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.
ETA: the video referenced is apparently available at https://www.youtube.com/watch?v=EtVjGWpbE7k . Interestingly, posted on Feb 26, 2023.
I've linked to a relevant example in a Veritasium video here: 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.
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.
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)
https://en.wikipedia.org/wiki/Diamagnetism
https://www.kjmagnetics.com/blog.asp?p=diamagnetic-levitatio...
...and superconductors are usually perfectly diamagnetic.
* 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.
https://www.sciencedirect.com/science/article/abs/pii/S03048...
And many others besides. Halbach arrays are fascinating.
Halbach arrays with compensating coils have been proposed for some interesting applications, such as low loss flywheels for electrical storage. I don't know if that ever got commercialized but I do recall that some prototypes were made by a US company. I can't find a reference to it though.
Not too much longer apparently...
Is it late April Fools joke?
It can’t be true.
So, yeah: big if true.
> Detritus blinked. There was a tinkle of falling ice. Odd things were happening in his skull. Thoughts that normally ambulated sluggishly around his brain were suddenly springing into vibrant, coruscating life. And there seemed to be more and more of them.
> 'My goodness,' he said, to no-one in particular.
> This was a sufficiently un-troll-like comment that even Cuddy, whose extremities were already going numb, stared at him.
> 'I do believe,' said Detritus, 'that I am genuinely cogitating. How very interesting!'
> 'What do you mean?'
> More ice cascaded off Detritus as he rubbed his head.
> 'Of course!' he said, holding up a giant finger. 'Superconductivity!'
> 'Wha'?'
> 'You see? Brain of impure silicon. Problem of heat dissipation. Daytime temperature too hot, processing speed slows down, weather gets hotter, brain stops completely, trolls turn to stone until nightfall, ie, colder-temperature,however,lowertemperatureenough,brain operatesfasterand—'
> [...] Detritus sat down again. Life was so simple, when you really thought about it. And he was really thinking. He was seventy-six per cent sure he was going to get at least seven degrees colder.
-- Men At Arms by Terry Pratchett
[0]https://www.greenoptimistic.com/make-superconductor-home/
Edit: Judging by Fig 4, which has a large object conspicuously labeled "magnet", that's probably what they're referring to.
This group used somewhat nastier powders, they had to cook parts of it in a vacuum, and they floated the result on a magnet instead of vice versa. And it only floated a bit. But they did it without any cooling!
You could almost make this stuff in a pizza oven.
The failure modes would mostly be the same as for the big ones: sucking in metal chairs if you're not careful.
If this proves true I'd see their use more in electronic circuits. Novel sensors etc rather than classic high power high field uses people dream about when the words "room temperature superconductivity" gets thrown about.
"Lead in solders for servers, storage and storage array systems, network infrastructure equipment for switching, signalling, transmission, and network management for telecommunications"
( https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A... )
The bar is even lower than that. For example, bullets are still made of lead, not because it's necessary, but because it's cheap, and despite the fact that it contaminates the meat of the hunted animal with lead.
The consumer market still uses it, which is probably a tiny fraction of what the military uses in training.
First, terms - brass is not used to "jacket" a bullet. Brass is used as the case material for the cartridge. Steel, and nickel plated steel are some times also used here. "Jacketing" (as in, Full Metal Jacket) refers to the material that wraps around the exterior of the projectile. As far as I'm aware, the material used here is almost always copper, or a copper alloy (cupronickel).
The US standard bullet is the M855. It's a lead core with a soft soft steel penetrator at the tip, that's jacketed with copper.
There's an advanced version of the M855, the M855A1, which is an entirely steel slug, jacketed with copper. This bullet has better terminal performance at longer ranges, and slightly better armour piercing capabilities.
The US army standard training round is the M193. It is a lead bullet jacketed with copper. Interestingly, it in many ways has better terminal performance than the M855 because this is the bullet the M16 and M4 rifles were designed around, and the M855 only exists because of NATO politics.
There are no bullets in the US inventory, to my knowledge, that use a copper core. Copper is simply far too expensive to be used at that scale, and, as you pointed out, reduces the weight of the projectile which has negative effects on terminal performance.
"Why are bullets jacketed in copper" you might be wondering here - when rifle cartridges were invented, they still used black powder, and all bullets were lead. When smokeless powder was invented, it became possible to have more explosive power per unit of volume. However, this had two negative effects - one, the lead projectile would either disintegrate, or became entirely inaccurate, at the speeds it was accelerated to. Second, the force of the bullet against the rifling of the barrel was rubbing away metal from the bullet, leaving lead deposits which fouled the gun and made it inaccurate. All steel bullets solved this problem, but increase the wear on the barrel. The solution was to coat (jacket) each bullet in a thin layer of copper, which was stiff enough to withstand the force of friction in air, while also softer than the steel barrel and reduced wear and tear on the rifles
Photos of cross sections of the M855 and M855A1:
https://twitter.com/izlomdefense/status/1202516482082639872/...
