We FINALLY Proved Why Ice Is Slippery

Why is Ice Slippery? New research suggests we finally have an answer.
Source article:
www.nature.com/articles/s4158...
0:00 Why is Ice Slippery?
1:14 The History of Understanding Ice
2:15 The Pressure Hypothesis
5:41 The Quasi-Liquid Layer Theory
6:50 The Results
10:17 Cold Ice Isn't Slippery
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[@michaeldaniels3865]

It makes me wonder if these observations could inspire a "slippery" metal alloy that never needs lubrication

[@orchdork775]

Interesting!

[@fireworkstarter]

youd need a metal alloy that wont ever rust since that would not make it pack propperly into a crystal again and it needs to be able to turn liquid again under pressure

[@dtibor5903]

Yes, that metal is bronze... Although it needs some lubrication for best performance. You find bronze bushings in small motors and fans.

[@pon1]

PLEASE someone invent that!

[@SeekingTheLoveThatGodMeans7648]

Any alloy would be slippery at its melting point. A bearing filled with a liquid like mercury (or safer, galinstan) -- as long as it could be made so that it would not leak its liquid and its temperature never reached the freezing point of the liquid -- might be a possibility.

[@flaym.]

Therapist: "double-bonded hydrogen isn't real, it can't hurt you" Double-bonded hydrogen: 6:25 (right side)

[@bananasnapples9465]

what is that abomination

[@HighFlyer96]

Don't kink-shame, just a different kind of -bondage- bonding

[@helohel5915]

Hydrogen bonding:

[@terraminator4379]

erm what the sigma?

[@oa_math]

lmaoooooo I see it now lmaoo

[@antivanti]

As someone who lives "quite far north" I can attest to the fact that ice gets less slippery when it's REALLY cold. Bur also if the soles in your shoes are cheap and contain more plastic than rubber they get hard as bakelite and insanely slippery. Also if it's really cold and there's a slight layer of powder snow on perfectly blank ice you're screwed. There's no more slippery surface in the world. Literally no friction. It's like being the puck on an air hockey table 😅

[@blucat4]

I believe you. But coming close is a hard rock road (graded flat and smooth) with clay over the top (also graded smooth) and rain. That's extremely slippery as well.

[@Myron90]

I live quite far south. It's always so hot.

[@nomars4827]

​@@Myron90you live not as much far South. Really far South is also cold

[@_apsis]

@@Myron90 you live quite far middle, then

[@Padraic54]

I can't hear the word bakelite without having flashbacks to End of Evangelion.

[@Min0rus]

This is just a meme compilation of people slipping on ice. You cant change my mind

[@manfromlamancha]

They know what they were doing.

[@thunderhorse64]

With a bit of science and history sprinkled in there for a bit of flavor

[@cosmicraysshotsintothelight]

So are the comments... and they are crystalizing and accumulating... Snow flakes and Ice cubes and glaciers, oh my! No wonder they carved out lakes. The slippery side is 'up top'!

[@zachhoy]

his editor is low-key awesome

[@Patrik6920]

well thas some cold hard slippery news..

[@S1nwar]

do you know why, when you wet your fingers with a tiiiny amount of water you get insanely good grip (on a smooth metal surface for example)? completely dry fingers are slippery and completely wet ones too but theres that perfect amount of water that gives you an insane amount of friction

[@cyfralcoot65]

The answer is probably capillary forces pressing your hand and a surface together. Just lay 2 flat glass sheets on top of each other and add 1 drop of water between them - You'll be surprised how much force is required to pull them apart

[@MrTheoJ]

this is also the case with some types of garbage bags. With dry fingers its hard to seperate / open them but with damp, not wet, it's easy

[@itssoaztek4592]

@@cyfralcoot65 Yes, capillary forces contribute to improved "grip". A much bigger contribution though comes probably from the increase in contact area. Imagine two sheets of any solid material put on top of each other. The force required to separate them decreases with increasing surface roughness, i.e. decreasing contact area. In other words, the sum of attractive interaction forces between these two surfaces in contact depends strongly on the number of atoms (per unit area) at very close distance across the "gap". Now, instead of polishing two rough surfaces you get a similar effect here by adding water to "smooth out" the roughness, i.e. increase the "contact area". An indication that the contribution of capillary forces is not as big may be derived from the fact that compared to wet fingers you get a similar effect of improved grip with "greasy" fingers. Grease or fat are semi-solid materials, so capillary forces are not existent or negligible in that case. Of course, this is still not the whole picture but hopefully a useful illustration.

[@jaspermooren5883]

Just a hypothesis, but it might have to do something with the oiliness of your fingers. By applying water, the oils on your fingers are rendered less effective. I wouldn't be surprised if there is an optimal point between reducing the effectiveness of the oil and the effect of the liquid water itself. But like I said, that's just a hypothesis.

[@bl4cksp1d3r]

That's because of the grease on your skin. Clean the properly and this happens way less

[@seanb3516]

I had a Chemistry Teacher demonstrate a Solid - Solid Chemical Reaction. It was quite odd looking. Two different white powders were placed in a glass tube. The tube is shaken only one toss at a time. In the tube blue crystals quickly formed. The crystals grew each toss of the tube but not otherwise. There had to be mechanical motion and contact.

[@DoNotPushHere]

Won't you remember which solids were those? Looks like an amazing experiment

[@kleinegeist]

But seriously, if you recall the chemicals involved I'd love to know, might duplicate the demonstration.

[@vari1535]

i would like to add to/reinforce the inquiries about which solids they were!

[@trs4184]

With the utmost reverence, I, being the fourth person to inquire, humbly beseech you to graciously reveal the esteemed identities of the two venerable white powders that were utilized in this noble undertaking, so that I might fully grasp the intricate details of their application and import.

