Talk:Magnetic levitation

Diamagnetically-Stabilized Levitation
A permagnet can be stably suspended at room temperature without either servo control or superconductors by various configurations of strong permanent magnets and strong diamagnets. When using superconducting magnets, the levitation of a permanent magnet can even be stabilized by the small diamagnetism of water in human fingers. This bit looks nonsense, especially as it seems to either contradict other stuff in the article, or be totally redundant depending on how I read it. I'm moving it here in case anyone wants to comment on it...

Whitepaw 18:40, 8 June 2006 (UTC)


 * It's a real effect, though poorly written. reference that says almost the exact same thing — Omegatron 23:21, 8 June 2006 (UTC)

The point being made is that a magnetic force can overpower a force of gravity within the volume of interacting space between two objects. Which argues for the existence of some kind of material within that spacial volume that is capable of creating that physical force.WFPM (talk) 20:38, 22 October 2012 (UTC)

Levitation of aluminium
Many years ago on british children's tv I saw a large and heavy telephone book being levitated. It was then explained that this was due to an aluminium plate hidden within it.


 * If you could remember the name of the show and other information, that might be notable enough to include in the article. — Omegatron 22:31, 10 June 2006 (UTC)

Added reference to NeFb ring magnet array / Fermilab — Preceding unsigned comment added by 208.54.95.1 (talk • contribs) 01:50, 9 October 2006 (UTC)

Edit as 22.10.2006
Hi, I re-inserted the section on electrodynamic suspension, not sure why it was removed as it is an important principle. PLease give reason why it should not be in. — Preceding unsigned comment added by 144.82.208.69 (talk • contribs) 22:57, 22 October 2006 (UTC)

equation
I don't understand the equation at all. What "minimum criteria" is this measuring exactly? Minimum mass? Minimum volume? Minimum diamagnetic field? What exactly is measured in T-squared over m? The examples of water and graphite are no help since you do not explain how you reached the figures involved. Nor do I understand what >> means. Widsith 15:21, 4 September 2007 (UTC)

Inductrack
There's a lot of advertising for Inductrack here, should this be mentioned by name in the main article or just linked to or what? —Preceding unsigned comment added by 129.215.188.108 (talk) 15:15, 5 September 2007 (UTC)


 * epic lulz for the current graffiti http://ebaumsworld.com/ —Preceding unsigned comment added by 86.147.24.158 (talk) 14:25, 25 September 2007 (UTC)

Possible to create an aircraft supported by mag lev alone?
Is it possible? 64.236.121.129 15:58, 3 October 2007 (UTC)

No, A Maglev Vehicle would need to be held steady by an upright force from an electromagnet, Meaning, the aircraft would be stationary on the ground (Or moving, but thats a train) 89.242.174.104 (talk) 19:37, 31 March 2008 (UTC)

Popular Myth
Earnshaw's theorem says about point objects. And not about sized objects. See example. Do you think it is unstable? --Termar (talk) 18:00, 25 September 2008 (UTC)

In fact Earnshaw's theorem applies to non point sized objects, so that configuration is unstable.- (User) Wolfkeeper (Talk) 18:05, 25 September 2008 (UTC)

This is myth. Do you think system of two equally charged coupled torahs is unstable? --Termar (talk) 18:10, 25 September 2008 (UTC)


 * 'Fraid it's not a myth. And with two equally charged coupled torah's the pages either stick together or the two books fall apart; they don't levitate. That would be a miracle truly worthy of a holy book.- (User) Wolfkeeper (Talk) 18:34, 25 September 2008 (UTC)


 * Toruses...

