[macromaniac]

He doesn't provide an actual counterargument,he just says he doesn't like the data without explaining why.

His earlier comment that graphite can do the same thing is untrue afaict. Graphite can repel the magnetic field but it would slide off, this is why in diamagnetic experiments multiple magnets are used to keep it in place. In the video it doesnt seem to be sliding anywhere, so imo the video is not showing diamagnetism.

https://sciencecast.org/casts/suc384jly50n

Edit: Actually, now I'm not so sure, it does seem like it's held in place by one corner which is always pointing towards the outside of the magnet, so maybe it is just diamagnetism. If anyone has some pyrolytic carbon and wants to try it out?

Edit2: 99% of YouTube videos on diamagnetism have multiple magnets, the only one I could find that has diamagnetism on one pole magnets shows it not working:

https://youtu.be/D-tW8_SRW3g

I think it's more than just pyrolytic carbon

[whatshisface]

It is clearly resting on the magnet. I don't know the mechanics off the top of my head, but that is enough mechanical constraint for a pair of permanent magnets to levitate.

[willis936]

It isn't. Permanent magnets would be unstable. This would have to be a diamagnetic or superconducting material.

[jeepers6]

Superdiamagnetism occurs primarily in superconductors.

Reminder that flux-pinned levitation only occurs when superconductors are cooled from above to below their critical temperature while in a local magnetic field.

The researchers probably didn’t heat up their big sample above the critical temperature in air as that could have mechanically destroyed it. It was already chipped almost in two.

[mitthrowaway2]

> Reminder that flux-pinned levitation only occurs when superconductors are cooled from above to below their critical temperature while in a local magnetic field.

Casual demonstrations of levitating superconductors involve first submerging the superconducting material in a (non-magnetized) tub of LN2, and then moving it onto a magnetic track. For example, https://www.youtube.com/watch?v=X5EoUD-BIss

[jeepers6]

That’s true, surprising to hear that the YBCO SC in that video is only 30um think.

[IshKebab]

It is, depending on how big the contact patch is. But does look pretty small in this video and it doesn't really behave like a permanent magnet would.

[sockaddr]

I’m not convinced it’s levitating in the video, imagine a magnetic field strong enough to partially lift the fleck but also a patch of the fleck contacting the magnet with enough friction to keep it from sliding away.

[floxy]

>so maybe it is just diamagnetism.

Superconducting levitation is just due to the perfect diamagnetism of the superconductor, right?

https://en.wikipedia.org/wiki/Superdiamagnetism

[weberer]

>He doesn't provide an actual counterargument,he just says he doesn't like the data without explaining why.

Welcome to Reddit

[_4bjt]

One of the authors explains in this article: https://www.newscientist.com/article/2384782-room-temperatur...

> However, only one edge of the flat, coin-like material fully levitates, while the other seems to stay in contact with the magnet. Kim says this is due to the sample being imperfect, which means that only some part of it becomes superconductive and exhibits the Meissner effect.

[mhh__]

Intuition shouldn't be considered harmful.