Van Allen Discovers the Earth’s Radiation Belts (Great Events from History II: Science and Technology Series)
Article abstract: Van Allen pioneered the use of artificial satellites for earth studies, which led to the discovery of electrically charged particles trapped within the earth’s magnetic field.
Summary of Event
William Gilbert, English physician and physicist, wrote in 1600 that Earth has a magnetic field similar to a bar magnet. He reported that a compass points roughly north and south and that it is the magnetic poles of the earth’s magnet that attract the compass needle. Because the magnetic field has two poles, it is a dipole field, as opposed to a monopole field, of an electrically charged particle.
Other research over the centuries has increased an understanding of the magnetic field. Roughly 95 percent of the field is the result of sources deep within the interior of the earth, while the remainder is attributable to electrical currents in the upper atmosphere and other sources in space. The poles are not stationary, but wander over the face of the earth. The poles are currently located in the islands north of Canada. It can be inferred, therefore, that the interior source is not a permanent bar magnet but rather a dynamo effect...
(The entire section is 1938 words.)
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