• Question: Why does the earth have a magnetic force

    Asked by pielover2424 to Amy, Grant, Martin, Shawn, Usman on 8 Mar 2013.
    • Photo: Usman Kayani

      Usman Kayani answered on 8 Mar 2013:

      The core of earth (picture: ) is largely made up of iron, about 80%! The earths magnetic force, or field is generated by the motion of molten iron alloys in the outer core. Roughly speaking, this means since iron is a conductor of electricity (electrons in the material can move around easily) and the molten iron are always moving around. – the “flow” of electric current generates the earths magnetic field, similar to the way an electromagnet is produced.

      There many other factors to consider though that have contributed to the earths magnetic field and have kept it going strong for so long! An electromagnet no longer is a magnet when there is no electric current flowing i.e when it is turned off or when you run out of juice but eventually it is off. The earth magnetic field keeps on going and infact changing due to its motion and the motion of the core.

      The Earth’s magnetic field makes compasses function and shields us from dangerous solar radiation. It also allows many animals including birds to use the earth’s magnetic field to find their way around the world during migration period..which I find really cool!

    • Photo: Grant Kennedy

      Grant Kennedy answered on 9 Mar 2013:

      Great question, I think Usman’s nailed it pretty well.

      Check out this crazy video, which shows how an electric current can exert a force on a metal object. This works because the current creates a magnetic field, which then creates a current in the aluminium plate. Then the two magnetic fields repel each other and the plate lifts up like magic (but not magic, physics!).

      So this is an illustration of what Usman said, the electric current in the Earth’s core generates the magnetic field!
      g

    • Photo: Martin Archer

      Martin Archer answered on 10 Mar 2013:

      There’s still a lot about the mechanism that started to generate Earth’s magnetic field that we don’t understand though, for instance what started the core moving in this way? Also we know that the magnetic field has flipped direction a number of times in the past that we know about from rocks in the sea, but we still don’t know why and how to predict when it might happen again. Just are just two examples of problems scientists are trying to understand.

      Interestingly, Mars used to have a magnetic field like Earth’s but it lost it somehow (again we don’t really know why). I’m pretty glad Earth still has its magnetic shield from the solar wind though, otherwise we wouldn’t be around!

    • Photo: Shawn Domagal-Goldman

      Shawn Domagal-Goldman answered on 12 Mar 2013:

      Everyone else beat me to the punch on this one.

      I’d add this: one of the cool things about science is how we’re always finding out new things. We’ve known about the magnetic field for a LONG time. It’s one of the first things we discovered when we began flying things in space decades ago. But we’re still finding out out more about it! Just a couple weeks ago, NASA announced new details about these field lines that we missed for the last 50 years!

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