Physicists circumvent centuries-old theory to cancel magnetic fields:
A team of scientists including two physicists at the University of Sussex has found a way to circumvent a 178-year old theory which means they can effectively cancel magnetic fields at a distance. They are the first to be able to do so in a way which has practical benefits.
[...] "Earnshaw's Theorem" from 1842 limits the ability to shape magnetic fields. The team were able to calculate an innovative way to circumvent this theory in order to effectively cancel other magnetic fields which can confuse readings in experiments.
In practical terms, they achieved this through creating a device comprised of a careful arrangement of electrical wires. This creates additional fields and so counteracts the effects of the unwanted magnetic field. Scientists have been struggling with this challenge for years but now the team has found a new strategy to deal with these problematic fields. While a similar effect has been achieved at much higher frequencies, this is the first time it has been achieved at low frequencies and static fields -- such as biological frequencies -- which will unlock a host of useful applications.
Journal Reference:
Rosa Mach-Batlle, Mark G. Bason, Nuria Del-Valle, et al. Tailoring Magnetic Fields in Inaccessible Regions, Physical Review Letters (DOI: 10.1103/PhysRevLett.125.177204)
The finding has potential application in quantum technology and in medicine.
(Score: 2, Informative) by Anonymous Coward on Friday October 30 2020, @05:09PM (1 child)
The theory is fine. They are not circumventing it, but working within it. This is a application of metamaterials for magnetics. Just like for electromagnetism, you can do some funky things with negative permittivity materials where you build up this negative permittivity by using a bunch of isolated sources. It is the combination of all of these many sources that selectively add/cancel resulting in the desired shapes, but all of these sources are acting just like they should.
This isn't the only way to "circumvent" Earnshaw. Perhaps a decent number of readers have already violated Earnshaw with a clever little toy [wikipedia.org]. Here you are leveraging gyroscopic precession [ucla.edu] in the magnetic field to "violate" Earnshaw.
(Score: 4, Insightful) by ikanreed on Friday October 30 2020, @06:14PM
"Circumvent" doesn't usually mean "violate" in common English parlance.
(Score: 1) by anubi on Saturday October 31 2020, @01:01AM (2 children)
I once worked with someone who claimed these did really odd things by focusing magnetic fields.
Apparently mechanized on both stick and toroid form factor.
I never got one to do anything useful... Just another lossy inductor.
Anyone else have insight, or did I just get duped into yet another wild goose chase?
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 0) by Anonymous Coward on Saturday October 31 2020, @01:18PM (1 child)
Looks like some crackpot shit chasing free energy from what I could find.
(Score: 1) by anubi on Sunday November 01 2020, @12:10AM
My sentiments too.
There is another version out there too, wound on a ferrite rod. Wound such that the layers of the windings overlay at right angles.
Been trying to find the name of the thing.
It's pretty to look at, but I never succeeded at making it do anything useful either. It just looked intriguing.
As if these were designed to appeal to the "dress to impress" crowd.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]