# Fun science: how does figure skating work?

How does figure skating work? In short, we don’t fully know. You may have learned in science class that the pressure of the blade causes the ice to melt. Water does have the unusual property that solid ice is less dense than liquid water, and ice will melt under sufficient pressure. The thing is, the weight of a human body on an ice skate isn’t enough pressure to induce that melting.

Phase diagram for water. At normal atmospheric pressure, water freezes (to ice I, or normal ice) at 32 F or 273 K. At higher pressures, the freezing point is suppressed, as shown by the solid black line between the blue and white regions at the bottom. (Figure credit, Wikimedia)

So, if not the weight of the skater, what allows the blade to slide along? Well, there is a layer of liquid at the interface of the blade which allows the skater to glide. Denizens of very cold climates know that at sufficiently cold temperatures, skates do start sticking and catching on the ice (source: my mom’s many winters in Wisconsin, and science). Our best guess right now is that the surface properties of ice differ from the properties of the bulk. Perhaps at the surface of ice, the pressure *is* sufficient to cause melting (at temperatures near enough to freezing).

The difference between bulk properties (the properties of a big chunk of something) and surface and scale-related properties is increasingly studied. Nano-scale gold exhibits a wide variety of properties depending upon particle size, as you can see in the image below. Such colloidal gold is used in a variety of medical applications such as tumor detection and drug delivery.

Solution colors change as the gold particle sizes change. (image source Wikimedia).

When things like water and figure skating are still mysterious, who says science doesn’t leave room for wonder? Given the relatively few forces interacting in such systems, I find the richness of variation we observe entrancing. This Olympics, I’ll watch the athletes skate and consider the angstrom-scale world on which our lives glide.

# Swimming at the Shore

Alas no, I am not swimming at the shore for some time. But I like to pretend that I might be soon, and so I wistfully mull through my photos. I love to swim, and anytime I visit non-lethal water, I want in. The next best option is photographing. The two mix poorly, but I try. Below are some lovely tropical beaches, and some gloomy beaches and some extremity-numbing fjord beaches.

As a point of pride, I did get in the fjord and swim to a dock about 30 feet out, but I was going numb. Because children are insane, several children also did and wondered why I minded. This summer I’m visiting the Outer Banks of NC, and hoping to try a little surfing.

Happy Friday!

Playa del amor in Cabo San Lucas.

Dungeness Spit on Olympic Peninsula in Washington State.

Sunrise in the Outer Banks of North Carolina.

The dunes of North Carolina at sunrise.

Swimmin in fjord water in Solvorn, Norway.

Shore birds of the gulf coast of Florida.