[@andrewmcguinness1845]

I, too, wish to humbly add my name to the list of others requesting this knowledge of you. I seek their import and subsequent application for the entertainment of my 4 year old niece. Even if she isn't entertained, I will be. EDIT: My research indicates it might be some form of Copper Sulfate.

[@Yezpahr]

Lol, the bloopers at the end were priceless. Here you are trying to prove something mundane that we all know happens and the ice gods just aren't letting you have it.

[@dmitryshusterman9494]

Not proving, explaining

[@michaellavery4899]

Sounds like most of my experience chemistry labs. I'm sure bronze age people were better practical chemists than me.

[@HallowedError]

This was fantastic and I remember all the old videos that basically said 'this is our best guess but it doesn't actually make sense' so this was really satisfying

[@pauljackson3491]

So the AFM is actually like a really small record player stylus. And with the laser bouncing off there are 2 levers involved: The stylus is one and the laser beam is the other.

[@oscargr_]

With a rather odd definition of lever, sure.

[@cosmicraysshotsintothelight]

Paint It Black (ha ha) and the beam will apply 'pressure'. Hey... I know! Apply a Vanta black surface treatment. Oh crap, then you will not be able to see the laser bounce! I suddenly hear David Bowie music in my head... I am getting old.

[@entcraft44]

@@cosmicraysshotsintothelight The beam will exert more pressure (twice as much to be exact) if you make it nice and shiny rather than black.

[@admthrawnuru]

The explanation in the video is oversimplified, but sure. The actual paper used non-contact mode AFM, meaning the tip oscillated just above the surface and the atomic force was derived by modulation of the amplitude or frequency of the oscillation

[@SuperBoppy]

The world's smallest phonograph player. LOL

[@ralphc.644]

The "I" in ice Ih and Ic is the Roman numeral one. It should be pronounced "ice one h" and "ice one c". Fantastic video! Great work!

[@scott98390]

Yet another example of font failure

[@confuseatronica]

Ith Icth Ith bronounthd li yuh tug ith frothed sthoo a flagpole

[@killerbee.13]

@@scott98390 there is no font that will show you the difference between a roman numeral one and an I

[@apotatoman4862]

@@killerbee.13 U+2160 edit: Ⅰ

[@chromatica__]

@@killerbee.13 technically there is a separate Unicode character for the roman numeral "Ⅰ" that isn't the same as the latin alphabet capital I, but because people pretty much always just use the latin alphabet I for both and most fonts don't have the roman numeral version so it doesn't really matter

[@bujin5455]

4:15. I don't know that I buy the idea that there are three square inches of ice skate on the ice when a person is in motion. (The area required for a 150lb person to be exerting 50psi.) I suspect the real expressed area is quite a bit less than that.

[@Bob94390]

How wide is the blade of a skate used by figure skaters? 0.4 centimeters? It is curved, so less than the full length is in contact with the ice; say 5 or 10 centimeters. Based on these assumptions, the contact area could be around 2 to 4 square centimeters. That is a factor 5 to 10 less than 3 square inches. So I agree with you.

[@elirane85]

@@Bob94390 To bottom of an ice skating blade is not flat but concaved so the width that touches the ice is much much less then the blade's width, it's actually 2 very thin blades that you skate on called the "inner edge" and "outer edge".

[@ldcent8482]

I agree, but I gave up after googling for lengths and widths of hockey blades and receiving exclusively articles about blade radius, which is apparently a keyword. I say, take the blade length and multiply by the width of a cunt hair times two.

[@cosmicraysshotsintothelight]

@@elirane85 It is all touching. Those "edges" are what are there and are "sharp" (concave face) to allow the skater to use his down force and that cutting edge and the skate blade tilt angle and skate blade lengthwise arc to effect a turn or vector alteration. The racing skates have a flat squared face on the edge, which is one reason why they step through turns on their tracks and use big long body weight shifts and not a convex curved edge kick to accelerate against. Even in the case of the concave faced blades the entire blade face 'touches' when 'gliding'. Like the difference between 'riding ' a skate board and the leg kicks to get it going and keep it going.

[@velisvideos6208]

The third skate profile is found on ice yacht blades. These are sharpened to knife edges with about 90 degrees angle. The blade must be slightly curved for best performance with a short flat centre section. It's noteworthy that in practice speed skates have a similar 90 degrees effective angle on the edge that touches ice. Based on personal experience, smooth ice is slipper than rough ice. For safe walking on smooth ice the worst conditions occur when there is a thin layer of dry snow covering the ice. It's like walking on roller bearings.

[@uumlau]

Awesome video! The interesting thing is that the "it melts slightly under pressure" explanation was parroted as fact for so long. There's an old Feynman video (1986-ish) where he gives that explanation.

[@Yezpahr]

What I find weird is how it managed to get parroted that much, because the notion that it melts a fine layer on top under pressure is still just a circular argument. You end up with a layer of water but why is **that** slippery? They (the people in the past, aka before this video) couldn't explain it other than saying "the water is slippery, not the ice", which is slightly true but in fact it's the individual molecules that have no fixed lattice to adhere to. Even Feynman fell for it, which makes me feel quite a bit better about myself when my teacher (elementary school 4th grade) gave the same explanation and I kept saying it was a circular argument because it's not explained why the water is then slippery.

[@ClementinesmWTF]

@@Yezpahrwater…is slippery tho. It’s not a circular argument to say water is slippery. Everyone knows that a thin sheet of water acts as a lubricant and is slippery, hence “wet floor” signs and hydroplaning. You really weren’t as clever as you thought you were and this seems more like a r/im14andthisisdeep type brag.

