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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

[2] https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041...

5 comments

Exactly, this it’s the new research. Standard (incorrect) explanation is because ice melts because of the pressure from the object put on it. Robert Wood showed it to be untrue at the beginning of the twentieth century, but “popular scientists” didn’t get the memo.

> Only for an unusual definition of "completely" IMO.

Agreed. While the "usual explanation" may lack the details that actual testing provided, deduction and logic in this case were pretty much harmonious with the findings. The water layer being thinner or more viscous than expected doesn't invalidate the basic assumption, and that's where all science starts, right? Some basic, yet to be disproved* assumption.

> 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?

I assume like walking on marbles or ball bearings.

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.

Ice isn't slippery, water is. If anything I'd say ice is actually pretty sticky. A very cold ice cube will easily stick to your skin.

That's just because your skin has water molecules that freeze on contact with the ice cube. If you use tongs to put an ice cube on your desk, it doesn't stick at all, right? And the friction is very low so it's easy to kick away -- things like a leather wallet stick much better to your desk.

I've not tried it but intuitively I'd expect it to slide about as well as other very hard things of the same shape.

I've dropped ice cubes on the floor before and they definitely slide a lot more than most objects of the same shape.

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.