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| Centuries before Copernicus proposed the geocentic model of the solar system, the early Chinese discovered the use of a compass for navigation. Early Greeks had also found that a steel needle stroked with a rare stone (lodestone) that attracted iron also had this strange power. Magnetic force and knowledge of magnetism has been studied for at least 500 years. A more formal study of magnetism began when Sir William Gilbert wrote the first scientific paper describing a compass needle’s direction as being due to the Earth behaving like it was a large bar magnet. In 1634 Gellibrand discovered that the direction of the Earth’s magnetic field varied. Following this discovery in the 1740’s George Graham in London and Anders Celcius in Sweden found that the variations correlated with auroural displays. Later in 1805 Baron von Humbolt noted these disturbances and called them “magnetic storms” for the first time. In 1821 in Copenhagen, Hans C. Oersted made the critical discovery that a flow of electricity made a compass needle deflect from pointing towards north. Oersted could not explain this phenomena, but at about the same time in France, Andre-Marie Ampere found that two wires with current flowing interact magnetically. The connection between magnetism and electricity was further demonstrated by James Clerk Maxwell and extended with his discovery that the speed of light was also involved. This helped to lead him into the study of electromagnetic waves and the beginning of the development of modern physics. During the mid 1800’s Karl Frederick Gauss confirmed Gilbert’s hypothesis and found that this magnetic force had to be caused somewhere within the Earth, not externally. Early on people recognized the value of this information by using magnetic force to locate valuable ore deposits. In 1859 Richard Carrington correlated the eruption near a sunspot with a large magnetic storm 17 hours later. This was the first recorded connection between the Sun and magnetic changes near the Earth. Michael Faraday used a compass and traced the direction of the needle to make a visualization of magnetic field lines for the first time in 1864. James Clerk Maxwell expanded on this idea mathematically and called this space an electromagnetic field for the first time. The early 1900’s found Kristian Birkeland experimenting with beams of electrons to further investigate magnetic fields. He found these negatively charged beams were attracted to the areas near magnetic poles, leading him to suggest this as the cause of polar auroras. This was later disproved (1930-1931) by Sydney Chapman and Vincent Ferraro in England. They proposed that magnetic storms were caused by envelopment of the Earth by plasma clouds ejected from the Sun. Today these magnetic fields have been better described. In space, on the Sun and inside the Earth, it is known that these magnetic fields are caused by electric currents. The movement of free electrons and ions in space can be shown to follow magnetic field lines. After 1959, a year after the launch of Explorer satellites 1 and 3 found definitive proof of the radiation belt around the Earth, the term magnetosphere was used by Thomas Gold of Cornell University. Shortly afterwards, in 1961, James Dungey in Britian suggested that solar wind energy was transmitted by direct magnetic linkage to the magnetosphere. This led to further studies using satellites (see list below) to refine and trace the Earth’s Magnetosphere as seen below. Magnetism & Field Lines. The Earth's Magnetosphere at http://www-spof.gsfc.nasa.gov/Education/wms2.html
Notice that due to the solar wind the Earth’s magnetosphere is not symmetrical like the field around a bar magnet.
A printable student construction; Folding Magnetosphere Model can be found at
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