ARI SHAPIRO, HOST:
Sometimes it's great to have an astrophysicist at your fingertips. You know what I mean? Well, we have NPR blogger Adam Frank, and we asked you to send in your big questions about physics, astronomy or science in general so that we can give you some short answers or rather so Adam can give you some short answers. Hi, Adam.
ADAM FRANK, BYLINE: Hey.
SHAPIRO: This question comes from Bob MacNeal. Adam, take it away.
FRANK: Bob asks, what accounts for the strength of Earth's magnetic field, and how does it compare to Venus and Mars. And also what about its longevity? How long does it last?
SHAPIRO: OK, Adam, let's break this down bit by bit. When I think of Earth's magnetic field, I think of - OK, we've got a North and South pole, and if you take a compass that has a little piece of metal in it, it'll point north using that magnetic field. But what is it actually?
FRANK: OK, well, basically what a magnetic field is, is it's a force. It's basically a force field which extends through space. And what's happening in the earth is that stuff happening in the core is generating that magnetic field. And you know, you can detect it with your compass, but there's much more to it. In fact one of the things that the magnetic field is doing is it's protecting us from radiation coming from the sun.
SHAPIRO: OK, let's talk about the next part of the question now, which is how Earth's magnetic field compares to Mars and Venus.
FRANK: Yeah, well, the interesting thing is neither Mars nor Venus really has much of a magnetic field at all. They're thousands of times or more weaker than the Earth's field.
SHAPIRO: Why is Earth's so much stronger then?
FRANK: Well, it's all about what's happening in the Earth's core. So you know, thousands of miles below our feet, the core of the Earth is actually - it's so hot that it's made of iron and nickel, and it's molten. It's flowing. And you know, we all know that metal makes good conductors, right? Well, here we've got flowing metal, and that's essentially a current, right? When you run a current through a wire, what you're actually get - is that generates magnetic field.
So in the center of the Earth, since the Earth is spinning, all that molten, liquid iron is splashing around and spinning around. That creates huge currents, and those huge currents create the huge magnetic field that we have.
SHAPIRO: Well, thank you, Earth's magnetic field.
FRANK: (Laughter) I agree. Let's send it a card.
SHAPIRO: That's University of Rochester professor and NPR science blogger Adam Frank. And if you have a question about physics, astronomy, science in general, just send us a note, and we will put Adam's Ph.D. to good use. The show is on Twitter @npratc. You can find us on Facebook as well. Thanks, Adam.
FRANK: Thank you. Transcript provided by NPR, Copyright NPR.