Earth’s Magnetic Field

Earth’s Magnetic Field

Here’s a question for you: Which has a stronger magnetic field, the world’s largest magnet, or the one that’s holding a photograph to your refrigerator? It’s a trick question. And for extra credit what is a Chron? I’m Jim Metzner and this is the Pulse of the Planet. The world’s largest magnet is the earth itself, and it plays an important role in helping to support life on earth. As for its strength, we asked astronomer Bob Berman.

Berman: “Earth’s magnetic field is about 100 times weaker than that of an ordinary refrigerator magnetic, but it has the effect of channeling cosmic rays around us and acting as a kind of safety shield for some of the cosmic radiation that comes from the universe.”

Like any magnet, the earth has a north and south pole, and their locations are shifting all the time.

“The poles are changing their locations at a unprecedented rate. They used to move 5 miles a year, but they’ve been moving 37 miles a year for most of the last century, and nobody knows why. And then, once, on average, every 780,000 years, they flip over. North becomes south; south becomes north. A period of time where the magnetic polarity stays the same is called a Chron. Now, a Chron can last as little as a few tens of thousands of years, or it could last as long as 40 or 50 million years. And we know that it changes because all we have to do is dig down and look at different rocks that contain ferromagnetic materials, because as lava solidifies, any iron in it will line up with the prevailing field of Earth. And so, we know exactly what Earth’s magnetic field was going back in time, and we have found about 150 instances of flips.”

Bob Berman is the author of the Sun’s Heartbeat. I’m Jim Metzner and this is the Pulse of the Planet.

Earth's Magnetic Field

The earth's magnetic field is weakening and the poles are changing locating and - every 780,000 years or so, flipping!
Air Date:07/17/2015
Scientist:
Transcript:

Earth's Magnetic Field

Here's a question for you: Which has a stronger magnetic field, the world's largest magnet, or the one that's holding a photograph to your refrigerator? It's a trick question. And for extra credit what is a Chron? I'm Jim Metzner and this is the Pulse of the Planet. The world's largest magnet is the earth itself, and it plays an important role in helping to support life on earth. As for its strength, we asked astronomer Bob Berman.

Berman: "Earth's magnetic field is about 100 times weaker than that of an ordinary refrigerator magnetic, but it has the effect of channeling cosmic rays around us and acting as a kind of safety shield for some of the cosmic radiation that comes from the universe."

Like any magnet, the earth has a north and south pole, and their locations are shifting all the time.

"The poles are changing their locations at a unprecedented rate. They used to move 5 miles a year, but they've been moving 37 miles a year for most of the last century, and nobody knows why. And then, once, on average, every 780,000 years, they flip over. North becomes south; south becomes north. A period of time where the magnetic polarity stays the same is called a Chron. Now, a Chron can last as little as a few tens of thousands of years, or it could last as long as 40 or 50 million years. And we know that it changes because all we have to do is dig down and look at different rocks that contain ferromagnetic materials, because as lava solidifies, any iron in it will line up with the prevailing field of Earth. And so, we know exactly what Earth's magnetic field was going back in time, and we have found about 150 instances of flips."

Bob Berman is the author of the Sun's Heartbeat. I'm Jim Metzner and this is the Pulse of the Planet.