The Tap Root hosted a packed house at the latest Anchorage Science Pub event. The topic: the physics of snowflakes and skiing fast. The snow hasn’t reached Anchorage yet, but as the temperature drops the mind turns toward images of fresh powder and ski wax. This month’s presentation was beyond timely.
Dr. Travis Rector launched enthusiastically into the presentation’s first half, focused on the physics of snow and how it forms. Lest there be confusion about his feelings on the topic, he proclaimed “snow is the most freaking awesome substance on Earth.” Rector, a professor of physics and astronomy at the University of Alaska Anchorage, was comfortable in front of the crowd as he took the audience through the lifespan of a snowflake.
Snowflakes start out as dust particles gathering water molecules around them as they fall to the ground. The shape of a snowflake depends largely on the amount of humidity and temperature, resulting in myriad variations of hexagonal structures. The hexagons are formed when the bent-elbow-shaped molecules slow down and link up into ice crystals, which you can view in the graphic below.
scoffed at dispelled the theory of “water memory,” which is that a snowflake melted and then re-frozen would regain its original structure. Melted snowflakes turn back into water molecules, and when they are frozen they turn into frozen water molecules. In the slides of the different shapes of snowflakes, he showed an image of artificial snow. (It’s not as pretty.) Essentially, artificial snow feels and acts differently from normal snow because it isn’t made up of snowflakes at all.
As the subject shifted from the structure for snow to the enjoyment of snow, Alaska Pacific University and Junior Nordic Ski coach Dylan Watts stepped up to the mic. Initially a little fidgety, Watts visibly relaxed as he warmed to the topic of “why snow is slippery and how we can have fun with that slipperiness.”
Skiing is essentially the use of the low friction of snow to move across it quickly. Watts explained the slipperiness of snow is affected by its moisture, compression strength, purity of minerals and dust, and even electrostatic charge. This is one of the reasons that waxing the bottom of skis becomes so important. Ski wax comes in different levels of hardness, and acts as a lubricant between the skis and the snow. It’s not the most important thing, but it can be a very important factor.
“With the wax, that maybe only makes up three percent of ski speed. And that three percent, say if you’re doing a fifty kilometer race (the men’s field has a fifty kilometer race), in two hours. So [for] 120 minutes, three percent off, well, that’s six minutes you can really feel out of the race.”
The structuring of layers of wax on your skis allows the friction of the snow to shear the wax without causing drag on your speed.
Interestingly enough, Watts also noted humanity’s long history of skiing, which archaeology suggests we’ve had for around 10,000 years. He said this means skis “potentially predate the invention of the wheel by about 3,000 years.” (Though some regions of the world probably had more use for one than the other.)
Attendees responded well to the event and gave both speakers an enthusiastic ovation. They stuck around to answer audience questions ranging from “why is snow white?” to “how many kilometers can I get off a layer of wax?” Rector will be back next month to talk about “The Aesthetics of Astrophysics: The How and Why of Astronomical Photography.”
You can’t live in Alaska and not understand the importance of snow. It’s part of life here, whether it comes to sliding on it for entertainment or hefting it in shovelfuls out of driveways. One couldn’t help noticing the sideways glances out the window, checking to see if the termination dust had made its way any further down from the peaks of the Chugach range.