[@1dfr33]

​@@YezpahrI've never in my life heard a 4th grader say "circular argument" or even have the wherewithall to properly follow an argument in a way that could allow them to state that. With that being said, I'm calling cap on you homie.

[@Yezpahr]

@@1dfr33 In my country we actually got education, instead of 4 years of kindergarten.

[@Yezpahr]

@@ClementinesmWTF Your reddit lingo is meaningless here. They didn't explain water was slippery, they just said it was. I do occasionally grab a drop from the faucet to gain **friction** on the garbagebags when getting it off the roll and to open a new bag... so it is slippery you say, but there are more forces at work as to **why the ice** is slippery in the first place which nobody explained until these papers came out.

[@fulldeepshadowmmon]

This is a perfect illustration of the problem with active measurement. The energy introduced to the system to measure it changes it. Therefore what you are measuring is the system plus the measuring method. So you can never measure just the system.

[@user-vp1sc7tt4m]

Are you making a reference to the QED measurement problem in your statement?

[@michaelhart7569]

Yes. That sort of question was always in my mind when reading/reviewing AFM-type experiments (I was working with surface plasmon resonance at the time). Also, more than one supervisor reminded that "remember, this is their best data they are publishing". Asking how often another pattern was observed tended to make people get a bit scientifically defensive.

[@MeriaDuck]

I knew about electron tunneling microscopes, this looks a slight bit simpler than that. The fact that we can scan atomic-scale resolution is mindblowingly fantastic.

[@thea78999]

If you are in an AFM Lab and the people there are in a mood to do it, ask them to scan graphene with one. It can manage to produce incredible pictures where you can clearly see the graphene structure (iirc we managed do get a frame of 3 by 3 nm). Also AFMs can be used to probe for magnetic fields (for example it's possible to visualize the data written on the disks of old harddrives) or you can graft polimerized surfaces and do very fine engravings.

[@admthrawnuru]

atomic-scale AFM is fairly difficult, by which I mean you need the proper setup. Like all atomic-resolution methods right now, it mostly only works at cryogenic temperatures in vacuum... but more generally easy-to-use AFMs can still get nanometer order resolutions and can be modified to measure all kinds of other phenomena (conductivity, work function, magnetic moment, piezoelectric effect, etc.). Liquid environment AFMs also operate at slightly lower resolutions and can pick up electrochemical signals and the like. My second most cited publication (sadly not first author) was used electrochemical microscopy to detect analyte activation on sensing nanoparticles.

[@Hiandbye95]

​@@admthrawnuru Why does it have to be so cold? Is it because at higher temperatures the atoms move around too much?

[@retu3510]

I know a reasearch group who just uses a platinum wire which they cut off at an angle with scissors and then pulse current through a few times till they have a one atom tip. Works quite well for their use case and was quick

[@thea78999]

@@Hiandbye95 (I can only tell from own experience.) With graphene we didn't need a vacuum or cryogenic temperatures. Essentially the tip of the cantilever was send rapidly across a small area of the graphene. This does produce pictures of the graphene structure, but they aren't the smoothest. Essentially the scan lines would be slightly off the nexts position. I assume it's possible to do much better under cryogenic temperatures in a vacuum and it may be needed for materials other than graphene (seems pretty plausible to me).

[@rebeccawinter472]

The background baseline of "under pressure" and "ice ice baby" is just sublime when talking about vacuum @2:20.

[@holderheck]

From what i have personally noticed below -34C i can't find anymore slippery ice.

[@blucat4]

Very cool experiment, cheers. 🙂

[@vez3834]

That could be due to how your shoe behaves at that temp. There are probably other factors you'd need to keep in mind.

[@holderheck]

@@vez3834 Not just on my shoe, it's hard to explain but by touch with any object, metal flesh, rubber, fur doesn't matter you can feel in how it slips one feels like cheap chalk on a chalk board and when it's warmer it slides.

[@DumbAsh00]

What I personally noticed is below -34C I can't find anymore water

[@Arahknid]

Okay, now, why is water sticky?

[@AUTISM.GAMING]

It causes bonds on almost every object, basically, it is literally trying to be part of you, this is because the positive and negative charge on the H2O molecules.

[@4D2M0T]

Maybe surface tensions

[@pourplecat]

it simply just sticks to things

[@Victorsandergamer]

​@@pourplecatlmao how is that a sufficient or even satisfactory answer in the comment section of a science channel? what's your reasoning... the H20 molecules have the same properties as glue? (which involves water EVAPORATING, mind you) or the individual atoms grabs onto things with tiny little electron arms?

[@goofycat676]

@@Victorsandergamerbro does not understand a joke

[@solii01]

I started watching this video with the thought "I will probably not understand this". But you explained everything _very_ well. Good job and thank you!

[@JohnDlugosz]

Two ice cubes fresh from the kitchen at -8 degrees C act more like proper solids and don't stick together when pressed. Interestingly, they also _sound_ different when knocking against each other. However, they are still slippery, and if I drop one it will shoot off along the floor. Also note that in winter sports, a colder ice rink is "faster" for skating.

[@NotSomeJustinWithoutAMoustache]

He mentions and explains this in the video.

[@blucat4]

The colder they are, the more like proper solids they act.

[@JohnDlugosz]

I notice in the out-takes that you had trouble getting it to stick together, too. I'll bet they were fresh from the freezer; too cold for that trick. It works when the ice is at equilibrium, actually melting to maintain the freezing-point temperature of the rest of it.

[@xqr2911]

You all should google "gauge block wringing" to see that "proper solids" stick to each other easily but must be very very very flat.

[@lodewijk.]

Wow, it's not often that I get to see such a big common mystery definitively solved! Major kudos to the researchers and to you for breaking it down so clearly

[@AlbertScoot]

3:17 Thank you for voicing something everyone who's studied engineering has felt.

