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The Earth is a huge electromagnet, and according to the laws of physics, Earth’s magnetic field should just decay over time. So, why doesn’t it? I’m Jim Metzner, and this is the Pulse of the Planet.
“The magnetic field of the Earth is not a big, permanent magnet because the temperature’s way too high, and so, if you didn’t have some process, some mechanism, to keep regenerating the field, that magnetic field would just naturally decay away. And the time scale for that is about 20,000 years. 20,000 years sounds like a long time, but it’s a short time compared to the age of the Earth and compared to how long the magnetic field’s been around.”
Gary Glatzmaier is a Professor at University of California in Santa Cruz.
“So, there must be some mechanism down there that’s always regenerating the field and replacing the part of the field that decays away, and the mechanism appears to be this fluid motion in the outer core that’s generating large electric currents and the associated magnetic fields with it.”
Deep within the Earth, a molten outer core is in constant motion, amidst Earth’s existing magnetic field.
“You have this fluid motion in the core moving through a magnetic field and generating large electric currents, and, you know, basic laws of physics say that if you have a large electric current, you have a magnetic field around it. And this magnetic field is a new magnetic field that’s generated that’s trying to replace the old magnetic field.”
And in future programs, we’ll find out why the intensity and direction of Earth’s magnetic field has changed dramatically over time.
Pulse of the Planet is made possible by the National Science Foundation. I’m Jim Metzner.
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