4 ms·
Naive question, and I hope someone more knowledgeable than me can enlighten me here; Why are we even testing for superconductivity with levitation, instead of
by rishav_sharan 3y ago
Naive question, and I hope someone more knowledgeable than me can enlighten me here;
Why are we even testing for superconductivity with levitation, instead of just checking for current loss/heat loss while conducting?
- adambb 3y agoThe samples are super small and not homogeneous, so its tough to get any kind of accurate reading with probes, is my understanding.
- CrimsonRain 3y agoGenerated samples are too small and powder-like to test for that without a lot of difficulties. Note: I'm not a physicist. Just my understanding from reading.
- clmay 3y agoThis question has been asked with near identical or very similar wording in almost every LK-99 submission I've seen over the last week or so... Is there something botnet-y happening? I find it hard to believe anyone reading similar threads could have missed the numerous answers to this and similarly-formed questions that have been offered lately.
- tkzed49 3y agoIt could be the sheer volume of discussion. I've seen a lot of these posts and this is the first time I've read this question.
- clmay 3y agoMaybe it's because I have been obsessively ensuring that I read every comment on every top thread... Some kind of selection bias could be at play...
- Firmwarrior 3y agoThe top comment on every thread about every new thing on HackerNews is a half-assed debunking of it
- yieldcrv 3y agoI’ve been half assedly following this, not understanding a single word in the papers that keep coming out, not understanding the musings of enthusiasts and professionals and it looks like I know just as much that its a nothing burger, with maybe some sliver of novelty we dont have a superconductor, as expected
- Ballu 3y agoExactly. Almost every thread has this query. And surprisingly its always on the top.
- computerfriend 3y agoAt least nobody has asked about the real-world technology implications in this thread yet.
- s1artibartfast 3y agonow I have to get out my bingo card and ctrl+f "hoverboard" and "maybe purity",
- tyre 3y agoIt’s a natural question when reading about this, like asking why a police officer makes a suspected drunk driver walk a line instead of measuring BAC. Not everyone reads every (or any!) paper and story.
- whimsicalism 3y agoYes, and it is getting a little annoying at this point to be frank.
- declan_roberts 3y agoNot all of us read HN every day or follow each discussion. A lot of people don’t read the comments at all.
- rishav_sharan 3y agoMaybe it is the most natural question which comes to a lay person like me when it comes to superconducting. Not everyone can be as knowledgeable, or in the loop as you are. And I assure you that I am no bot. I acquire sustenance, go into low energy states and have a lifetime warranty like all fellow meatbags.
- carlosbaraza 3y agoThat is exactly what a bot would say... you have to prove you are human by starting a company and making $1M
- clmay 3y agoWait, you got a lifetime warranty? xD
- rishav_sharan 3y agoYep. It gets void when I die
- segfaultbuserr 3y agoA magnetic levitation demo indicates a possible Meissner effect (which is refuted here by this paper), and this is so much easier than a resistance measurement, which is a delicate task and susceptible to experimental errors. So levitation is used as a quick "first check", especially when you don't have a full lab setup to do other tests, which are much more complicated (in addition to a levitation test or a resistance measurement, one can also measure its frequency-dependent magnetic susceptibility curve, temperature-dependent specific heat curve, or its Josephson effect). One cannot measure superconductivity with an ordinary ohmmeter. Electrodes, wires and the ohmmeter itself are resistive, the meter can never show zero ohms. You need to set an experiment up with a current source and a voltmeter to measure the IV curve across the material [1]. Even then, the voltmeter will never show "zero" volt because of noise, which needs to be minimized in the experiment and removed during post-processing. In this case, sample preparation is also problematic as the synthesized material is not uniform. And your measurement is also expected to be temperature-dependent to show the material's transition to a superconductor. It's more involved than seeing it floating on a magnet, to say the least. [1] It's basically the same 4-wire Kelvin sensing used by all milli-ohmmeters. But to characterize superconductivity, you need to do even better. https://en.wikipedia.org/wiki/Four-terminal_sensing https://en.wikipedia.org/wiki/Four-terminal_sensing
- haldujai 3y agoDo you have any idea on what the ballpark cost is to do these replication experiments I keep reading about? Or the more complicated experiments you mention? Asking out of curiosity as I would have assumed it's very expensive but there seem to be many groups of varying sizes doing these and quite quickly which I would have thought would be extremely wasteful but may suggest it's more economically feasible than I had thought.
- p-e-w 3y ago> One cannot measure superconductivity with an ordinary ohmmeter. But one can measure electrical resistivity, and if the material's resistivity is much lower than that of ordinary materials, that would be super interesting and valuable, regardless of whether it is a "true" superconductor or not. If this relatively cheap material had a resistivity around 1/100th that of copper, that would be an engineering breakthrough, and determining that doesn't seem to require a super complicated lab setup. Do we have an upper bound on LK-99's resistivity, and is that upper bound substantially lower than the resistivity of typical conductors?
- est 3y agoBecause the production of lk-99 yields a puddle of mess. https://twitter.com/MarkTyler81/status/1688736978437898240 https://twitter.com/MarkTyler81/status/1688736978437898240 LK-99 == alchemy RT SC.