[@gruffdavies]

Brilliant video. My favourite of yours so far (as a fellow PhD physicist, I really appreciate how much work you've put into researching this and loving the cheeky humour too. This new explanation of a classic phenomenon that we thought we understood reminded me of a fairly recent result showing that static electricity (e.g. amber and fur) isn't due to electrons as we thought, but molecular ions. Apparently, a chemist proved the electron model was energetically impossible. A bit embarrassing for us physicists, but I bet he was a physical chemist, so we can take the win anyway 😂). Keep up the great work, Dr. Ben!

[@TehPwnerer]

Skate blades are not in the shape of a point like a typical knife but are in a concave curved C. This way each side has its own edge to grip into the ice better for turns etc.

[@TjarkVerhoeven]

Icehockey and figureskating blades are. Speedskating blades are flat with 2 90 degree angles.

[@dallassukerkin6878]

One of those topics that turned out to be much more interesting than you would imagine! Learning that certain ice-based sports have temperature preferences was a real "Really?" moment :)

[@MrTheoJ]

It is my understanding that wooden-shoes ( yes I'm Dutch ) are anti-slippery, the question ( if true ) is then why?

[@peetsnort]

The fridge workers in old capetown used clogs

[@aukir]

Wood fibers absorb the water and freeze, kinda micro gluing you to the floor. It's really an amazing process, and not only that, it's completely made up.

[@rafox66]

Do you walk on clogs regularly? Because I can tell you that's not the case.

[@cosmicraysshotsintothelight]

@@aukir Stand in one place on a cold enough day on ice and with cold enough clogs and they will "seize in place". Maybe some of the superglue you were playing with got onto your eyelids. It is really an amazing process.

[@peisrijn]

I never walked on ice with them, but almost always experience snow sticking to their soles an building into a sort of snowball unterneath that walk very awkward, until it breaks of after getting 5-10 cm thick. This is at temperatures when the snow is sticky as you experience in the Netherlands.

[@barberb]

> Physics grads: why is ice slippery > CS grads: how can I make sand think

[@RENO_K]

😂😂

[@RENO_K]

How do i make sand do my earthly bidding

[@cosmicraysshotsintothelight]

OK... now try that with the grains of dust in a bag of flour.

[@colbyboucher6391]

Or crabs. They started to make crabs think, once, that was fun. Crabs computer.

[@cosmicraysshotsintothelight]

@@colbyboucher6391 Coconut crabs! New drone 'firmware'.

[@firestarter5239]

icy what you mean

[@PodaKalidoka]

IC it 2

[@poldidak]

Icy what you both did, there!

[@blucat4]

@@poldidak They're pretty cool!

[@rogerneedham8775]

You can c yourself out

[@PodaKalidoka]

@@rogerneedham8775 😂

[@robmorgan1214]

Metals will also fuse if they have a surface of sufficient flatness and they do not have an oxide layer. Infact, most metallic machine parts that require fasteners like screws or bolts will use different metals to prevent a weld forming when the faster is tightened.

[@SeekingTheLoveThatGodMeans7648]

The blocks of ice fuse when pressed together in air that is above their melting point, because their surface first melts then resolidifies. Try doing that in air below the melting point and at the least enough pressure would be needed to correspond to a pressure weld.

[@xqr2911]

You can definitely do that without melting or much pressure with other solids - like metal in room temperature. The surface just needs to be extremely flat - look for "gauge block wringing".

[@TerryBollinger]

What a fantastic science video! For the first time in my life, I feel like I’ve heard a genuinely plausible explanation for why ice is slippery! Thank you!

[@Dumb-Comment]

0:14 ok, then explain why my cat is glued to my legs

[@danielthecake8617]

uhhh... electrical attraction?

[@romainvincent7346]

Asking such questions is a slippery slope

[@Tferdz]

AFM probes are rarely metal, usually made of silicon or silicon nitride. Metal probes have lower resolution and higher wear, so they're often metal-coated instead. 7:30

[@unclejimmy7]

Is silicon not metal?

[@genericalias5756]

​@@unclejimmy7metalloid no?

[@ratdoto2148]

@@unclejimmy7 It's a metalloid.

[@cosmicraysshotsintothelight]

@@ratdoto2148 They should use some of the crystal they grew to make the new kilogram standard. Now that is some clean crystal (probe) candidate material. I think the tips are grown not machined though, right? So... oh well.

[@ratdoto2148]

@@cosmicraysshotsintothelight What? The Kilogram is now based on a fundamental value, it never changes. Why would you change it back to some physical nonsense?

[@Amadioh]

took us long enough

[@hannosolo]

Us?

[@cuboembaralhado8294]

​@hannosolo humanity

[@hannosolo]

@@cuboembaralhado8294Birging.

[@vez3834]

​@@hannosolo what are you on about?

[@Lex-uq1yj]

Friction playing in the background when you talk about friction, cheff kiss

[@night_san03]

Prior to watching: my theory for why ice fuses the way it does comes from thermal exchange and re-freezing. Simply, the ice is able to absorb just enough heat from the small amount of surface liquid to re-freeze it, ultimately ever so slightly increasing the rate at which the exteriors of the chunks melt. Kinda like a heat ripple.

[@kevinconnolly3600]

I spent some days this January in Rovaniemi where the temperature was between -15C and -30C but the ice was not slippery. It was quite safe to walk around with no risk of sliding. I wonder if that was because of a rough layer of frost or snow covering the ice?

