# Talk:1867: Physics Confession

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F1rst P0st http://www.explainxkcd.com/wiki/index.php/269:_TCMP 172.68.141.190 07:54, 24 July 2017 (UTC)

Fuckin' ice skates, how do they work? OldCorps (talk) 11:26, 24 July 2017 (UTC)

Any relation to #1489? They're both about things physicists don't understand. http://www.explainxkcd.com/wiki/index.php/1489:_Fundamental_Forces 172.68.132.5 (talk) (please sign your comments with ~~~~)

Explain physics: It's 'cause Randall's dumb. 141.101.104.47 (talk) (please sign your comments with ~~~~)

Explanation of skating

A lot of people both here and on Reddit seem to be talking about pressure of the skates reducing the melting point. Pressure of the skates can only reduce the melting point by about 0.5C, so this is clearly not sufficient to produce a layer of liquid below -0.5C. The more correct explanation is that there is an ever-present layer of liquid on the surface of most crystals, including ice - this is the best explanation that exists right now, and explains why ice skating stops being possible below around -30C (and is hard at intermediate temperatures). This is the explanation offered by most modern university courses on thermodynamics or materials science - here is an excerpt from a University of Cambridge materials science course: Excerpt Jaredjeya (talk) 13:03, 24 July 2017 (UTC)

I've just looked at the article linked in the explanation, whoever put it in didn't read the full article because it goes on to mention exactly this explanation. Jaredjeya (talk) 13:07, 24 July 2017 (UTC)
Good ol' circular reasoning. OldCorps (talk) 15:48, 24 July 2017 (UTC)

"...ice skating stops being possible below around -30C". Not true. I've skated at -40C. It's effing stupid, risk of frostbite in minutes, but still works. (Living North of 60 for 4+ decades) 162.158.74.219 (talk) (please sign your comments with ~~~~)

-40C? Ha! Try -40F! davidgro (talk) 23:55, 28 July 2017 (UTC)
Ice skating works because ice is slipery and skates reduces the surface touching the ice which reduces the friction increasing how slipery it is. However it is a special case of the question: "Why is ice slipery in the first place?" Which is not fully understood.162.158.114.16 11:27, 31 July 2017 (UTC)

A recent article discusses the ice skating things here. Looks like the confined melted water film behaves oddly (viscoelastically) and unexpectedly gains ideal lubrication properties for skiing and skating. Surface hydrophobicity also affects sliding coefficients not by changing the thickness of melted films but rather the local water (complex) viscosity. However they do not try this at -40 C (or -40 F as slyly pointed out above).