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Ferromagnetic half levitation of LK-99-like synthetic samples

arxiv.org

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Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#281

Post by postalrat »

versteegen wrote: post #10
m3kw9 wrote: post #8

Has anyone even seen a ferromagnet stand up like that in a magnetic field?

Yes. https://nitter.net/VanGennepD/status/1688052003216261120 And this new paper finally rigorously explains away all the half-levitation videos. They can no longer be considered any evidence of SC at all.

In the original video he flipped it 360 degrees off the center of the magnet yet it kept the angle it was pointed at. Wouldn't a ferromagnet want to stay orientated with the field of the magnet and flip the other direction when rotated?

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#282

Post by lessaligned »

ldjkfkdsjnv wrote: post #263
lessaligned wrote: post #257

Earlier quoted context omitted.

...nothing happened to the markets ~2017 when the transformer architecture (behind the current AI boom) happened. Nor in 2020 when it was pretty obvious shit scales and generalizes well. ONLY when it got built into an actual product (ChatGPT) did the needle start to move. Same with this, until someone figures out how to make WIRES from LK-99-like-stuff that can be made into useful MAGNETS, it will stay flat. Markets…

Transformers in 2017 basically were just better at computing similarities between blocks of text. OpenAI really did take them and turn them into something new.

"room-temp semiconductors in 2023 were just small blocks of stuff levitating atop magnets without needing to be cooled. XYZ really did manage to produce them into useful shapes that still remain superconductive when you push more than 0.00001 amps through them"

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#283

Post by 1970-01-01 »

spiderfarmer wrote: post #156
chmod600 wrote: post #139

Earlier quoted context omitted.

I think you are missing the point: a typical ohmmeter would have metal probes, so with a superconductor you would just be measuring the resistance of those probes. Any attempt to overcome that problem probably introduces a lot of chances for error or noise, or require some huge sample of the superconductor.

Zero resistance would be hard to proof this way, but why can't you compare measurements of LK99 with known conductors?

I have the same thoughts. I think it's because they are not EEs and want to play with the material. A sensing resistor is trivial.

https://www.digikey.com/en/articles/fundamentals-of-current-...

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#284

Post by dcow »

martindbp wrote: post #271
OJFord wrote: post #246

Earlier quoted context omitted.

That's not what GP means - even if you assume they're independent variables, 2x 10% probabilities combine to a 1% ('10% of 10%', they multiply, not add) probability of the total outcome, not 20%.

Huh? I think he's saying OR not AND. Why would two separate pieces of evidence make the whole less probable, that makes no sense, whether you spell out the whole thing more formally or not.

So if I find 10 people that claim, each with a 10% likelihood of being true, that the dark side of the moon has a scar that looks like Pikachu, then it’s 100% true?

That doesn’t make sense either. Seems like someone is falling prey to an intuitive fallacy of probability.

The weird model is just wrong in the first place. The commenter we’re discussing conflates the probability of two people saying something with the probability that what they say is true. So yes, you have to model the situation correctly in the first place.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#285

Post by [deleted] »

ironborn123 wrote: post #259
layer8 wrote: post #231

Earlier quoted context omitted.

The exact numbers don’t matter, but your post indicates that you seem to have the wrong mental model of how to adjust your credences. The probability of each factor decreases the overall probability, not increases.

Alright lets do some calculations. Feel free to dissect the assumptions. K event = Kim says Material L is RTSC D event = DFT says L is RTSC S event = L is actually RTSC we have assumed P(S/K) and P(S/D) are each 0.1, though we could have chosen other numbers for them as well. We want to estimate P = P(S/(K and D)) P = P((K and D)/S) P(S)/P(K and D) Assuming Kim and DFT are in the business of making positive predictio…

[deleted]

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#286

Post by throwanem »

falcor84 wrote: post #277
throwanem wrote: post #260

Earlier quoted context omitted.

It's not that it's strange, it's that it is transparently silly to claim to precisely quantify in the absence of anything resembling sufficient information for the problem to be treated probabilistically.

How about this? I keep a running probability (e.g. a 32bit float) for the successful outcome of each future event I have absolutely no idea about. At first I make it 50%, but I gradually adjust with each result, such that I aim to minimize my bias. It might sound silly, but at the minimum it would encode some information about the kind of events I'm typically asked to predict. And I do expect it could end up somethin…

"Not even wrong." An event about whose outcome you by definition have no information ("I have absolutely no idea") is an event to which you cannot assign any probability, including by assuming it's a coin flip and then treating the assumption as axiomatic. It encodes no information whatsoever because there is none to encode, and it biases all future results because you're averaging over a range that includes "data" you made up.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#287

Post by postalrat »

kewp wrote: post #110

Someone on YouTube mentioned that LK99 is ceramic ie not metal which nullifies many of its potential uses even if it does turn out to be superconducting

Do you have any idea how many crazy things are said by "Someone on YouTube"?

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#288

Post by postalrat »

vbezhenar wrote: post #79
versteegen wrote: post #10

Earlier quoted context omitted.

Yes. https://nitter.net/VanGennepD/status/1688052003216261120 And this new paper finally rigorously explains away all the half-levitation videos. They can no longer be considered any evidence of SC at all.

The only evidence of superconductivity is zero resistance. When you have a coil, pump it with current and let it rest for few years. If the current is still the same, it's superconductor. Rest are just hints.

Oh look, I just found your superconductor! https://www.youtube.com/watch?v=wWpnsMdTrXg

5 years and still has current

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#289

Post by dcow »

protastus wrote: post #26
VHRanger wrote: post #4

After reading the r/physics thread on LK-99 [1] I've cooled significantly on the matter. Basically: people who work in SC think the initial science seems very sloppy and the replication attempts don't come close to what you need to demonstrate a RT SC [1] https://www.reddit.com/r/Physics/comments/15i3h9d/lk99_megat...

The SNR of this saga is very low. A speck of something floating under a magnetic field on a blurry video is not proof of room temperature superconductivity. We've seen memes, jokes, shitposting, bravado, Soviet fan fiction, play-by-play updates from non-SMEs cooking stuff under improvised conditions. No actual resistance measurement of LK-99 with a 4 point probe. If this is real, then discoverers found this in 1999,…

Man I got so many down votes last week for pointing out that like 6 attempts have failed to replicate this miracle thing that a fraudulent paper describes that’s supposedly existed for 24 years now. My point was simply that regardless of whether some combination of the elements described actually exists with roughly the properties described, we don’t know how to make it and neither do the people who published the paper. It should be more clear than ever, now, that there are significant gaps in our understanding of whatever LK-99 is.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#290

Post by marcosdumay »

p-e-w wrote: post #85

So if good old ferromagnetism/diamagnetism is sufficient to explain the half-levitation shown in the video: How can I build my own half-levitating objects from standard materials? I've seen the science toys using pyrolytic carbon, but they are nowhere close to the effect from the video. Levitation height with pyrolytic carbon is like 1/20th of what the video demonstrates. The disc in the video looks like it's just ab…

Go through iron milling residue (that kind that is dust-like at afar, but consist of large flakes) and select some thin and long piece. Put it over a glass, and move a magnet under it. You will see it position itself on a vertical or any angle you want.

But notice that the videos circling the internet show a different behavior. Those are not homogeneous materials, and it's not easy at all to tell what they are actually doing. (But ferromagnetism on LK-99 is surprising by itself.)

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