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>Certainly there are many unexplained effects in solid state physics Wait for it… Why ice is slippery? Usual explanation is completely incorrect. Actual semi-

by vl 4y ago

>Certainly there are many unexplained effects in solid state physics Wait for it… Why ice is slippery? Usual explanation is completely incorrect. Actual semi-conclusive research just recently happened.

hutzlibu 4y ago
It is not, because ice has a smooth surface and that probably the surface layer melts a bit because your shoes are warm? That would be my reasoning, but it likely seems to be wrong, well why?
- Sharlin 4y ago
  The usual hypothesis is that a microscopic layer of the surface melts, not because your shoes are warm, but because of the pressure. But the pressure is not enough to do that. That said, as anyone who has been in icy conditions can attest, it is clear that ice at ~0° C is vastly more slippery than at, say, -20°C.
  - darkerside 4y ago
    My understanding is that, at the borders, master is constantly changing between its states. A boiling pot has water molecules turning to steam, as well as vice versa. It just has more of the first probabilistically. Maybe the same happens with ice and water.
    - kortex 4y ago
      That's more or less it, as far as I understand. There's the hexagonal lattice of solid water ice, where hydrogen bonds form a 3D tetrahedral structure which is very stable. At the boundary, there are no molecules "above" the solid latice, so those water molecules are held less tightly. The exact dynamics are challenging to predict because we can't exactly see what's going on (most simulation based).
  - usrusr 4y ago
    The pressure from well distributed static load divided by area is not, but on the tiny scale where the difference between grippy and less grippy surfaces happens there isn't so much "well distributed" going on. And once you add lateral force to the mix all bets are off: there will always be a point getting better grip (is surface interference the correct term?) than others, see a local force concentration and when that causes a tiny spot of phase transition there will very soon be a new point of least local slippyness getting all the attention of lateral force.
  - hutzlibu 4y ago
    ", it is clear that ice at ~0° C is vastly more slippery than at, say, -20°C." There is nothing more slippery in my experience, than rain on the street, that just turned frozen. But ice at -20°C is usually older and has not such a smooth surface anymore, so hard to compare in non lab settings.
- skykooler 4y ago
  If that were the case, then cold things wouldn't slip on ice, but they do (for a demonstration, pick up a rock that's been sitting out in the cold and note that it still slides on ice)
  - rajamaka 4y ago
    Wouldn't that just be due to the low coefficient of friction?
    - FPGAhacker 4y ago
      > Wouldn't that just be due to the low coefficient of friction? You mean, its slipperiness?
  - __alexs 4y ago
    I'm not sure a cold rock sliding across very cold ice will slide any better than if the ice was another very large smooth rock. Ice is hard and smooth. Hard smooth things have low friction.
o_____________o 4y ago
You're talking about the "2D gas vs liquid" discussion?
kgc 4y ago
Link to the research?
emptybits 4y ago
I had to look that up. Here's research[1][2] from 2019 about "why ice is so slippery", including some of the apparent surprises. I dunno. I'm not a physicist so some of the surprises seem like very minor things to me. Spoiler: According to this research, ice is slippery because of a thin layer of water. (As we expected, no?) But the water layer is 1) thinner than expected, 2) more viscous than expected, and 3) contains bits of ice which help make it extra slippery. > "Usual explanation is completely incorrect." Only for an unusual definition of "completely" IMO. Again, IANAP. [1] https://phys.org/news/2019-11-ice-slippery.html https://phys.org/news/2019-11-ice-slippery.html [2] https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041025 https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041...
- m463 4y ago
  I remember listening to joe rogan when he interviewed neil degrasse tyson and he had some fascinating insights into the behavior of water with relation to pressure and temperature. I can imagine ice on an iceskate wanting to be solid, but because that takes up too much space it becomes a liquid instead.
- JumpCrisscross 4y ago
  > contains bits of ice which help make it extra slippery Wait, why would bits of ice make it extra slippery if it's the water that makes ice slippery?
  - lukas099 4y ago
    Maybe the ice molecules move through the water with less resistance, since the ice molecules are already 'tied up' in a lattice structure and therefore do not form as strong of hydrogen bonds with the neighboring water molecules.
  - coryrc 4y ago
    I assume like walking on marbles or ball bearings.
- dumpsterdiver 4y ago

by vl 4y ago

hutzlibu 4y ago

It is not, because ice has a smooth surface and that probably the surface layer melts a bit because your shoes are warm? That would be my reasoning, but it likely seems to be wrong, well why?