[@peetsnort]

A couple of years ago I drove from Hereford to Worcester in minus 17 the road was very grippy

[@cosmicraysshotsintothelight]

I topped Snowshoe Mt in PA USA one year on the expressway in 8 inches of snow. On the Eastern side of the incline to the peak, myself and truckers, etc. were passing cars in the fast lane doing the full (fool) speed limit in slushy snow at the road surface level. As I topped the hill (these ain't mountains)the Western side was wind blown powder ice as they had plowed away the snow before, and my car did three huge donuts in the middle of the three lane highway and as it did I saw all the cars backing off like some time slowed cartoon, and then my little Chevette went off the side of the highway and the shape of the ditch flipped the car once in the air and it landed in the wheels facing the road perpendicular to it no glass broken, no tires popped, and still running engine. I turned it off. Good thing because the exhaust pipe had broken free from the last mount and got bent and shoved into my gas tank. All the flip did was rack my hatchback open and threw my drafting board and some of my tools out into the 8 inches of snow, which is when I noticed the gas gurgling out. Glad I turned it off. Ice is very slippery and I doubt seriously that there was any liquid form water involved on that western side. The roadway was cold(er), and they plow so no salt or they missed this patch. Anyway, that is but one of my experiences with ice. They also took out several teeth on another occasion. How quaint.

[@nomars4827]

​​​@@peetsnort hm that's quiet explains how they confidently drive in Northern countries while when we have ice at close to zero temperatures it is tooo slipery.

[@timsoft3]

i'm so glad you've explained what I was never convinced of at school, about it being pressure melting the ice at the junction. It could never explain to me how you could have antarctic ice 1km thick wher if it was pressure due to weight, it would have to be liquid after a short depth. thankyou!

[@dennis1954]

Water changes phase into ice at 32F and ice into water at 32F in a freshwater lake. The heat measured as BTU are the difference. Water is the densest at 39F at is at the bottom with 38F rising as well as 32F water rising and freezes at the surface. That’s why there is water under the ice. Never thought about it but the water must apply pressure to the bottom of the ice holding it up as it expands. Not sure of saltwater temperatures due to salt changing the melting (phase change) point.

[@CrankyOtter]

@@dennis1954Salt amounts vary melting/freezing temperatures of water but the reason for Fahrenheit’s zero point is that’s where salty sea ice freezes. There have been refinements to precision subsequently, but 0°F = frozen ocean 32°F = frozen fresh water ~100°F = body temperature

[@erasmus_locke]

Insane that speed skaters could physically FEEL how slippery I've is and knew what temp to use

[@kcStranger]

So, I was actually in a graduate research group that studied the quasi-liquid layer using simulations. I think it's been general knowledge that it exists for quite a while, but the specific experiments that you showed here were new on me, and gave me a deeper appreciation for what's going on! I've been out of the science world for a while, and it's always fun to check back on the progress that's been made.

[@Jack.Waters]

Yes, Always fascinating that Water has no lubricity at all... Water instead of Oil in an Engine will lock it up Fast. And Ice is colder when in Water. Ice in itself is highly slick the more smooth it is. New Ice is very strong compared to being a week old on a Lake. 1" of new ice will generally hold a careful human: 3" of old ice. 10" of ice will hold an 8-ton truck. Drive too fast on ice and a Wave will occur. Fascinating stuff.

[@renerpho]

It's such a weird substance.

[@Jack.Waters]

@@renerpho I think it is also the only thing that swells as it’s chilled.

[@renerpho]

@@Jack.Waters One of very few that do that, yes. He mentions Bismuth, which also does it. All the other examples are synthetic, and don't occur in nature.

[@Jack.Waters]

@@renerpho thank you for that. You’ve cause me to research which feeds the mind well. Gallium also expands 3%. Fascinating that all 3 freeze at close-ish temps but they Boil at vast temps. Awesome.

[@user-js9tx6dz6y]

What a fun video. Learning while watching people slipping on ice.

[@z-beeblebrox]

I’m really glad I learned about this because the “pressure causes a thin film of water to form” always seemed like such a letdown.

[@Werewolf.exe77]

As a hockey player who never liked its slippery because of its wet answer, I have to say this was a Bangger video very well spoken and very well explained, god bless man.

[@Matt-kl1pg]

How do they make the AFM probe tip so thin?

[@alquinn8576]

not sure about AFM but I did use a scanning tunneling microscope in a physics lab and made the atomic-scale tip myself. how? by taking a metal wire and wire cutters and cutting the wire while putting it under tension. it was surprisingly easy to do (though some people were less good at it, and had to try a few times to get a good tip). I'm guessing the AFM used here was more precision than that, but the ductility of metal allows for easy creation of a sharp tip.

[@SDelduwath]

Depends on the style of probe. Lithography for standard silicon ones and possibly combined with selective ion etching. Fancy geometry probes typically done in a FIB (painstaking and tedious). For high Q AFM probes I mostly used electrochemical etching though: fine wire(tungsten or gold) as anode with a platinum wire ring cathode in KOH solution and use a comparator circuit to shut off the current the moment the wire breaks which gets you into the single digit nm range.. which is small but doesn't quite hit clean lattice pics. For that you need a cold sample and an even sharper tip which typically is done by functionalizing the tip and putting a carbon monoxide molecule on the end to use as a probe tip.

[@lagautmd]

You didn't cover it, but this appears to explain why two pieces of ice join to make one piece when pressed against each other. Those molecules at the surface that are free to move now have 'buddies' on the other surface and they can arrange into a continuation of the hexagonal pattern, creating a single sold. I don't know if it has been verified, but it certainly seems reasonable based on this explanation for slipperiness.

[@velisvideos6208]

If one were to make skates with blades from water ice, would they be slippy or sticky?

[@lagautmd]

Skates from ice? Sticky, of course.

[@gglovato]

¿could you cover on why some materials like graphite and molybdenum are so slippery too?

