It reminds me of PNP & NPN transistors. Could these liquid "defects" have applications too?

Ever since childhood I've wondered why the water behind a rowboat stays flat for so long. You'd think the surrounding water would flow in and make it as wavy as everything else. Then a few years ago I was on Thera and saw the same thing with the cruise ships coming in. Their flat glassy trails would last for hours. Why does it take so long for them to vanish? It is a liquid transition that is weirdly persistent. Does anyone have an answer? If not, maybe this can be someone's wobbling plate.

If I recall correctly, I think this is usually explained as a thermocline effect where as deeper water gets churned up and mixed in the wake, it is a different temperature than the surrounding water outside the wake. This water has ever-so-slightly different fluid characteristics and so it presents a bit of a barrier to the usual diffusion and mixing you might expect.

There's also the potential for a very thin layer of some type of hydrophobic substance (like an oil) to be left behind that can dramatically reduce waves in that area. There's youtube videos around for that effect.

Probably a different amount of dissolved gasses as well.

IDK but one factor is most of the water filling the gap would come from underneath (it's at higher pressure), moving up to the surface. Its momentum carries it slightly too high, so it flows outward, then down and inward again, forming a vortex on either side. The surface looks smooth and the twin vortices woukd tend to persist.

WAG: does it have anything to do with dissolved gases slightly changing the physics of the water, making it a case of the waves seeing it as a transition between materials.

Start simple. Take a bucket of legos and run your finger through it. It will do the exact same thing - but much slower. When you embark on these super complex differential equations (people barley understand) - just go backwards.

The actual article this story is about: https://www.pnas.org/content/118/12/e2018977118

(the link was there but buried at the bottom of the page)

> While the researchers were not actively looking for any particular defect in the material, the advanced imaging technique uncovered a surface defect, called a twin boundary. At either side of the twin juncture, the molecular networks abruptly transformed their handedness.

Reminds me of Q1D models that simulated glassy dynamics[0]:

"We describe numerical simulations and analyses of a quasi-one-dimensional (Q1D) model of glassy dynamics. In this model, hard rods undergo Brownian dynamics through a series of narrow channels connected by $J$ intersections. We do not allow the rods to turn at the intersections, and thus there is a single, continuous route through the system. This Q1D model displays caging behavior, collective particle rearrangements, and rapid growth of the structural relaxation time, which are also found in supercooled liquids and glasses. "

[0]: https://arxiv.org/abs/1401.0960

> At either side of the twin juncture, the molecular networks abruptly transformed their handedness.

this seems rather intuitive to me, and unsurprising.

for every action there is an opposite and equal reaction.

a spinning cue ball changes directions when it bounces off a rail.

it's the same reason circular polarizers let you see through reflections in glass.

> In biology, we know that even a single defect in DNA, a mutation, can cause a disease or some other observable change in an organism

And this would relate to material science?

A single defect can impact the entire field. One unambiguous result could throw the entire standard model out the window. It has happened in astronomy, the father of physics, multiple times.

>A single defect can impact the entire field

Just ask Boeing.

In the way that molecules are so fast that they go past each other frequently, making global effects possible to arise from small perturbations.

One thing that comes to mind is prions, which cause diseases like mad cow and CJD.

"Prions are misfolded proteins with the ability to transmit their misfolded shape onto normal variants of the same protein."

https://en.m.wikipedia.org/wiki/Prion

I think you and parent came up with a possibly better example than the one in the article quoted by the grandparent comment, more so than it being a clarification of how single DNA mutations ripple out to be big problems.

That's incorrect. Molecules collide when they are close enough. (There is a small probability of tunneling, but it's really small.)

Small perturbations in a crystal are call "defects" https://en.wikipedia.org/wiki/Crystallographic_defect and they are quite stable, and don't move too much. The effect is very local.

The defects in DNA can have a huge effect if they are in an (un)lucky spot, and they are completely unrelated to material science.

Basically, insofar as the perturbation does not impact more than the local lattice structure (sometimes just a few NM across), the overall lattice (therefore properties) will be rather unaffected. I know pure crystals will often have embedded impurities (ie: precursor residues in the product). The impact for the DNA change is that DNA is used to create downstream materials, whereas materials are generally used because of their properties directly. As long as a defect does not impact to a great extent the general properties of the material, it is irrelevant.

In terms of movement inside a lattice structure, the only real movement is vibrational and rotational movement, so global effects because of particles moving about has far lower influence.

Depends on the type of defect. Dislocations can move around quite a bit and they do affect the structural integrity of the material.

This is why if you bend a fork, you will never be able to fully unbend it (without heat treatment), there will always be a S-shaped bend it it.

an iron whisker with a single crystal defect in it has dramatically different macroscopic properties, especially tensile strength, from an iron whisker without a single crystal defect.

A Black Swan is an "unknown unknown", something you don't just lack understanding of, but don't expect or predict. The statistical interpretation of the term was popularized by Nassim Taleb in the book of the same name: https://www.goodreads.com/book/show/242472.The_Black_Swan

A black swan is not "an unknown unknown." It's something very rare, possibly non-existent - the phrase has been part of the English language for centuries (from Latin), and is clearly not being used in reference to Taleb's book:

> "This defect is like a black swan—something special going on that isn't typical," said Dr. Edwin Thomas, professor in the Department of Materials Science and Engineering

Yep. Even though related but the phrase "black swan" is different from the "Black Swan Theory".