Sharlin 4y ago
The usual hypothesis is that a microscopic layer of the surface melts, not because your shoes are warm, but because of the pressure. But the pressure is not enough to do that. That said, as anyone who has been in icy conditions can attest, it is clear that ice at ~0° C is vastly more slippery than at, say, -20°C.
- darkerside 4y ago
  My understanding is that, at the borders, master is constantly changing between its states. A boiling pot has water molecules turning to steam, as well as vice versa. It just has more of the first probabilistically. Maybe the same happens with ice and water.
  - kortex 4y ago
    That's more or less it, as far as I understand. There's the hexagonal lattice of solid water ice, where hydrogen bonds form a 3D tetrahedral structure which is very stable. At the boundary, there are no molecules "above" the solid latice, so those water molecules are held less tightly. The exact dynamics are challenging to predict because we can't exactly see what's going on (most simulation based).
- usrusr 4y ago
  The pressure from well distributed static load divided by area is not, but on the tiny scale where the difference between grippy and less grippy surfaces happens there isn't so much "well distributed" going on. And once you add lateral force to the mix all bets are off: there will always be a point getting better grip (is surface interference the correct term?) than others, see a local force concentration and when that causes a tiny spot of phase transition there will very soon be a new point of least local slippyness getting all the attention of lateral force.
- hutzlibu 4y ago
  ", it is clear that ice at ~0° C is vastly more slippery than at, say, -20°C." There is nothing more slippery in my experience, than rain on the street, that just turned frozen. But ice at -20°C is usually older and has not such a smooth surface anymore, so hard to compare in non lab settings.
skykooler 4y ago
If that were the case, then cold things wouldn't slip on ice, but they do (for a demonstration, pick up a rock that's been sitting out in the cold and note that it still slides on ice)
- rajamaka 4y ago
  Wouldn't that just be due to the low coefficient of friction?
  - FPGAhacker 4y ago
    > Wouldn't that just be due to the low coefficient of friction? You mean, its slipperiness?
- __alexs 4y ago
  I'm not sure a cold rock sliding across very cold ice will slide any better than if the ice was another very large smooth rock. Ice is hard and smooth. Hard smooth things have low friction.

o_____________o 4y ago

You're talking about the "2D gas vs liquid" discussion?

kgc 4y ago

Link to the research?

emptybits 4y ago

I had to look that up. Here's research[1][2] from 2019 about "why ice is so slippery", including some of the apparent surprises. I dunno. I'm not a physicist so some of the surprises seem like very minor things to me. Spoiler: According to this research, ice is slippery because of a thin layer of water. (As we expected, no?) But the water layer is 1) thinner than expected, 2) more viscous than expected, and 3) contains bits of ice which help make it extra slippery. > "Usual explanation is completely incorrect." Only for an unusual definition of "completely" IMO. Again, IANAP. [1] https://phys.org/news/2019-11-ice-slippery.html https://phys.org/news/2019-11-ice-slippery.html [2] https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041025 https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041...

m463 4y ago
I remember listening to joe rogan when he interviewed neil degrasse tyson and he had some fascinating insights into the behavior of water with relation to pressure and temperature. I can imagine ice on an iceskate wanting to be solid, but because that takes up too much space it becomes a liquid instead.
JumpCrisscross 4y ago
> contains bits of ice which help make it extra slippery Wait, why would bits of ice make it extra slippery if it's the water that makes ice slippery?
- lukas099 4y ago
  Maybe the ice molecules move through the water with less resistance, since the ice molecules are already 'tied up' in a lattice structure and therefore do not form as strong of hydrogen bonds with the neighboring water molecules.
- coryrc 4y ago
  I assume like walking on marbles or ball bearings.
dumpsterdiver 4y ago