--Termar (talk) 18:48, 25 September 2008 (UTC)


 * 'Fraid not. Gauss's Theorem (actually the force inside a closed surface is usually zero- or if it's not due to an uneven charged distribution then it's unstable due to Earnshaw's theorem.) The reason is that the total force on the particles that make up the objects can be added together, so you can make an equivalent potential that has the same overall effect but acts at a point with all the mass acting there. Then from Earnshaw's theorem, it's inevitably unstable to any combination of inverse square law based forces.- (User) Wolfkeeper (Talk) 19:03, 25 September 2008 (UTC)


 * 1) The smaller torus is not in closed surface of the bigger torus, so Gauss's theorem is not applicable.
 * 2) You can't make an equivalent potential. You can make equivalent force field. May be. But why it will be potential? Let we see two hard-linked points in potential field of one point. Try find potential for their mass centre.Termar (talk) 07:28, 26 September 2008 (UTC)

Do not use this section as a reference
Regardless of what is decided here, using this talk page as a reference would be original research, which is not allowed. Please instead concentrate on academic and peer-reviewed journals as reliable sources. -- Good Damon 18:00, 1 October 2008 (UTC)
 * Can I demand reliable sources about sized objects unstability? --Termar (talk) 18:15, 1 October 2008 (UTC)
 * Absolutely. If a statement in the article lacks a citation, you may place a tag after it, or even just remove it (making sure you fill in a reason why). But it looks like the discussion is ongoing on this, and you may want to hold off on outright deletion until consensus is reached on this talk page. -- Good Damon 18:58, 1 October 2008 (UTC)

Earnshaw's Theorem
Earnshaw's Theorem points to the fact that there can be no stable equilibrium node when all the forces involved are inverse square law forces measured from a common origin. If magnetic repulsion and gravity were both inverse square law forces measured from the same points of origin, then Earnshaw's theorem would mean that magnetic levitation is impossible. But magnetic levitation does happen, so it is not therefore impossible. Since Earnshaw's Theorem follows from sound mathematical principles, it is hardly likely to be wrong. So we are left with no choice but to conclude that magnetic levitation occurs because either,

(1) the magnetic point of origin is different than the gravitational point of origin,

or

(2) because the magnetic force does not obey an inverse square law, contrary to what is commonly believed. If we accept Maxwell's theory that magnetic repulsion is a product of centrifugal force, then we will have reason to believe that magnetic force may obey an inverse cube law, hence allowing for a stable equilibrium node in conjunction with gravity, just as in the case of planetary orbits.

or

(3) both.

It would seem that this storm in a teacup about magnetic levitation defying Earnshaw's Theorem is based on a faulty conception of the electromagnetic forces. David Tombe (talk) 23:30, 24 May 2009 (UTC)


 * If we add not inverse square law forces, the theorem will not applicable. For example, we link two magnets by a solid rod. Termar (talk) 13:21, 22 October 2010 (UTC)

Astronauts
It would be interesting if relevant material could be found about the potential use of magnetic levitation in the training of astronauts. Currently, astronauts have to use special accelerating machines to practice their levitation abilities, but it is possible that in the future, the levitation could be achieved by using electromagnetic energy instead of simulating gravity effects at high speeds. ADM (talk) 01:34, 20 July 2009 (UTC)

Magnetic levitation system mass
If we prepare and operate and operate a magnetic levitation system within a device such as a gravitational force measuring scale and then try to list the mass of the components of the levitation system, are we able to assign a value of zero to the mass of the spacial volume within which the supportive levitating is created? In other words are we creating a force within a volume of space where there is no matter? Is that a reasonable concept?WFPM (talk) 17:14, 13 October 2012 (UTC) Carried further, why are we not applying more of our most basic technologies to moving one gallon of water ten miles away? Granted, horizontal magnetics are not the same as vertical lifting forces when applied to an immersed boundary. Laminar horizontal distribution of water by hydromagnetic means is possible. Application of propulsion of a modern submarine would seem a good place to start. Scale up the water debate.

Statically Stable Bowl-shaped Magnets
I thought (and was taught) that you cannot get magnetic levitation with any geometry of magnets alone. However, I saw this somewhat odd youtube video that shows just that... a bowl-shaped magnet casually tossed into a larger bowl, floating in what is obviously a stable equilibrium... my first thought was: "what I just saw is impossible", but the rather dull nature of the video & editing leads me to believe it is not elaborate CG... around the same time in the video they show other stable configurations, but they are usually supported by a table or sheet of plexiglass too. Crazy, no? I know the levitron also has a much-needed hole in the middle, so that much seems to help it's believability. Is there any obvious explanation I am missing? or does Earnshaw's theorem now *only* apply to points & spheres? :-/ --Osndok (talk) 04:38, 1 April 2014 (UTC)

