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Why Earth Is a Magnet

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Why Earth Is a Magnet

Did you ever see a globe like this one? Magnets in the globe and its stand repel each other, allowing the globe to hover in midair. The globe is a good model for Earth the magnet.  

Earth the Magnet

Like the real Earth, the globe pictured above is a magnet. A magnet is an object that has north and south magnetic poles and a magnetic field. The magnetic globe is a modern device, but the idea that Earth is a magnet is far from new. It was first proposed in 1600 by a British physician named William Gilbert. He used a spherical magnet to represent Earth. With a compass, he demonstrated that it the spherical magnet causes a compass needle to behave the same way that Earth causes a compass needle to behave. This showed that a spherical magnet is a good model for Earth and therefore that Earth is a magnet.

Q: Can you describe Earth’s magnetic poles and magnetic field?

A: Earth has north and south magnetic poles. The North Pole is located at about 80 degrees north latitude. The magnetic field is an area around Earth that is affected by its magnetic field. The field is strongest at the poles, and 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 the Figure below ). 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

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.

Practice

At the following URL, watch the video to gain a deeper understanding of the production of Earth’s magnetic field. Then write three points that extend the content of this article.

http://www.youtube.com/watch?v=8_P4WpxUYq4

Review

  1. How did Gilbert show that Earth is a magnet?
  2. Which would be a better model of Earth’s inner structure: a peach or an orange? Explain your answer?
  3. Explain why Earth generates a magnetic field.

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