Scientists still speculating what makes ice slippery

This one accidentally relates to the Olympics too, but only because there is a lot of ice involved with some of the events. Science Friday did a segment this week about what makes ice slick, but what I found interesting is that scientists still aren't entirely sure what allows us to skate, ski, or throw a big rock across it. The general consensus is that there's a very thin layer of water on top of the ice that reduces friction, but how that layer forms is contested.

The segment's guest, who is a mechanical engineering professor, explained that the reasoning in most physics books is actually wrong: they claim that the water is produced by the pressure created by the weight of the person (or curling stone) because liquid water is more dense than frozen water. In reality, it would take a lot more weight than the average skater to create the pressure required. Currently, there are two other possible explanations for the water:

1. Ice just naturally has a nanoscale layer of water on its surface (we're talking a thousandth of the width of a hair) that provides the slipperiness, or 
2. The friction generated from the initial movement generates enough energy to melt the surrounding ice.

The former may seem a bit farfetched, but it's been shown to exist even tens of degrees below freezing, so it helps to explain why we can slip on ice not only when it's super cold but even if we're not moving, which the latter wouldn't be able to account for.

Of course, in Sochi, the problem isn't making the ice warm enough to produce that layer (because it's already there…) but rather keeping the venues cold enough, between the subtropical location and the not-so-finished states of the facilities...