[@AuroraIceFlame]

1:35 that’s certainly what I’ve thought all my life. Interesting how something that seemingly would have such a simple answer is actually not at all. This is why I love science!

[@AllHailZeppelin]

Veritasium’s been real quiet since this vid dropped

[@jmi967]

Why doesn't an AFM probe tip dull immediately on use?

[@Yezpahr]

Because "touch" and "feel" are an oxymoron in the explanation. You will never touch atoms. Not even with other atoms. You press within its electron shell and get bounced back before the electrons touch anything. This force is so tiny yet so fast that nothing truly touches each other. (well, unless you overcome the force of that electron shell which basically only happens inside a star or neutron star and perhaps in cyclotrons)

[@aspuzling]

An AFM probe doesn't really "touch" the atoms that it's sampling, it rests a fixed distance away from the surface and senses the change in electromagnetic force on the tip caused by the electron cloud surrounding the atom. When it detects close separation, a feedback mechanism automatically moves the tip away from the sample and so the separation is restored to the fixed amount. This way you can move over surfaces that are not perfectly atomically flat without damaging the tip.

[@BeaglzRok1]

@@Yezpahr The thing about this fact that I find funny is that it means a person's sense of touch is created by cells registering ratios of resistance and energy from nearby magnetic fields rather than any actual contact between matter. 50-grit sandpaper has very prominent peaks of magnetism with rigid support behind it (solid) surrounded by a much larger amount of magnetism with no support (fluid) that give the impression of something jagged. It also means you've never physically contacted anything with your atoms, even your own body's atoms. Compounds might be tugged out of place by particularly resilient structures, but it's not like they were attached by anything more than chemical bonds.

[@jmi967]

@@aspuzling I didn't realize that it was actively moved, which makes way more sense. All I could think of is how a diamond knife works but how easy it is to destroy the edge if you even slightly move it to one side.

[@jmi967]

@@Yezpahr Bet you feel special knowing that. In reality, touch applies to electromagnetic field repulsion, and therefore applies here. Your comment would be like me taking a hammer to your car and saying “well technically I didn't touch it”.

[@spoookley]

i’d imagine that some strand of asbestos could potentially be sharper than an afm probe, given that sharpness is determined not just by how thin the tip is, but also by how long the shaft is

[@AntiSwagCorp.]

sus

[@OminimonHD]

man... this video made me emotional for some reason lol, there is just something special about actually fundamentally discovering the WHY of something.

[@benmcreynolds8581]

I never stop being fascinated by Material science and all the unique ways people keep coming up with advancing our technology to study these material properties. It's really impressive how people have come up with the most ingenious ideas to build new devices to measure or visualize materials.. It almost feels like we discover a sorta cheat code to the world whenever certain discoveries get made..

[@coldicecubes0]

I'm not weird >: (

[@illyon1092]

this was a great video, excellently explaining this newfound knowledge in a great format without wasting time. I also appreciate the subtle, unobtrusive bits of dry humour throughout.

[@Magikarp_With_Dragonrage]

I KNEW IT, I've been saying that it probably worked like this for years(6 or 7), I'm glad its confirmed now so i can stick it to that one science teacher who told me i was wrong!

[@chilael6892]

I'll never forgive you for not including that clip of the guy sliding in ice without falling for a solid 15 seconds lol

[@Rick_Cavallaro]

Using "Under Pressure" at 2:20 was brilliant. But now I want to see you use "Ice Ice Baby" since it ripped off "Under Pressure".

[@Sonny_McMacsson]

They're totally different!

[@nonstop7243]

He did use it, it's the first song played.

[@Rick_Cavallaro]

@@Sonny_McMacsson here's what the elders of the interwebs have to say on the topic... Ice ice baby under pressure Sampling and Controversy “Ice Ice Baby” by Vanilla Ice is a song that has been shrouded in controversy since its release in 1990. The song’s bassline is heavily sampled from Queen and David Bowie’s 1981 hit “Under Pressure”. The controversy surrounding the song’s sampling and the lack of credit or royalties given to Queen and Bowie has been a topic of debate for decades. Queen’s Reaction According to Freddie Mercury’s assistant, Peter “Phoebe” Freestone, Freddie Mercury initially thought he was listening to “Under Pressure” when he first heard “Ice Ice Baby”. He seemed bemused more than angry, and later said “imitation is the sincerest form of flattery”. However, the members of Queen were not always kind when talking about “Ice Ice Baby”, with drummer Roger Taylor quipping “A white rapper from Florida… great” and guitarist Brian May admitting his view of the whole thing had been jaundiced because rap didn’t appeal to him. Impact on Vanilla Ice The controversy surrounding “Ice Ice Baby” had a significant impact on Vanilla Ice’s career. The song’s chart-topping era was short-lived, and he soon faced embarrassment and mockery for his handling of the situation. He was accused of ripping off Queen and Bowie without giving them proper credit or royalties, and the controversy surrounding the song has followed him for decades. Legacy Despite the controversy, “Ice Ice Baby” remains a iconic song of the 1990s and a staple of hip-hop culture. The song’s sampling of “Under Pressure” has been widely discussed and debated, with some arguing that it was a clever and innovative move, while others see it as a blatant rip-off. Regardless, the song’s impact on popular culture is undeniable, and it continues to be a topic of discussion and debate to this day.

[@Rick_Cavallaro]

@@nonstop7243 I missed it. I am shamed and shall self-administer the appropriate punishment!

[@oceannuclear]

@@Sonny_McMacsson I suppose "ripped off" was not the right term, but the bassline of Ice Ice Baby samples Under Pressure's.

[@rokasb9441]

Now add new MIT research, pointing out that water evaporates not just from lack of atnosphere or from heat, but also from sunlight...

