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[Bob-C]

Hi Tylet et al., Larry the flying frog thanks you for stopping by and invites you to see him in his latest movie entitled Larry the flying frog

Note, all the magnetic levitation movies in this post are courtesy of the Nijmegen High Field Magnet Laboratory (HFML) of the Radboud University of Nijmegen, NL.

Larry says it's hard to eat lunch while being levitated but the pay is good and he is treated well.

How is Larry the flying frog able to levitate?

The cells in Larry's body contain atoms that are diamagnetic, i.e., when they are subjected to an external magnetic field, like the magnetic field that surrounded Larry, which was produced by a Bitter solenoid (a water-cooled electrified coil of wire that produces a magnetic field which in the levitating frog experiment was 10 Tesla, equivalent to 200,000 times the Earth's magnetic field), the atoms align themselves together with the magnetic fields surrounding their electrons to generate a combined magnetic field that is anti-parallel, and therefore in opposition to, the external magnetizing field.

When the external magnetic field strength is sufficiently large it will cause the combined anti-parallel magnetic field within the frog's body to be expelled from the frog's body which will then exert a vertical upward repulsive force against the external magnetic field that was applied to the frog.

When this vertical upward magnetic force, i.e., the upward magnetic force vector of the expelled anti-parallel magnetic field, increases in magnitude due to a great enough applied external magnetic field, it overcomes the magnitude of the downward gravitational force Fg (also a vector quantity with magnitude but with a downward direction) acting on Larry the frog which results in the levitation of the frog.

Thus the net sum of the upward and downward force vectors (the resultant force vector) acts in the upward direction opposite to the pull of the applied gravitational force.

Note that an anti-gravitational field countering the Earth's downward gravitional field has not been created in the above described situation. The frog levitated simply as a result of the combination of the upward magnetic force vector and the downward gravitational force vector which resulted in an upward force vector that acted on and lifted up the frog.

As long as the electrical current remained connected to the solenoid in the flying frog movie the frog remained levitated due to the maintenance of the expelled anti-parallel upward directed magnetic field from within the frog.

The Meissner effect makes it possible for researchers and experimenters to levitate rare-earth magnets above a superconducting disk.

Superconductivity is the "falling off of the magnetic flux within a supeconducting metal when it is cooled to a temperature below the critical temperature in a magnetic field."

Walther Meissner observed in 1933 that "the Earth's magnetic field was expelled from the interior of tin crystals below 3.72 K [Kelvin], indicating that as superconductivity appeared the material became perfectly diamagnetic" from the Concise Science Dictionary, Oxford University Press (1996).


Note that before the tin crystals reached 3.72 K or 3.72o above absolute zero (absolute zero is the point where the kinetic energy of all atoms is at the lowest possible level) the tin crystals were not diamagnetic but paramagnetic.

Tin and other metals including copper, nickel, cobalt, samarium, iron, and aluminum, are paramagnetic at room temperatures. This means that their atoms have "net orbital or spin magnetic moments that are capable of being aligned in the direction of the applied [magnetic] field."

When an external magnetic field is applied to these atoms they align their magnetic fields in parallel with the external magnetic field rather than anti-parallel to it. In addition the combined magnetic field of these atoms is not expelled at room temperatures.

However, at superconductng temperatures just a few degrees above absolute zero, the normally paramagnetic substances become diamagnetic and their combined magnetic field is expelled as an anti-parallel magnetic field to the external magnetizing field.

Thus at superconducting temperatures the metallic disk that was suspended in a nitrogen coolant bath becomes diamagnetic with a vertically upward repulsive force countering the downward force of gravity similar to the situation of Larry the levitating frog whose atoms were always diamagnetic (with the exception of any metallic atoms within its body).

Note paramagnetism occurs in all atoms or molecules with unpaired or singlet electrons.

For further information about paramagnetism and diamagnetism and the difference between paramagnetic and diamagnetic materials you can read the Wikipedia article on paramagnetism here.

Larry the frog required a high magnetic flux external magnetic field to be applied to his body by the surrounding solenoid to cause the magnetic field within his body to be expelled as an anti-parallel magnetic field unlike the superconducting metallic disk that only had to be cooled down to a superconducting temperature level to turn it into a diamagnetic substance without the need of an external magnetic field.

Note that the primarily diamagnetic atoms in the frogs are not as susceptible to external magnetic fields as are paramagnetic atoms. Thus a very high magnetic strength (known as magnetic flux) field had to be applied to the frog to expell its internal magnetic field.

For additional interesting information about levitating a sumo wrestler and how superconducting levitation works read this article from HFML entitled The Real Levitation

See the the following HFML page for further information and levitation movies courtesy of HFML. Go to the right side of the page and click on the images to select movies or images of levitating objects.

Cheers, :)

Bob-C