The wikipedia entry[1] has the explanation of both. And the usage by Dr. Thomas certain refers to the phrase not the theory.

[1]: https://en.wikipedia.org/wiki/Black_swan_theory

The meaning of the phrase changed completely once black swans were actually discovered in Australia.

Did it though?

Isn't that the point? Before English-speakers had seen one, 'black swan' was a nonsense impossibility, like water flowing uphill. After Brits saw them in Australia, the phrase changed from 'total impossibility' to 'extremely unlikely but what do you know, actually true!'

Right..

Rather "Outside context problem"?

Related, but that's a subset of "black swan". Not every "black swan" is a problem.

I'm not sure I agree with anything you have said here.

"Black Swan" was in use before Taleb's book, at a similar frequency as it is today (Google Trends scores 2 vs 3, where 100 is when the book was released).

"Black swan" as a phrase dates at least to Roman times, often referring to the philosophical idea that the observation of a single black swan would prove their existence. (I've heard 'black sheep' used for this as well, although that has other more popular meanings).

The interesting part is that this did come to pass, for black swans: which are only native to Australia.

So, in my mind, it refers to something which is conceivable, but not believed to exist and not (yet) observed.

The Roman writer Juvenal is the origin of the phrase [1]. Neat to see pictures of them. [2] And humbling to think it took almost two thousand years for them to find out that the proverbial phrase was wrong.

[1] https://www.etymonline.com/word/black%20swan

[2] https://en.wikipedia.org/wiki/Black_swan

> "Black Swan" was in use before Taleb's book

In fact he likely used the term for his title because it's a well-known metaphor.

I still think it's a strange phrase. To me a black swan is a normal swan.

But until Europeans had come to Australia, no Europeans had ever seen a black swan

So if i see a black swan here in germany, this means it is a a descendant of an australian swan?

apparently so

[0] https://en.wikipedia.org/wiki/Black_swan_emblems_and_popular...

Grey geese though.

The term black swan as it appears on the book actually comes from a philosopher. I think it is from David Hume. Does anyone here on HN knows? Its basically the concept in science that the connection between cause and effect is an ilusion. I remember reading the thought experiment from a philosopher in that context. Since google stopped working finding these things has proven more difficult.

However, in this article it’s referred to as an actual black swan, not the concept in the book.

"actual black swan, not the concept"

2nd paragraph of article, first sentence: "This defect is like a black swan—something special going on that isn't typical,"

So how is this an actual black swan - a bird with wings... and not a "black swan" - an unkown unknown (as described eslewhere)?

What is the relevance of the term here?

This subthread is an illustration of the HN tendency to seize on whatever aspect of the article we think we can sound smart about, which, despite seemingly being an isolated comment that the scientist did not clarify or expand on at all, the journalist cleverly elevated to the headline.

Very good observation

You've just summarized the beauty that is n-gate.

That it's in the title?

GP is pointing out that it's being used incorrectly

except that, this being the Internet, the observation is not in fact correct.

(I think we've all been "guilty" of this at one point or another)

The term isn't used incorrectly

Black Swan event is always unexpected, unpredictable, with no prior recorded history of such event, so no one could prepare for such event. It's always catastrophic as a system couldn't be possibly ready for it.

Black swan is one of those terms no one can quite seem to agree on and people correct others corrections.

Kind of like np-completeness.

NP-completeness has a rigorous mathematical definition. People who know the field definitely agree on it, there's nothing fuzzy about it.

... and AI

And what is "soft matter"?

Matter is stuff.

Condensed matter is stuff that is not gas.

Soft matter is shorthand for soft condensed matter, which is stuff that is not gas nor solid.

Fluidics, liquid crystals, polymers are examples of soft matter.

Source: I am a soft matter physics PhD that focused on liquid crystal phase characterization.

The article seems is too shallow in details of their seemingly very important discovery. Atleast nothing I could decipher. What do you think is relevant in their finding?

Apparently swans are. I’d guess most birds, especially geese, since their feathers make nice pillows.

This has nothing to do with black swans, the birds... this has to do with unexpected results that are easy to explain in hindsight after the truth is known.

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

"Taleb's "black swan theory" refers only to unexpected events of large magnitude and consequence and their dominant role in history. Such events, considered extreme outliers, collectively play vastly larger roles than regular occurrences.[2]:xxi"

This discovery (unexpected behavior of matter) seems like it'll have a surprising and large magnitude.

The way they use the phrase here has nothing to do with Black swan theory or Taleb's book.

It just means something very rare, and that's been the common meaning of the phrase in English for hundreds of years. It comes from Latin.

But no correction of my improper interpretation of “soft matter”? ;-)

its early and the caffeine hasn't set in (still hasn't). I guess this is a better comment if I read it with a sarcastic twist?

from article....

"Materials can be broadly classified as hard or soft matter. Hard materials, like metal alloys and ceramics, generally have a very regular and symmetric arrangement of atoms. Further, in hard matter, ordered groups of atoms arrange themselves into nanoscopic building blocks, called unit cells. Typically, these unit cells are comprised of only a few atoms and stack together to form the periodic crystal. Soft matter can also form crystals consisting of unit cells, but now the periodic pattern is not at the atomic level; it occurs at a much larger scale from assemblies of large molecules."