On: Recover HD Using a Magnet

[FabHK]

Isn't it inverse square?

[mlyle → FabHK]

No. Magnetic fields fall off as 1/d when d is small compared to the size of the magnet, progressing to 1/d^3 when d is large compared to the magnet. (E.g. weird edge case-- it's inversely proportional to distance from an infinitely long wire).

Electromagnetic radiation from point sources falls off as 1/d^2.

[FabHK → mlyle]

Thanks a lot, both of you, learned something!

[egdod → FabHK]

No, it’s a dipole moment instead of a monopole like electric charge. It goes as 1/r^3 in the far field.