Figure 24.5: The force of gravity exists between all objects in the universe; the strength of
the force depends on the mass of the objects and the distance between them. ( 20 )
Earth’s Magnetism
Earth has amagnetic field(Figure24.6). It may be helpful to imagine that the Earth
has a gigantic bar magnet inside of it. A bar magnet has a north and south pole and a
magnetic field that extends around it. Earth’s magnetic field also has a north and south
pole and a magnetic field that surrounds it. Scientists believe Earth’s magnetic field arises
from the movements of molten metals deep inside Earth’s outer liquid iron core. Iron and
nickel flow within the Earth’s core, and their movement generates Earth’s magnetic field.
Earth’s magnetic field extends several thousand kilometers into space.
Earth’s magnetic field serves an important role. It shields the planet from harmful types of
radiation from the Sun (Figure24.7). If you have a large bar magnet, you can tie a string
to it, hang it from the string, and then watch as it aligns itself in a north-south direction, in
response to Earth’s magnetic field. This concept allows a compass to work, so that people
can navigate by finding magnetic north (Figure24.8).
Lesson Summary
- The Earth and other planets in our solar system are rotating spheres, that also revolve
around the Sun in fixed paths called orbits. - The inner four planets are small, dense rocky planets like Earth. The next four planets
are large, gaseous planets like Jupiter. - The balance between gravity and our motion around the Sun, keep the planets in orbit
at fixed distances from the Sun. - Earth has a magnetic field, created by motion within Earth’s outer, liquid iron core
that shields us from harmful radiation.