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TOM SCOTT: The Youth Winter Olympic Games

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have brought me over to Lillehammer, in Norway.

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It's still early in the season here,

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so they are making snow.

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Because getting these slopes to competition
standard isn't easy.

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ROGER HJELMSTADSTUEN: Here in Hafjell we have
about 250 snow guns

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They're all controlled from a big control
room

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and they all are connected together.

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It's a lot about planning. To put the guns
at the right place.

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It's about wind, if you put it on the wrong
side it's going to be a lot of snow in the

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trees.

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That's why we have two teams working night
and day

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the whole fall, the whole winter, to make
sure everything is perfect.

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TS: Here, in the snow gun, huge amounts of
water and air

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are being forced through tiny nozzles,

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creating a fine mist that freezes into fresh
powder.

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But while the weather is cold,

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the temperature is actually not quite below
freezing here.

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So why does this water freeze into snow?

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Why doesn't it just... rain?

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Okay. Physics.

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As water evaporates, it sucks heat from the
surrounding environment.

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Put some water on your hand and blow on it,

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and the wet part will feel colder

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because that evaporating water is sucking
the heat away from your body.

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That's what's going on here.

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Some of these water droplets evaporate,

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so they drop the temperature around them.

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Which means other droplets might start to
freeze.

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And once that's started, you get what are
called nucleation sites:

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the start of snowflakes.

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And if it's not quite working efficiently
enough,

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then you can buy a kind of protein slurry.

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You add it, very diluted to the water,

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and suddenly every droplet is a nucleation
site

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and can form its own snowflake.

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RH: To make snow, we have pipes for water
and pipes for air.

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On top of that, every cannon needs a computer
cable.

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The water here in Hafjell comes from big lakes
at the top of the mountain

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and from there it's natural pressure going
down.

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That's the easiest and least expensive way.

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During a normal season, we use about 30,000
litres a minute.

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It sounds a lot, but we have a big, big lake

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so during the whole season it's about 5-10cm
down

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and that's if no new water is coming in

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so most of the time, it just looks like it's
not touched.

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TS: The drier the air is, the more water can
evaporate into it.

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So if the air is really, really dry, 0% humidity,

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you can make proper snow when the air temperature

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is well above freezing, anything up to 6°C.

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But if the air is humid, there is nowhere
for those droplets to evaporate to.

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At 100% humidity, when the air is saturated,

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the temperature has to be -2 or lower to make
snow.

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'Cos this isn't some kind of instant magic
freezer.

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The laws of thermodynamics pretty much make
that impossible.

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Much as it'd be great to have a snow gun that
works in the middle of summer

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all you're going to end up with then...

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...is a rainmaker.

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RH: So, snowmaking is really important for
big contests,

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but it's also really important for just

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the average day here in Hafjell with normal
people.

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It's what we need to make this mountain work.

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Without it we'd be nothing. We need snow!

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TS: There's a load more videos over on the
Olympics channel

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and on my channel, go check 'em out, go subscribe,

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and thank you to the Youth Winter Olympic
Games

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for bringing me out here to Lillehammer.

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