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Winning an alpine skiing race can come down to a tiny margin, so the skiers have to make sure they prepare their skis just right!

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The 2018 Winter Olympics is bringing together top athletes from 89 nations, and alpine skiing is one of its signature sports.

All athletes do what they can to get an edge, but for alpine skiers, even the tiniest edge counts because these races can be won by one one hundredth of a second. And sometimes, it all comes down to the right wax.

To maximize their speed, skiers want to have as little friction as possible between their skis and the surface they’re skiing on. Ski wax—which looks, feels, and melts a lot like candle wax—makes this possible. When you melt wax onto ski bases, they absorb it like a sponge.

As a skier skis, this wax gradually leaks out, providing a slippery layer between them and the snow. Seems simple enough. The hard part is picking the right wax, because the conditions for every race are different.

Everything from the day’s temperature and humidity to the wetness of the snow matters. The term ‘wetness’ refers to the snow ratio: the ratio of snow crystals to liquid water in a given volume of snow. Snow that’s considered “wet” has a low ratio of around 10 to 1: meaning for every 10 centimeters of snow, you get one centimeter of liquid water, which helps the flakes stick together.

Dry snow has a higher ratio, like 20 or 30 to 1, so it’s light and powdery. The closer the temperature is to 0 degrees Celsius when the snow falls, the wetter it is. And wet snow can stick to the skis, creating a kind of suction effect that slows them down.

To combat that, racers use a softer wax made up of more fluorocarbons, short carbon chains containing fluorine, which repel water better. When the snow is dry, its crystals can penetrate the bottoms of the skis, messing with how the ski glides. So in dry snow conditions, skiers use a wax that’s even harder than the crystallized water thanks to a greater proportion of hydrocarbons—long chains of carbon atoms bonded to hydrogens.

But it still isn’t as simple as choosing one or the other. These waxes come in slightly different formulations for different temperature ranges, and they can be layered to create the perfect combination. So there’s no miracle wax that’s the fastest every time.

A better wax selection for the day’s conditions can’t make up for a bobble, though—that’s racer speak for a mistake. But if a race comes down to hundredths of a second, a solid understanding of the physics of wax and friction could win the day. Thanks for watching this episode of SciShow, brought to you by our patrons on Patreon.

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