Ignoring the jacket, M855 has a lead plug behind a steel penetrator. M855A1 has a copper plug behind a steel penetrator. So, I stand by my "copper where the lead used to be". I never said there wasn't a steel penetrator.
From https://en.wikipedia.org/wiki/5.56%C3%9745mm_NATO:
>For general issue, the U.S. Army adopted the M855A1 round in 2010 to replace the M855. The primary reason was pressure to use non-lead bullets. The lead slug is replaced by a copper alloy slug . . . The U.S. Marines adopted the Mk318 in early 2010 due to delays with the M855A1. This was a temporary measure until the M855A1 was available for them, which occurred in mid-2010"
As you probably know, most combat soldiers in the US Army and Marines carry a rifle that fires 5.56×45mm NATO, so it is probably the ammo type that the US military has the most of.
Yes the M855A1 was developed and started operational testing in 2010. However, it wasn't available to anyone who wasn't forward deployed until...my memory says 2015. The M855 is still used on post because a) it's cheap, and ballistically similar to the M855A1 and b) the production lines at Lake City are still geared for them
The Marine corps didn't formally adopt the M855A1 until 2017/2018. Brass didn't like it because it broke the feed ramps on machine guns. There was a big procurement SNAFU about this.
Marine corps times article on the matter:
https://www.marinecorpstimes.com/news/your-marine-corps/2017...
I get that you're trying to be snide because you were so publicly wrong, but your tone here really just makes you sound like you're trying to sound smart about something you know nothing about. Something to consider. Frantic googling does not an expert make.
You're right about the copper core on the new model A1 - I thought it was steel entirely with thin jacket. I would argue that when, by weight, the majority of the bullet is steel, my original point still holds.
>I get that you're trying to be snide because you were so publicly wrong, but your tone here really just makes you sound like you're trying to sound smart
Right back at you. I don't think I'm motivated by trying to sound smart, but rather by curiosity about the subject. Well, OK, half by wanting to sound smart (and win arguments) and half by curiosity.
In particular, I'm still curious about whether ammunition containing lead is still routinely used by the US military--if you still want to talk about it. I realize Wikipedia can be totally wrong. So far I haven't succeed in wringing information out of Google Search that would corroborate or support your assertion. When's the last time you (or someone you know to usually tell the truth) has observed M855 being used by the US military in significant quantities?
EDIT TO ADD: I don't know if that qualifies as "quantities" and anecdotes are just that, but that's been my experience.
As I understood the standard M4 with 1:7 barrel can't shoot M193 accurately
Those are often bismuth weights.
Most people aren't licking the insides of their computer processors, fusion reactors, radio telescopes and MRIs.
For instance in EU, https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A...
Canada, https://www.canada.ca/en/health-canada/services/environmenta...
Compared to refining traditional conductors and recycling/disposing of used electronics?
> you still have to use lead-free solder
One, fumes. Two, people touch their solder and then grab a cookie.
We're premature. The results need to be proven. But the benefits of RTP superconductors is mindblowingly high enough that risks from lead contamination (far from a novel problem, I might add) can be safely ignored.
You might want to read more in the links I shared about the harmful effects of lead before "whatabouting" to other problems of electronics recycling/waste.
and yes, it's entirely possible this application would get an exemption from usual restrictions on lead. For example in the EU directive, one of the exemptions is:
> Lead in solders for servers, storage and storage array systems, network infrastructure equipment for switching, signalling, transmission, and network management for telecommunications
But people don't, particularly students, and sometimes they also let their irons run too hot at which point fumes become an issue. Also, there is an easy alternative, so why not.
If the choice is lead superconductor or not, nobody is going to pause on a use case because there is lead. If they do, and if this is real, please let me know--I'd love to have them as competition.
> might want to read more in the links I shared about the harmful effects of lead before "whatabouting" to other problems of electronics recycling/waste
The point is, whether a RTP superconductor does or doesn't contain lead is irrelevant to its adoption. The advantages are too large. What current directives say are, similarly, irrelevant.
IMO, the most dangerous thing about lead solder is cleaning the iron. Both the common methods (damp sponge and brass wool) create many tiny little balls of solder that are hard to see and bounce about all over the place. Because of the high density of lead they're less affected by air resistance than you might expect, and they roll easily, so they can move surprising distances. They can easily end up caught in clothing, and from there fall into food. This will result in much higher lead ingestion than just touching solder then touching food.
I personally always use lead-free solder. If you have a good temperature controlled soldering iron it's nearly as easy to use as leaded solder.
The last time I checked, low-temperature bismuth-tin alloy is only available as solder paste, unfortunately not available as flux-core solder wires (they're not really a good choice for connectors to begin with as the alloy is brittle, but I only need it to survive before the next prototype...)
