TOM SCOTT: The Youth Winter Olympic Games
have brought me over to Lillehammer, in Norway.
It's still early in the season here,
so they are making snow.
Because getting these slopes to competition standard isn't easy.
ROGER HJELMSTADSTUEN: Here in Hafjell we have about 250 snow guns
They're all controlled from a big control room
and they all are connected together.
It's a lot about planning. To put the guns at the right place.
It's about wind, if you put it on the wrong side it's going to be a lot of snow in the
trees.
That's why we have two teams working night and day
the whole fall, the whole winter, to make sure everything is perfect.
TS: Here, in the snow gun, huge amounts of water and air
are being forced through tiny nozzles,
creating a fine mist that freezes into fresh powder.
But while the weather is cold,
the temperature is actually not quite below freezing here.
So why does this water freeze into snow?
Why doesn't it just... rain?
Okay. Physics.
As water evaporates, it sucks heat from the surrounding environment.
Put some water on your hand and blow on it,
and the wet part will feel colder
because that evaporating water is sucking the heat away from your body.
That's what's going on here.
Some of these water droplets evaporate,
so they drop the temperature around them.
Which means other droplets might start to freeze.
And once that's started, you get what are called nucleation sites:
the start of snowflakes.
And if it's not quite working efficiently enough,
then you can buy a kind of protein slurry.
You add it, very diluted to the water,
and suddenly every droplet is a nucleation site
and can form its own snowflake.
RH: To make snow, we have pipes for water and pipes for air.
On top of that, every cannon needs a computer cable.
The water here in Hafjell comes from big lakes at the top of the mountain
and from there it's natural pressure going down.
That's the easiest and least expensive way.
During a normal season, we use about 30,000 litres a minute.
It sounds a lot, but we have a big, big lake
so during the whole season it's about 5-10cm down
and that's if no new water is coming in
so most of the time, it just looks like it's not touched.
TS: The drier the air is, the more water can evaporate into it.
So if the air is really, really dry, 0% humidity,
you can make proper snow when the air temperature
is well above freezing, anything up to 6°C.
But if the air is humid, there is nowhere for those droplets to evaporate to.
At 100% humidity, when the air is saturated,
the temperature has to be -2 or lower to make snow.
'Cos this isn't some kind of instant magic freezer.
The laws of thermodynamics pretty much make that impossible.
Much as it'd be great to have a snow gun that works in the middle of summer
all you're going to end up with then...
...is a rainmaker.
RH: So, snowmaking is really important for big contests,
but it's also really important for just
the average day here in Hafjell with normal people.
It's what we need to make this mountain work.
Without it we'd be nothing. We need snow!
TS: There's a load more videos over on the Olympics channel
and on my channel, go check 'em out, go subscribe,
and thank you to the Youth Winter Olympic Games
for bringing me out here to Lillehammer.
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