[@lovecontemplation8607]

That is a weird gripe on the pressure-issue even if it doesnt explain it. It would be around 400.000 pascal pressure, for a person m=80 kg. Standing on both skates. That with atmospheric pressure is around 500.000 pascal. It’s a huge pressure, but not enough to make a real dent in the melting pressure point given by the graph.

[@andyrbush]

That was educational and hilarious at the same time. Absolutely brilliant.

[@Nibor999]

Water: Is there anything it can't do?? A fascinating video. Thanks so much.

[@johncage5368]

I like explanations that dig deep enough to actually explain something on a molecular level. Nice!

[@glennback3105]

Dude you blow my mind every time. How much research u do is great and the vids too

[@blazerdc25]

Just an interesting fact, the blade of an ice skate isn't like a knife against an ice, more like a concave lens with the edges sharpened. Love the video!

[@AndrewJohnson-oy8oj]

What an amazing time to be alive. We've both created macroscopic devices that can interact on a microscopic scale while also affecting the planet on such a massive scale as to destroy ourselves.

[@WowOafus]

In your skate animation, the blade appeared to have one point, as if it was a knife blade. I wanted to clarify, in case you weren’t aware, that ice skates have two points of contact each. They are basically two blades connected by an arc. The shape of that arc ranges between 3/8” to 1 1/4” radius. Most hockey players get a 1/2”-5/8” cut. I ref hockey in my free time, so I go with 5/8”-3/4” depending on how soft the ice is. Shallower cuts allow for more gliding, which is better for reffing as we aren’t constantly vying for the puck. We can usually glide into our positions. Hockey players also have the length of the blade cut as a radius of a circle depending on if they are going for more acceleration and maneuverability or want more top speed and stability. I use a 13’ radius for the blade length, as flatter blades cause less fatigue, and I’m sometimes on the ice for 12 hours(8 games) in a row. Some players will have a length radius of 7’. The science behind skates and what goes into it is amazing. If you have any questions about it, I’d love to answer them.

[@m.j.nilsson]

I have not tested any of this stuff, but my logic would go as follows: A smooth surface vs a smooth surface is slippery and if the object is large enough, it traps a small layer of air and makes these objects hover for a while and then creates a vacuum as the air escapes between them, but if there's water between any smooth material, it becomes extremely slippery. Two ice blocks in a room temperature are already melting and when connected the surface has no room for heat and they both distribute their coldness causing them to fuse. Ice skate on ice creates grooves and is again the smooth vs smooth surface making it slippery. Cold ice block vs cold ice block in a cold room would have friction between them if the surfaces are not smooth. If you would rub these ice block against each other, they would find some sort of equilibrium on their surfaces and be evenly smooth and then become slippery. Snow can become ice under pressure and if you step on ice with snow under your shoes, the snow will turn harder and match the smoothness of the ice. If the ice is smooth; the snow under your shoe will also become smooth and very slippery. Interesting subject and I could write a lot more, but thank you for the video and anyone crazy enough reading my entire text.

[@Gunbudder]

4:04 NO! This is NOT the shape of ice skate's blade! its a very specific cupped shape with two edges on the sides and its actually raised in the center of the blade. this forms a channel of water created by the pressure. the single pointed blade in this video's graphic doesn't work as well

[@maxfinnian]

This would be functionally identical though? The air in the n shape is not trapped, so effectively it is two V shapes next to each other. Functionally it would be equivalent to a V with surface area 0.5A when the skate is angled and A when the skate is flat. The two Vs would help more with balance but do little else to the physics (anyways, this would lower the calculated pressure reducing the effect of pressure melting further than originally expected).

[@diskdrive123]

That was a complicated way of saying that ice's surface acts like a liquid, but only when in friction.... 🙄

[@LuggageStardate]

It actually doesnt. They add weights to vehicles when they drive on ice.

[@diskdrive123]

​@@LuggageStardate I don't even know what that is suppose to mean in this context?

[@hancocki]

I love how you sampled the classic "Under Pressure" riff! 😊

[@user-yz6rw3si3e]

I remember learning in Physics in highschool about ice skating being dependent on the phenomenon of regelation. Later on we learnt that this example was erroneous, but it is still being used as an example in lower classes.

[@isodoublet]

Nope not buying it. If this is supposed to be "the" explanation for ice slipperiness, there better be some direct evidence that this is actually what happens _when things slide on ice._ A static AFM image taken in a regime where ice isn't even supposed to be slippery to begin with doesn't quite cut it. Furthermore, if this is the explanation, why would two ice blocks fuse when touched? It'd be very unlikely that the H and C surfaces would align perfectly on two random ice blocks, so you'd still expect them to slip. Also, when you lightly touch an ice block, it sure feels more frictiony than when you actually try to slide it with force, so there's definitely a pressure-dependent effect that this explanation is missing.

[@jordonhope3408]

OMG thank you for posting this! It's great! Experience tells us that pressure melting IS happening for skate blades... the trail left behind a smoothly gliding skate blade is very obviously shaped like a refrozen liquid. You've quoted a pressure of about 50 psi... but your source seems to misunderstand the size of the contact patch between blade and ice. Since the skate blade is rounded in the z-axis and sharpened to a point in the x-axis, the contact patch is theoretically infinitessimal in size, and the exerted pressure is therefore infinite. (Practically speaking though, we're probably talking about one square micron for the contact patch, and the pressure at least sufficient to re-freeze the layer into ice-VI). But that reasoning never explained hockey pucks and gumboots slipping on ice, and it always bothered me. But now we know!

[@BraindeadCRY]

Water is just an insanely interesting material. It breaks so many expectations, deviates from so many rules, yet we as a species are so used to interacting with it in all it's forms that we mostly just take these strange properties for granted.

