3 ms·
The actual picture of (poor) levitation in the paper you linked is pretty compelling. This isn’t a complex, noisy measurement showing something that’s related t
by amluto 3y ago
The actual picture of (poor) levitation in the paper you linked is pretty compelling. This isn’t a complex, noisy measurement showing something that’s related to superconductivity — this is a magnet and a supposed superconductor repelling each other.
As far as I know, that’s possible with permanent magnets (and it would be weird, but not impossible, if the group instead synthesized a novel ferromagnet and didn’t notice), electrets (seems pretty unlikely here), very extreme amounts of static charge (again, seems unlikely), and actual superconductivity (would be awesome).
Random bits of cooked oxides, ceramics, and such don’t float on a magnet.
- scarmig 3y agoTheir other data doesn't line up with ferromagnetism, though. It's either the real thing or a big fraud. Guess we'll find out soon enough. ETA: the video referenced is apparently available at https://www.youtube.com/watch?v=EtVjGWpbE7k https://www.youtube.com/watch?v=EtVjGWpbE7k . Interestingly, posted on Feb 26, 2023.
- marcosdumay 3y agoYeah, that thing does really want to stay in a constant level on the magnetic field. That would dispel every other explanation on the GP, as it's not simply being repelled or attracted.
- Baeocystin 3y agoI found that video very compelling. If it was eddy current, the float standoff distance would have decayed. It sure looked to me like there was no decay at all, and wow! if true.
- oefnak 3y agoWhat is float standoff distance?
- Baeocystin 3y agoEddy currents can be induced in non-superconducting materials that make it look like levitation, but the catch is that there has to be relative motion between the magnet and the object 'levitating' to generate the currents in the first place. I've linked to a relevant example in a Veritasium video here: https://youtu.be/g0amdIcZt5I?t=543 https://youtu.be/g0amdIcZt5I?t=543 But in this sample video, the standoff distance doesn't appear to be slowly dropping at all, which would rule out eddy currents as a source of the behavior. If you continue watching the linked video to 13:27, he talks about how and why superconductors levitate.
- deleted 3y ago[deleted]
- mildchalupa 3y agoElectromagnetic solenoid designer here... Copper and a magnet can certainly interact. Drop a magnet through a copper pipe and the eddy currents will induce a field that's opposed to the magnet causing a damping effect. Maybe something like this is going on where movement of the magnetic field is inducing an opposed magnetic field in the copper, and thus interacting. Anyhow it will be interesting. if It can generate a field of 1.5-2 Tesla you could have more efficient solenoids and probably motors.
- colechristensen 3y ago>As far as I know, that’s possible with permanent magnets (and it would be weird, but not impossible, if the group instead synthesized a novel ferromagnet and didn’t notice) As far as I know a stable arrangement of permanent magnets levitating is impossible without a baring surface to keep them aligned. (i.e. free floating levitation is not possible without active control)
- floxy 3y agoJust so everyone is on the same page, static passive diamagnetic levitation is possible with materials like pyrolytic graphite. https://en.wikipedia.org/wiki/Diamagnetism https://en.wikipedia.org/wiki/Diamagnetism https://www.kjmagnetics.com/blog.asp?p=diamagnetic-levitation https://www.kjmagnetics.com/blog.asp?p=diamagnetic-levitatio... ...and superconductors are usually perfectly diamagnetic.
- colechristensen 3y agoEvery substance is one of * ferromagnetic - attracted to one pole of a magnet but not the other (in a given orientation), this is what everybody thinks of when they think of "magnets" * paramagnetic - attracted to both poles, i.e. stuff that sticks to magnets * diamagnetic - repelled by both poles, except in superconductors, this effect is very weak compared to the forces experienced involving ferro-ferro or fero-paramagnetic materials. There isn't another category, everything fits in to one of those buckets. Saying >Just so everyone is on the same page, static passive diamagnetic levitation is possible with materials like pyrolytic graphite. is a bit deceptive, as what people know as "magnetic" materials are ferromagnetic.
- CMScientist 3y agoYou literally missed the most common magnetic phase - antiferromagnetism
- jacquesm 3y agoThat's not quite true. There is a Halbach array with a bunch of compensation coils that will nicely center as long as it is moving, no active control or bearing required. https://www.sciencedirect.com/science/article/abs/pii/S0304885311001181 https://www.sciencedirect.com/science/article/abs/pii/S03048... And many others besides. Halbach arrays are fascinating.
- PlasmonOwl 3y agoI would say that this type of levitation where it sort of half levitates is quite common. I taught YBaCuO superconductor experiments for a few years. That Meisner effect would get full marks in my institution!
- whatshisface 3y agoBelieve it or not, the levitation effect can be found in non-superconducting materials with a high diamagnetic constant such as pyrolytic carbon. Induced magnetic fields are created by "effective currents," which can occur in zero-resistance systems that are not called superconductors (because they can't conduct across a significant distance, only around a tiny loop) like molecular or atomic orbitals. https://en.wikipedia.org/wiki/Pyrolytic_carbon https://en.wikipedia.org/wiki/Pyrolytic_carbon
- howmayiannoyyou 3y agoDiamagnetism was my first reaction when I saw lead, and the addition of copper makes me think eddy current reactivity.
- rozab 3y ago...and this is Eddy's sofa, is it?