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- Hacker News
- This neural network stuff does give me real divination vibes, not gonna lie.by Ericson2314
- Sadly paper is behind paywall. But I question the choosing of the water model to be a 4-site, and why that specific 4-site one (TIP4P) instead of others that have shown to be more accurate such as OPC. Also, there seem to be previous experimental work (https://arxiv.org/abs/1304.2877) showing some evidence that apparently is not even referenced in this new paper. I wonder how does that compare, if at all.by mefistofeles
- Your linked preprint has been also published in Nature Communications: https://www.nature.com/articles/ncomms3401by roflmaostc
- So the OTA firmware updates on my dehumidifier for when they discover a new kind of water will come in handy after all!
- Nah, IFIFY: So the OTA firmware updates on my dehumidifier is for when they make a new kind of dehumidifier that they want me to buy!
- Dehumidifiers will end up being more efficient in one mode. When the manufacturer creates the new ones, a firmware update moves all legacy devices to the less efficient mode.by aljgz
- I wonder if we are finding structure here because we are looking for structure.
Similar how you can find human faces in random pixels or rocks.
by fooker - But what if we find the exact same face in different rocks or pixels? I also think the researchers were aware of this issue as the article mentions they were careful not bias their model.
Very interesting point though!
by hks0 - Nah.
If I understand the article correctly, they found a phase transition reaction, a chemical reaction that occurs in liquid water below 0 C that splits the body of liquid water into one continuous region of high density and one of low, so its no longer a uniform liquid.
This would also release heat, like the freezing reaction (and unlike random rearrangements of molecules in the liquid).
by hedgedoops2 - "Density is greatest at 39F, not 32F"
But density at "greatest" would mean volume shrinking...right?
I don't understand the article's logic.
by cellular - Yes, exactly. Water occupies the least volume per unit mass (equally, per unit molecule) at 39F. As it cools further, it paradoxically begins expanding in volume (as the polar ends seeking out their opposites in other molecules introduce a loose order to the liquid randomness).
Then, suddenly, at 32F/0C, water's real miracle happens. All the loose molecules click into place with other molecules - well, nearly all, because ice cubes aren't monocrystalline, typically, but those spare unmatched ends of molecules at crystal interfaces are still trapped by their other ends, and any single molecule unable to "find" a match for either strongly attractive end will still be trapped as well into solid-matrix mechanics. At most, those solo unmatched molecules become slight diffaction points for phonons (sound-energy propagation), but they are in fact so rare and so slight that they are generally undetectable. (The crystal faces are made of millions of unmatched molecule ends, and have therefore much more effect.)
Other polar molecules can act similarly, but water is astoundingly smaller than most others - so its molecules "find" their matches more easily, as they don't need to "rotate" much mass to line up - and is much less flexible as a result (so the alignment on the two-molecule level forms a more rigid body than, say, a polar sugar, and the volumetric effect is more pronounced).
by IAmBroom - > Much of the evidence for the LLPT has therefore come from computational studies.
So it's just a numerical simulation with some ML techniques?
by akomtu - a couple of breadcrumbs regarding the molecular organization of water.
Dissecting the hydrogen bond network of water: Charge transfer and nuclear quantum effects[2024]
https://www.science.org/doi/10.1126/science.ads4369
Resonance Character of Hydrogen-bonding Interactions in Water and Other H-bonded Species[2005]
by rolph - Could someone explain why raising standing water temperature to boiling, I see a constant stream of bubbles forming at the bottom of pan and floating up? Was there air between the water molecules to begin with? Any articles to help explain? I understand the obvious phase transition to gas which would escape at the top, but cannot quite grasp how we get the trapped air at the bottom.by jzer0cool
- Disclaimer: I am not a physicist and this is merely semi-informed speculation by an amateur enthusiast of understanding physical phenomena.
I had assumed that those were steam bubbles, not air bubbles. At high enough temperatures water becomes a gas. In a boiling pot, the highest temperatures are at the bottom. Temperature fluctuations on the bottom would lead to more steam production in some areas than others.
Any point at the bottom of the pot that did form a steam bubble would immediately lose energy to the steam and cool down. Now we likely are thinking of metal pots in this exercise, and metal conducts heat very well, so that cooled down point in the metal would draw nearby heat from the pan towards it, decreasing the chances of bubbles nearby. This would presumably lead to bubbles forming at some reasonable distance from each other, as any bubble formation causes the nearby pot metal to cool down.
Once in steam form, the steam bubble has a harder time losing energy. The energy was gained through direct contact of water with metal, but steam is much less dense, and it seems like the high-density shell of water around the steam bubble would act more like a mirror - reflecting the kinetic energy back into the bubble. This would keep the bubble stable as it travels up.
That's been my mental model of it for a while. It would be cool if someone who studied this stuff for real opined on it though.
- Yes it's the dissolved gas in the water that comes out, see: http://scienceline.ucsb.edu/getkey.php?key=3197
- >The boundary between them is thought to terminate at a "second critical point." This deeply supercooled region is so hard to study experimentally because water crystallizes rapidly
This sounds like the type of thing that could be used for some future technology that doesn’t exist yet and I can’t comprehend. Some sort of process that takes advantage of being in this second critical state.
- > some future technology that doesn’t exist yet
This is not usually how technology progression works when you see it play out.
More likely, it would be something like a 2% more efficient refrigerator. These advances stack up for a hundred years and build into something that looks like magical future technology.
There were very very few exceptions to this in history.
by fooker - Study published in Nature Physics: https://www.nature.com/articles/s41567-026-03301-8by wglb
- This is a molecular dynamics (with a specific TIP4 water model) and AI. I would characterize this paper (and basically most MD/AI simulation) as "guided hypothesis generation". I am skeptical that this result will hold up to experimental validation. It is incredibly easy to generate molecular dynamics results that look perfectly reasonable but have nothing to do with "reality" (i.e., how a lab experiment with the same system would turn out.)
One of the biggest challenges with water is modeling proton transport (i.e. pH, as water is a weird self-ionizing material.) Protons move too fast for MD steps to be stable, so they have to be approximated in some way. That is one reason why there are so many water models to choose from. Each model has a trade-off that is fine in some contexts, disastrous in others.
My money is on a TIP4 artifact.
- There's plenty of experimental evidence for similar things. That's why I made a comment on this earlier about how it relates to it. Check my comment or https://www.science.org/doi/10.1126/science.aec0018 or https://www.nature.com/articles/ncomms3401by mefistofeles
- Somewhat related is the hydration shell around molecules especially proteins. It’s been shown that semi structured water around proteins help guide molecules to reaction sites. Water is an amazing thing!by le-mark