[@TehPwnerer]

Lots of materials will slip, metals do along internal grain boundaries as you bend them. Water is apparently also slippery along it's grain boundaries but instead(or also?) on its surface where Ih & Ic meet & weakly bonded atoms fill the gap.

[@JessWLStuart]

WOW! I've always wondered about this! Thanks for presenting it!

[@tomkimsour]

I hate how international system is not used in the video. Other than that it was a very interesting video, well paced and structured. Thanks for the video!

[@Yorick257]

I find it fascinating how the "slipperness" is different from person to person, activity to activity, and science to "real" world. This winter we had two major temperature periods. -2 to +2 C and -10 to -6 C. And the first one was the reason I bought spikes for my shoes. I fell several times, once into a puddle. But as soon as the temperature went below -5 (and -7C being the most slippery ice is according to this video), I could walk and even run freely, without any risk of falling!

[@zerokun2655]

3:27 jeez man don't jump scare me like that, my chemistry professor asked me to draw that graph and it completely slipped (pun intended) out of my mind the second he asked...

[@coorooegan4508]

I wrote a pop-sci book years ago where for maybe a page, I talked about slippery ice and how it had been puzzling people for, well, quite some time. I find it particularly awesome that they actually figured it out (we're so living in the future :)

[@rebelliousfineart8202]

You make it sound so complicated but everything you just said basically took me to the same conclusion that I had already drawn in my head and that even in it’s solid form there are molecules moving freely on it’s surface.

[@PlayNowWorkLater]

Mind blown! This was one of the most articulate and concise science education videos ever posted on KZbin. Thank you for putting this video together.

[@wstoker84]

Hockey players like colder ice which would have more friction for quick and powerful movements due to almost no water on the surface. Speed skaters mostly cold because the ice has enough water on the surface to be slippery but not too much to slow them down. Ice skaters like just slightly cooler than freezing ice because the extra water provides a cushion making the ice soft. Makes sense now.

[@jlyn8228]

When I was seven walking home from school I came across a frozen pond, it was kind of slippery but I wanted more. I dumped my waterbottle all over it then proceeded to eat the ice. Walking home I kept thinking why it do that. Completely forgot about it after I found we just got a ps2.

[@mattball420]

Some ice is pretty grippy, like more so than grass, gravel, dirt etc almost sticky

[@shmayazuggot8558]

Brilliantly presented, although a complex journey you captained us through the waters with clarity. Earned a new subscriber here!

[@Cajundaddydave]

Awesome! We have observed this pre-melt layer in black ice which is typically at the ideal temperature for friction to vanish. A few degrees warmer or colder and friction is restored. Adding a layer of sand to the steps or driveway on the night before an ice storm gives our boots something to hang on to when the pre-melt layer is most treacherous.

[@JulesStoop]

4:02 the shape of the part of the blade touching the surface is actually somewhat concave along the entire length. So it’s not a sharp ‘V’-shape as shown in the illustration, but an upside down-very shallow-‘U’-shape. Which results in two parallel ‘lines’ of maximum pressure.

[@TurtleWaxed]

Another thing to consider is that when ice is very cold such as -40F (not counting wind chill), you can't slip and cant skate on it. Trust me, I tried it when I was a kid. Yes my parents made sure I dressed warm and let me try even though they told me it would not be fun. I i still had fun and proved it to myself. I put my skates on and gave it a run thinking I would just coast and ended up almost into a face plant, and it was an amazing thing to learn, as a young boy, trying to figure out why his skates and shoes gripped like the ice was made out of sand paper. (I deduced that the ice was so cold that I was freezing to the ice instead of the ice melting under the pressure of my weight). I was about 12 yrs old when I discovered this :)

[@Aranimda]

Thanks. You finally answered a question I had as kid. The answer I got was that the ice melts a bit because of the friction warmth and that the liquid water generates the slipperiness. And that the water refreezes so fast that you can't see it. (When skating) I always doubted this a bit because any other smooth surface (Like metal, plastic, ceramic) that is wet gets slippery, but not nearly as slippery as ice does. But because I did not have a better explanation I accepted it. Problem is still that your answer is so complicated that I can't explain it to anyone else.

[@lHawkel]

Slippery aside, the fusing property is pretty common to me. Metals do the same, that’s how welding work. We heat them to liquid, and they fuse before cooling down back to solid. Same thing happens with ice.

[@prometheusprime2004]

Any object in motion stays in motion unless acted on by another force. Friction is the reason we don’t slip - it’s what made rubber tires revolutionary. Lack of friction on ice is the cause of slipperiness, I would’ve assumed.

[@Dartheomus]

On a different but somewhat related note, I believe silicone oil has such a low coefficient of friction for a similar reason. The trimethylsiloxane groups on the end of the chains have almost no barrier to rotation when they spin. They are like little fidget spinners on the surface, and their mobility facilitates the movement of objects over their surface.

[@aajjeee]

About the AFM, you can also vibrate it extremely close to the atoms without contact and still have a meaningful reading

[@shorgravan]

Real interesting stuff! Double points as this made me unlearn something I thought I knew. And it as this generates a bunch of follow--up questions too! Can't access the paper right now but I'll definitely give it a read at some point.

[@SirLightfire]

4:58, if it's not a water slip layer caused by compression Then my best guess is an effect similar to graphite. Maybe the ice flakes into sheets, and those slide across each other

[@r0kus]

A related question would be, "Why is black ice slipperier than normal ice?" This is ice that sometimes forms on roads, often at dawn, that is so slippery you cannot walk on it, and vehicles lose a good portion of their ability to control direction.

[@Green0Photon]

What a crazy cool microscope type

[@C_Corpze]

This is weirdly fascinating. I used to think that ice was simply slippery because it's surface tends to be smooth creating minimal friction or function similar to oil.