What Makes Earth a Magnetic Force?

Podcast

What Makes Earth a Magnetic Force?

Transcript

What makes the earth a magnetic force? I'm Bob Hirshon and this is Science Update.

Migrating birds and ships at sea rely on the earth's magnetic field to tell north from south. Listener Matt Zimmerman of Washington, DC wanted to know why we have a magnetic field in the first place.

We spoke to Greg Lyzenga, a physicist at Harvey Mudd College, and he says scientists are asking the same question. They're searching for answers by looking into outer space.

Lyzenga:
"We look at the other bodies of the solar system and in the universe that also have magnetic fields. They also have a molten core and it's electrically conducting. And so the magnetic field of planets like the earth is caused by the circulation of electrically conducting material."

Dr. Lyzenga says that that molten material is iron, a magnetic metal. But at the high temperatures inside the planets, iron loses its magnetism. So exactly why it's acting like a giant bar magnet is a mystery.

Whatever the cause, we're lucky it happens. The earth's magnetic field shields us from deadly radiation from the sun. So if it weren't there, we probably wouldn't be around to wonder about it.

If you're pulled toward science mysteries, call us at 1-800-WHY-ISIT. If we use it on the show you'll get a free Science Update Mug. For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

Think about the earth's magnetic field, and ways in which it is used by people and animals. Continue your exploration of earth's magnetic field by learning about how the fields flip their polarity at regular intervals.

Now try to answer the following questions:

1. Why does the cause of the earth's magnetic field remain a mystery?
2. What would happen to the earth if this magnetic force did not exist?
3. What have scientists learned about the source of the earth's magnetic field by looking at other bodies in the solar system?
4. Can you identify other bodies in the solar system that have a magnetic field?
5. How is the earth's magnetic field used by people and animals?

Going Further

For more information on magnetic fields, go to: Ask a Scientist from NASA, or visit the Nine Planets website.

For a hands-on activity related to magnetic fields, go to: The Stanford Solar Center.

The National High Magnetic Field Laboratory website has an Science, Magnets & You guidebook for primary grades that provides information and activities to help students understand magnets and magnetic fields.