It's trivial to experimentally demonstrate that solder fume contains almost no lead, the quantity is negligible. Claiming the contrary is the electronics equivalent of saying HTML is a programming language. Please don't do that again. The fume is indeed toxic, but it's due to the VOCs from the flux core, not the lead in the alloy.
A more solid (no pun intended) argument can be the hazards of debris. Furthermore, in my opinion, a newer and more serious problem of leaded solder today, in a workshop setting, is its use in solder paste. Solder paste and a reflow oven are required for prototyping any circuit boards with surface-mount components (SMT) - basically any modern circuit board today. Solder paste is a tube of toothpaste-like chemical mixture that contains tiny, micrometer-sized metal particles, mixed with sticky flux. If they're used without care, a solder paste spill is a sure way to contaminate the floor or work surface of your workspace. The sticky paste is also hard to wash away from skin.
Unfortunately, reflow soldering of surface-mount components can be really challenging, even more so when doing it by hand. Thus, classic lead-tin alloy is often used to reduce difficulties of assembly during workshop prototyping due to its technically superior properties. Switching to lead-free is only possible when you have a tightly-controlled and consistent work flow.
If you want lead-free, for small-scale prototyping and rework, a non-toxic bismuth-tin alloy is sometimes a good alternative to standard SAC305 lead-free solder thanks to its low melting temperature, which is one main reason that makes most lead-free alloys difficult to use (it even has considerable popularity in mass production of LED devices, as they are heat-sensitive). But its surface tension is slightly different, weakening the self-alignment effect of components during reflow soldering, increasing the chance of defective joints - a concern in prototyping. Its brittle nature also increases failure rates in the field, among other caveats.
Lead is really a gift from the devil.
This is incorrect. You can easily do small scale work with almost all SMT components without solder paste. Solder paste is required for automated assembly processes. But almost anything done by hand can also be done with conventional solder.
Source: I worked as an electronics designer for a few years, and assembled prototypes and small production batches by hand with SMT parts (0603's, TTSOPS, etc) every day.
The one exception is BGA devices, because the solder pads are underneath the device. But doing those by hand requires precise alignment that is difficult enough that few people do it. Also, for smaller BGA devices with fewer pins, skilled operators can still solder them in place with a heat gun by covering the pads with solder and flux and just melting them into place.
I disagree. I don't consider 0603 passives and TSSOP packages "modern" anymore. Of course these components can be hand soldered with ease (possibly at top quality with the aid of a microscope). Unfortunately, even simpler ICs like DC-DC controllers are gradually abandoning TSSOP and QFP in favor of DFN, QFN, and LFCSP in recent years. These packages are all leadless, and frequently with thermal pads at the bottom. An older term for leadless packages is BTC - Bottom Termination Components [1]
After multiple failed QFN soldering attempts, I switched to ordering stencil, solder paste, and a hot plate. It worked perfectly on my first attempt, so I never looked back.
Unless you have top 10% soldering skills, which I don't (experienced smartphone repair technicians seems to have mastered the art of QFN), I found solder paste is required for maintaining your sanity for leadless packages. Furthermore, without reflow soldering, prototype assembly can be very time-consuming and takes hours, especially when you need 3 or more prototypes.
Occasionally, leadless packages also have optional difficulties turned on, completely eliminating the possibility of hand soldering, such as multiple pads for different nets (to minimize parasitic inductance), or having two layers of contacts, one row on the exterior and on row on the interior.
> You can easily do small scale work with almost all SMT components without solder paste. [...] The one exception is BGA devices
And DFN, and QFN, and LFCSP, and...
Thanks to industrial and automotive users, some ICs still have QFP versions that are friendly for hand operation due to their vibration resistance, but you sometimes have to pay a premium.
Finally, even plain-old QFP chips have bottom thermal pad these days (in that case, you can manually apply a blob of solder on the PCB and reflow again with a hot air gun, but manually apply a drop of paste is easier to work with).
[1] But these days it would make people think it's some kind of a Bitcoin mining ASIC. BTW, the last time I've checked, these ASICs are indeed QFN, so one can say they're BTC BTC chips...
Not being in sciences I can’t tell if this sentence is legit or you just got a good joke in there
As for how to avoid lead poisoning, coat the lead with a thin layer of some substance, perhaps a plastic or rubber that doesn’t affect its magnetic capabilities.
Or perhaps they can galvanize it with safer metal, leaving a really small part exposed.
It'd likely be exempt though.
I can't tell if there is a catch anywhere, this seems pretty legitimate. Also, unlike some previous claims that required sophisticated setup to reproduce, this seems dead simple. I think we will hear from other researchers very soon.
1. Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and atmospheric pressure and mechanism: https://arxiv.org/pdf/2307.12037.pdf
2. Google Scholar: https://scholar.google.com/citations?user=_P8mux4AAAAJ&hl=en
3. Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging: https://scholar.google.com/citations?view_op=view_citation&h...