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:
“The Mississippi, the Ganges, and the Nile,... the Rocky Mountains, the Himmaleh, and Mountains of the Moon, have a kind of personal importance in the annals of the world.”
—Henry David Thoreau (1817–1862)
“The moment Germany rises as a great power, France gains a new importance as a cultural power.”
—Friedrich Nietzsche (1844–1900)
“For even satire is a form of sympathy. It is the way our sympathy flows and recoils that really determines our lives. And here lies the vast importance of the novel, properly handled. It can inform and lead into new places our sympathy away in recoil from things gone dead. Therefore the novel, properly handled, can reveal the most secret places of life: for it is the passional secret places of life, above all, that the tide of sensitive awareness needs to ebb and flow, cleansing and freshening.”
—D.H. (David Herbert)