Beyond The Atmosphere
Earth has a magnetic field that extends tens of thousands of kilometers into space and shields Earth from most of the solar wind, a stream of particles emitted by the Sun. Sudden enhancements in the solar wind, such as a surge of particles ejected by an eruption in the Sun's atmosphere, may disrupt the magnetic field, temporarily interrupting long-range radio communications and creating brilliant displays of aurorae near the poles, where the magnetic field lines bring the charged particles close to the earth's surface.
Farther out, at a mean distance of about 248,400 mi (400,000 km), is Earth's only natural satellite, the Moon. Some scientists feel that the earth and the Moon should properly be considered a "double planet," since the Moon is larger relative to our planet than the satellites of most other planets.
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