Importance
The Earth is largely protected from the solar wind, a stream of energetic charged particles emanating from the Sun, by its magnetic field, which deflects most of the charged particles. These particles would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays. Calculations of the loss of carbon dioxide from the atmosphere of Mars, resulting from scavenging of ions by the solar wind, are consistent with a near-total loss of its atmosphere since the magnetic field of Mars turned off.
The polarity of the Earth's magnetic field is recorded in sedimentary rocks. Reversals of the field are detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals allows paleomagnetists to track the past motion of continents (the study of past magnetic field is known as paleomagnetism). Reversals also provide the basis for magnetostratigraphy, a way of dating rocks and sediments. The field also magnetizes the crust; magnetic anomalies can be used to search for ores.
Humans have used compasses for direction finding since the 11th century A.D. and for navigation since the 12th century.
Read more about this topic: Earth's Magnetic Field
Famous quotes containing the word importance:
“A toothache, or a violent passion, is not necessarily diminished by our knowledge of its causes, its character, its importance or insignificance.”
—T.S. (Thomas Stearns)
“Shall we then judge a country by the majority, or by the minority? By the minority, surely. ‘Tis pedantry to estimate nations by the census, or by square miles of land, or other than by their importance to the mind of the time.”
—Ralph Waldo Emerson (1803–1882)
“The importance of a lost romantic vision should not be underestimated. In such a vision is power as well as joy. In it is meaning. Life is flat, barren, zestless, if one can find one’s lost vision nowhere.”
—Sarah Patton Boyle, U.S. civil rights activist and author. The Desegregated Heart, part 1, ch. 19 (1962)