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Cut the Earth In Half

  1. Oct 25, 2009 #1
    So I had a random thought come to mind today (I've been studying magnetics in general physics lately)...

    If you cut the earth in half, evenly, from pole to pole and allowed the two hemispheres to rotate freely about the plane of the cut, but not to deviate away from eachother, what would happen?

    In my head I pictured them being two separate magnets, thereby repelling eachother, but since they're not allowed (per my assumptions) to move away from eachother, the best they could do is rotate 180 degrees about their cut plane such that half the north pole and half the south pole are touching on either "pole" that would exist after.

  2. jcsd
  3. Oct 25, 2009 #2


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    A small permanent magnet sits on the table, with N to the left and S to the right.
    Cut a magnet in half, you have two smaller magnets, each of which has N on the left and S on the right (that means S and N are adjacent). They are attracted to each other and will stick back together unless you can manage to pry them apart.
    Same thing with Earth.
  4. Oct 25, 2009 #3
    Wouldn't that be what happens if you cut the earth in half across the equator? I'm speaking in terms of cutting it "vertically" taking that to mean the axis is vertical. So cut from north pole to south.

    Would you not then have a north pole next to a north pole? Thus repelling...
  5. Oct 25, 2009 #4
    You would have to force one of the halves to rotate. It wouldn't do it by itself. The reason is that the pole would actually expand across the cut. You would still have one single magnet.
  6. Oct 26, 2009 #5

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  7. Oct 26, 2009 #6
    Re: Hi

    You'd only be able to cut down to the mantle, since the inner core is liquid, and I thought it was the inner core that caused the magnetic field- so a physical cut in any direction would not have any effect and be completely undermined by mutual gravitational attraction, since a planet split into two separated hemispheres has a significantly higher gravitational potential energy than a complete sphere.
  8. Oct 26, 2009 #7


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    it would be ugly. the molten guts would spew out with untold, and likely bad effects on life on the surface.
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