Moses effect

In physics, the Moses effect is a phenomenon of deformation of the surface of a diamagnetic liquid by a magnetic field.[1][2] The effect was named after the biblical figure Moses, inspired by the mythological crossing of the Red Sea in the Old Testament.[2]

Direct (A) and inverse (B) Moses effects.

The rapid progress in the development of neodymium magnets, supplying magnetic fields as high as c. 1 T, allows simple and inexpensive experiments related to the Moses effect and its visualization.[3][4][5] The application of magnetic fields on the order of magnitude of 0.5-1 T results in the formation of the near-surface "well" with a depth of dozens of micrometers. In contrast, the surface of a paramagnetic liquid is raised by the magnetic field. This effect is called as the inverse Moses effect.[1] It is usually latently suggested that the shape of the well arises from the interplay of magnetic force and gravity and the shape of the near-surface well is given by the following equation:

${\displaystyle h(r)={\frac {\chi \mathbf {B} ^{2}(r)}{2\rho g\mu _{0}}}}$

where χ and ρ are the magnetic susceptibility and density of the liquid respectively, B is the magnetic field, g is the gravity acceleration, and μ₀ is the magnetic permittivity of vacuum.[6] Actually, the shape of the near surface well depends also on the surface tension of the liquid. The Moses effect enables trapping of floating diamagnetic particles and formation of micro-patterns.[7][8] The application of a magnetic field (B≅0.5 T) on diamagnetic liquid/vapor interfaces enables the driving of floating diamagnetic bodies and soap bubbles.[9][10]