Hello, my name is Nige.
And this morning on Imagine This, I'm awake really early.
It's still dark outside.
I don't always get up this early.
But today, I wanted to see the sunrise.
It's cool.
Yeah, I can see my breath.
The sun's coming up.
I can hear birds.
The grass is all wet.
It's a bit slippery.
Why is it wet?
Hmm, maybe it rained last night?
Nah, that's dew.
Well, do you know what?
We've had a question about you.
Hi, my name's Edward and I'm seven years old, and I would like to know why is the dew on everything in the morning?
How do you think the dew gets there? gets there with rain.
The rain makes it drop down.
From water evaporating, maybe.
In cold places.
From the drains.
Maybe.
Thankfully, I do know who to ask about Dew.
Nate Byrne.
I know him.
He's a weatherman.
He's a weather forecaster, I think.
Yep.
Nate is a meteorologist.
That's a weather scientist.
And Dew is all to do with weather.
Great idea.
Hold on a sec and I'll get him on the blower.
Hello, Nate speaking.
This better be a weather emergency.
I'm very busy.
Nate?
Hey, it's Nidge.
Nidge, my favourite physicist friend.
Any chance you're free to come and answer a science question about dew?
Hi Nidge.
Hi everyone.
That was fast.
Hey, you got here so quickly.
You know I never pass up the opportunity to talk about weather.
Yeah, I know.
We were wondering... Why is there dew on everything in the morning?
Where does it come from?
Well, dew can happen at any time of day, but the conditions have to be just right.
And that tends to be early in the morning.
What's dew made from?
Is it this water?
Yep.
Dew is just water.
But a single drop of water is made of billions and billions of tiny little water molecules.
Molecules.
They are so small you can't see them.
They're in the air around us all the time.
There's water in the air?
But I don't need a scuba suit to get around.
Thankfully not.
That's because water is very special stuff.
It can come in three forms.
It can either be a solid.
Water is ice.
Ice.
Ice.
In the North Pole.
Uh-huh.
It can be a liquid.
In my shower.
River, stream, ocean.
From a pool.
Like when you drink water.
Exactly.
Or water can be a gas.
Like.
Like steam?
Not quite.
Steam is technically still a liquid because it's made up of enough water molecules clinging together to make tiny water droplets.
Steam comes from trains.
When my parents are cooking on the stove and the steam comes out of the pots.
Yeah, but when water is a gas, it's invisible.
We call it water vapour, and that's what's floating around us in the air all the time.
It's sort of weird, but also normal.
Wow.
What's dew?
To see why dew gets on everything in the morning.
We could hop into a water molecule and follow the journey.
You game?
Yeah!
Hang on, you want to fit all of us in just one teensy-weensy minuscule water molecule?
We have to use our imagination.
Ah. course.
Sorry, I forgot.
All righty.
Three, two, one.
Here we go.
They're floating in the air.
Look down.
The ground is a billion miles away.
Hey, another water molecule just stuck to our one.
Water molecules love each other.
When they meet up, They hang on really tight.
Oh, pass this.
And then stuck to the other side.
Whoa, that's three water molecules.
Are we becoming a water drop?
Sorry, Nige.
Three molecules does not a droplet make.
We are at least a few billion short, I think.
Whoa, look around us.
I can see water molecules floating everywhere.
Hey, what are they?
Air molecules.
Just like water, air is made up of tiny little bits.
Look, over there, there's a bit of nitrogen.
And duck!
Mind the carbon dioxide?
Whoa, air's got a lot of stuff in it.
That's right.
The way air molecules move and behave changes at different temperatures.
This has a big impact on water molecules.
Let me show you.
But first, I'm going to need to fast forward our clocks to the warmest time of the day.
Hold on, everyone.
We're going for a ride.
Whoa!
Whoa, the sun is moving really fast.
It looks like that snail is breaking the speed limit.
We're zooming through time.
It's sunny now.
Hope you're wearing your hat.
It's the middle of the day.
What's happening out there?
The air molecules are going wild.
When the air warms up, the tiny air molecules get excited.
They literally start bouncing off the walls because they can't contain their energy.
Mum says I do that sometimes.
It is hard to sit still when you're excited.
Hey, the air molecule just hit us.
It knocked off our friends that it stuck to us.
We're back to being just a single molecule.
Yes, the air molecules zip around in the heat and then bump into the water molecules and break them up.
Even though the water wants to keep holding on to each other, the air keeps getting in the way.
And all of that jostling and bumping is what keeps water molecules up in the air.
Look, there's more molecules now.
Where did they come from?
Warm air can carry more of them.
It's a bit like juggling.
The faster your hands move, the more balls you can keep up in the air. equals faster molecules.
It's like yippie yoppie.
Hey, get out of it, oxygen.
