Edward Leedskalnin (Coral Castle) describes a perpetual motion holder in his writings. I've built one and pretty much know how it works (I think). It is NOT a perpetual motion device by any means, but more like a magnetic version of a capacitor. That, I think, is the best way to describe it. (I never saw this effect demonstrated in grade school or college, which sort of surprises me.) It can be seen demonstrated here:
https://www.youtube.com/watch?v=YhiAIsJCS9Y
and here:
https://www.youtube.com/watch?v=QJSDYYaF3LA
(NOT an unknown phenomena….)
The essence of the phenomena is that a toroid of iron will retain internally a magnetic field excited by a brief current spike sent through one or more loops of wire wrapped around (encircling) a portion of the toroid. Unlike a solenoid (a bar of iron) the magnetic field does not dissipate because the magnetic field is a stable circuit (a loop). And unlike a conventional toroid, Leedskalnin's PMH device is not a solid ring, but breakable. When the ring is opened, even years after charging, the magnetic field collapses and can issue a current pulse to any winding on the now-incomplete toroid.
The closest conventional use I could find of an internal, stable magnetic field is the field creation in magnetic core memory toroids. These are known to be stable for many years and are considered essentially permanent, stored (but re-writeable) memory.
My question is: How stable is this field? Would it really last forever, or at least many, many years?
It seems that it would have less leakage than a capacitor (holding an electric field), so I'm guessing it's holding capacity would be many years. I'm also assuming that nothing is "moving" but a stable configuration of magnetic domains is created by the brief electric field (which can then be removed) which maintains the (internal) magnetic field due to their alignment. Is this correct?
(NOTE: electric energy can be retrieved from the field by wrapping a coil of wire around the material and breaking the connection. The collapse of the magnetic field induces an electric current which can light a lamp or LED with a brief pulse of current.)
Best Answer
According to this video created the same person who created this video linked in the OP, the field remains after two years.
Of course, this experiment does not reveal how strong the field is after two years, but it does show that it at least remains to a substantial degree after two years.