# why earth is a magnet

## 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 Earths 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 1.1). The outer core consists of molten metals, mainly iron and nickel. Scientists think that Earths 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.

## 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 Earths 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.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

the scientist who demonstrated in 1800 that earth is a magnet was

``````a) charles darwin.

-->  b) william gilbert.

c) isaac newton.

d) marie curie.
``````

earths magnetic north pole is located at 90 degrees north latitude.

``````a. true

-->  b. false
``````

how do the lines of force move in earths magnetic field?

``````-->  a) from north to south magnetic poles

b) from south to north magnetic poles

c) in circles parallel to the equator

d) none of the above
``````

what have scientists learned about why earth is a magnet?

``````a) earths magnetism is caused by the movement of charged particles.

b) earths magnetism is generated in molten metals in the core.

c) earths magnetism occurs because the planet is spinning on its axis.

-->  d) all of the above
``````

earth has a liquid inner core and solid outer core.

``````a. true

-->  b. false
``````

## diagram questions

No diagram questions associated with this lesson