Isn't magnetism governed by the inverse square law?

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Magnetic dipole forces fall off with $r^{-2}$ when close to the magnet and transition to $r^{-3}$ at greater distances.

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uKER
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uKER

Updated on June 14, 2022

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  • uKER
    uKER over 1 year

    Why does magnetism appear to decay much faster than gravity with distance?

    A clear indication of this is the fact that a magnet that in short distance able to overcome gravity and pick up some object, is quickly overpowered by gravity as any short distance is put between the magnet and said object.

    Gravity, as we all know, is governed by the inverse square law. Shouldn't they both decay at the same rate?

    • Barbaud Julien
      Barbaud Julien about 5 years
      Why should they be the same rate ? You can find in any book of electromagnetism (or wikipedia), the analytical solution to the magnetic dipole problem. The magnetic field decreases as 1/r^3. why should it be 1/r^2 ?
    • BioPhysicist
      BioPhysicist about 5 years
      And even then, just because two things drop off like $1/r^2$ does not mean they have the same strength. As an example, I will hear much more sound intensity standing two meters away from a helicopter than standing two meters away from a person talking to me.
    • uKER
      uKER about 5 years
      @AaronStevens The problem would arise if walking two steps away from both the helicopter and the person, the person suddenly became louder than the chopper.
    • uKER
      uKER about 5 years
      @BarbaudJulien I figured it would, basically because that's the rate at which every energy in the universe falls off. I'm guessing it being an exception to this is probably due to the fact that magnetism isn't uniformly radiated in every direction, but a structured phenomenon.
    • BioPhysicist
      BioPhysicist about 5 years
      Also keep in mind that on the surface of the earth the gravitational force is practically constant.
    • John Rennie
      John Rennie about 5 years
  • anna v
    anna v about 5 years
    the gravitational force is f=mg in the case described above. It is the constants in front that determine the size of the forces in neutons