Where's all this water coming from?
Well, all over.
Puddles on the ground rivers lakes, swimming pools, wet washing on the line and even the sweat on your skin.
It's called evaporation.
I'm starting to feel all hot and sticky.
It's so humid.
Yeah, the air feels sticky because it's full of water being juggled around by the air molecules.
I'm too hot.
Too hot.
I don't want to bounce around anymore.
No problem.
I can help with that.
Let's wind our clocks forward to a much colder part of the day.
Just before sunrise, I reckon.
We'll see what happens to all these busy molecules.
Whoa, the sun's going down.
Fastest sunset I've ever seen.
The street lights are coming on.
I think we've just gone past my bedtime.
Whoa, it is pretty chilly now.
I'm freezing.
And falling.
The air temperature's dropping and so are we.
Nate, why is our water molecule falling down?
Is this rain?
No, we're still too small to be rain, but this is the key to making dew.
Hang on tight!
Everything's slowed down.
Hey, all the other water molecules are crowding in around us.
I feel squished.
Move over, please.
In cold air, molecules stop moving around as much.
The air molecules don't have enough energy to break up the water droplets anymore.
They can't hold them up.
It's like the water molecules are huddling together in the cold.
Yeah, water molecules love getting together.
We're pretty tightly packed.
Can you make some room, please?
Please?
They're joining up with us. happened?
Where are we?
Enough water molecules joined up.
It made them turn from water vapour, a gas, back into a liquid.
On a plate of grass.
We're due.
The water needs something to grab onto to become due.
So you'll usually spot it on grass or stuff that's been left outside overnight.
I got drops on my bike.
I saw one.
On my neighbour's house.
To sit at the bus stop.
Our trampoline always has it.
That's it.
We call this process condensation.
It's just the opposite of evaporation.
And it happens down here because the ground is the first place to get cold at night and there's stuff around for the water to grab onto.
She has a lot of water molecules cuddling.
Yeah.
I love being here.
This feels great.
We're molecule mates.
Not the gassy gang.
We're in the liquid leagues now, but dew doesn't last for long.
What's going on?
The water molecule's jiggling.
While they're heating up, they're getting energy.
Yep.
The water molecules are flying again.
They're evaporating.
Remember, it's the opposite of condensing.
So the heat from the sun is adding its energy.
The air is speeding up again, starting to knock off those water molecules, turning them back from a liquid into a gas.
What does that mean for us?
We're flying again.
Hang on.
We're not stopping.
Uh-oh.
Nige, we're getting pretty high up.
Uh, Nate, we're past the treetops now.
Is that a bird? it a plane?
Remember there's water all through the air but as we go higher the air gets colder.
So that means the water molecules will stick together and will become dew again.
And land on grass.
No grass up here but this speck of dust looks pretty good.
Dust?
Yeah there's Lots of microscopic dust floating around in the sky.
We could condense on that.
Hey, more water molecules are sticking to us again.
Ah, welcome back.
Are we re-duifying?
Is that even a word?
Remember, water loves getting together.
When the invisible water vapour attaches onto dust high in the sky and more and more of the molecules come and cling together, they grow bigger and bigger and turn into something you can see.
It's clouds.
Clouds.
Clouds.
We're turning into a cloud.
We're like a marshmallow in fluffy bits.
So clouds are sort of like sky dew?
Oh, I'd never thought of it that way, but yeah, I suppose.
So dew and clouds are both condensation, the molecules in invisible water vapor joining together and changing into a liquid.
We can see clouds are liquid.
Yep, and you know what happens when they get too heavy raindrops they rain, you got it.
Us weather lovers call it precipitation.
Oh no, this cloud is looking like it's about to burst.
Oh, That sound reminds me.
I've got to get to the studio and tell everyone that there's wet weather on the way, so they don't forget their umbrellas.
Bye, everybody.
See you, Nate.
Thank you.
Bye.
As for the rest of us, let's come back to Earth with our new water molecule friends.
Let's make it rain.
Are you ready?
Here we go.
LAUGHTER
So Edward, dew forms when water in the air collects on the ground.
The air is full of lots of different molecules.
Nitrogen, oxygen, carbon dioxide.
And water molecules swirling all around us as an invisible gas.
You can't see it.
When it's warm, the air molecules bounce around with lots of energy and keep the water molecules apart.
When things cool down, they slow down and the air molecules can't keep the water molecules apart anymore.
When this happens, the water condenses on the ground as dew.
The grass will be wet and dewy when it's cooler, like in the early morning.
And then it disappears when the sun rises and heats things up.
It evaporates.
Water molecules then head up into the air, where they hang around until they're blown away or condensed in the sky.
Clouds.
Until the droplets get so big that they fall down again as rain.
And the cycle starts again.
