5×10 −5 Tesla, not far from the measured value of 3×10 −5 Tesla at the equator.
The earliest ideas on the nature of magnetism are attributed to Thales (c. 624 BC – c. 546 BC). [1] [2] In classical antiquity, little was known about the nature of magnetism. No sources mention the two poles of a magnet or its tendency to point northward. There were two main theories about the origins of magnetism.
Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism.
Before magnetism was well understood, the north-seeking pole of a magnet was defined to have the north designation, according to their use in early compasses. However, opposite poles attract, which means that as a physical magnet, the magnetic north pole of the Earth is actually on the southern hemisphere.
Doctors and specialists at the Murdoch Children's Research Institute in Melbourne, Australia, are studying and reprogramming the potential of the blood to treat heart failure in children.
The thin parts are the oceanic crust, which underlies the ocean basins (5–10 km) and is mafic-rich [9] (dense iron-magnesium silicate mineral or igneous rock). [10] The thicker crust is the continental crust , which is less dense [ 11 ] and is felsic -rich (igneous rocks rich in elements that form feldspar and quartz ). [ 12 ]
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