http://www.ck12.org Chapter 5. Energy
lines of magnetic force move from the north to the south magnetic pole.
Spinning Like a Top
Although the idea that Earth is a magnet is centuries old, the discovery of why Earth is a magnet is a relatively new.
In the early 1900s, scientists started using seismographic data to learn about Earth’s inner structure. A seismograph
detects and measure earthquake waves. Evidence from earthquakes showed that Earth has a solid inner core and a
liquid outer core (see theFigure5.179). The outer core consists of molten metals, mainly iron and nickel. Scientists
think that Earth’s magnetic field is generated by the movement of charged particles through these molten metals in
the outer core. The particles move as Earth spins on its axis. The video at the URL below takes a closer look at how
this occurs.
http://www.youtube.com/watch?v=O-V3yR2RZUE
FIGURE 5.179
Summary
- In the 1600s, William Gilbert demonstrated that Earth is basically a spherical magnet, with north and south
poles and a magnetic field. - In the 1900s, scientists used earthquake data to determine that Earth has a solid inner core and molten outer
core. Scientists think that Earth is a magnet because of charged particles moving through the molten outer
core as Earth spins on its axis.
Vocabulary
- magnet: Object that attracts ferromagnetic materials such as iron.