I've uploaded an illustration of what I think is going on... maybe it will provoke some ideas & discussion? --Osndok (talk) 16:42, 19 October 2015 (UTC)



Hi, in the video you mentioned the inner bowl floats but also touches sides of the outer bowl (mechanical constraint) so you can call it pseudo-levitation ;) Tpawicki (talk) 09:22, 2 November 2018 (UTC)

Force and Stability
The article as written was hard to follow because it moved directly into discussing stability without first discussing upward force. Obviously, sine qua non for levitation is that you must have an upward force greater than gravity! Without this, discussing how to make levitation stable is a completely moot point.

I rewrote the article to move all the discussion of upward force before the discussion of stability and Earnshaw's theorem. This now make it quite clear that the article hasn't actually mentioned where the upward force comes from in any kind of magnetic levitation other for diamagnetic levitation.

The simplest levitation is to have a disk magnets positioned above another disk magnet, with like poles facing each other. This is obviously unstable (the magnets strongly want to flip over!) It's probably worth discussing this simple case (where it's easy to see why it flips over) before going into the more complicated ones. Geoffrey.landis (talk) 15:24, 16 April 2014 (UTC)


 * I'm not convinced by your changes, the old article did mention that lift occurs due to magnetic pressure and seemed to give the superconducting case as an example.


 * The old article had an entire top level section on Lift, if you look at the table of contents in the old article, it's clear that that's the case; and that it's separate to stability, which was another section. It was quite a small section though, and it could be usefully expanded.


 * The "entire top level section" you refer to consisted of a single sentence on lift: "Magnetic materials and systems are able to attract or press each other apart or together with a force dependent on the magnetic field and the area of the magnets, and a magnetic pressure can then be defined." (after this, it jumps to a calculation of superconducting levitation, without actually mentioning that superconductors are only one form of levitation).  You actually think that this comprises a clear explanation?


 * In any case, however, I kept that sentence. It is still the first sentence under lift.  I just moved the other discussions of lift, previously buried deep in the article, to follow it.


 * With your changes you have moved all of the diamagnetic levitation material to the front of the article. That doesn't seem to be a good idea a lot of levitation systems just use permanent magnets (but some don't for example the japanese train doesn't have any permanent magnets, and doesn't use diamagnetism at all so far as I know.)GliderMaven (talk) 16:55, 16 April 2014 (UTC)


 * Good idea-- there is no discussion of how these work (there never was)-- why don't you write one? Geoffrey.landis (talk) 17:40, 16 April 2014 (UTC)


 * The article remains a poorly-written one, with a superficial discussion of lift that quickly jumps to an extensive discussion of stability, and then randomly oscillates between discussing stability but not lift in some places ("mechanical constraint, for example, is the first example listed under "methods." Mechanical constraint is not a method of magnetic levitation.  It is a method to stabilize an object that is levitated some other way), and lift but not stability in others (the section "induced currents" does not discuss stability). Geoffrey.landis (talk) 15:05, 27 October 2014 (UTC)

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Where's the magnetic levitation?
I've removed the image on the left from the article because it doesn't illustrate what the caption says it does. It's a photo of a sculpture which happens to be titled "Levitation", but there's nothing to indicate that any actual levitation is taking place. Having looked at the full size image I can see no evidence of magnets, nor is there any "box". What we do have is two sections separated by a diagonal mirror, quite possibly with some additional support behind it, which, when viewed from a suitable angle, gives the illusion of one floating above the other.

By the way, the viewing angle is rather unsuitable, IMO, due to the line between wall and floor passing behind the mirror. Took me a while to work out what I was looking at, even at full size... Fortunately there's another example of the artist's work (right) which gives a much better illustration of the effect he was trying to achieve. Hopefully it's clear there's no magnetic levitation going on.

Now all we need is a replacement which actually does show two magnets in a box. Shouldn't be too hard? 79.73.150.27 (talk) 00:44, 11 August 2016 (UTC)

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Mach number
Mach number for maglev trains Jithesh A T (talk) 16:51, 23 October 2018 (UTC)