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Welcome to the Bedtime 
scientist. 

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Tonight we aren't going to 
travel down to the bottom of the

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sea. 
We're not even going to leave 

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the spot where you're resting 
right now. 

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Tonight, all we have to do is 
look up, because there's 

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something that drifts over your 
head almost every day, something

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you've seen 1000 times that 
turns out to be far stranger and

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far heavier than it looks. 
Take a deep breath in, let it 

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out, close your eyes and imagine
with me. 

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It's the end of the day and 
you've gone outside to lie back 

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in the cool grass, nowhere to 
be, nothing to do but look up 

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and let your mind wander. 
The air has started to cool. 

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Somewhere nearby a cricket is 
making its small evening sound, 

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and above you is the sky, wide 
open. 

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At first it might look like 
there's nothing there, but then 

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you notice them. 
Clouds. 

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Some are long and thin, like 
pale brush strokes. 

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Some are wide and rounded right 
along the top edge 1 is so big 

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it seems to move like a slow 
ship crossing an invisible sea. 

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From down here, a cloud looks 
soft, light, like it's drifting 

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along without any effort at all.
A cloud is made of water. 

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Not puddles, not raindrops you 
could catch in your hand. 

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Tiny droplets so small you could
never hold just one, so light on

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their own that the air keeps 
them floating. 

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They form around something even 
smaller. 

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A speck of dust. 
A grain of salt lifted off the 

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ocean. 
A bit of pollen from a flower. 

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Water gathers around the tiny 
speck and a droplet begins. 

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Then another. 
Then another. 

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Millions of them. 
Sometimes billions. 

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And when scientists carefully 
weigh one of those big puffy 

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white clouds, the kind that 
drifts across the sky on a 

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summer afternoon, they find 
something hard to believe. 

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It can weigh £1,000,000, a 
million pounds heavier than a 

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long line of elephants, heavier 
than a row of trucks parked end 

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to end. 
But there it is, floating 

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quietly over your head. 
So how does something that heavy

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stay up? 
The weight is spread out. 

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The water in a cloud isn't 
gathered into one heavy bucket. 

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It's scattered into those 
countless tiny droplets drifting

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through an enormous stretch of 
air, and the air is moving. 

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Warm air rises up from the 
ground all the time, and that 

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slow rising is enough to hold 
each tiny droplet up. 

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So the cloud is heavy and the 
cloud floats. 

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Both of those are true at the 
very same time. 

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From far away, a cloud looks 
like one simple thing, white and

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plain, easy to Passover. 
But inside it, there are more 

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droplets than you could ever 
count. 

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Inside it, there's motion. 
Inside it there's weight. 

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A whole hidden world, all held 
together in one soft shape, 

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drifting along like it weighs 
nothing. 

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The water inside it has been 
somewhere before too. 

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The water in a cloud above you 
tonight might once have been 

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deep in the ocean where no 
sunlight could reach. 

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Before that rain on a forest, 
and before that, frozen still 

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inside a mountain glacier. 
Long before anyone alive today 

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was born. 
And now here it is again, lifted

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back into the sky, gathered into
something bright and floating. 

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A cloud doesn't hold on forever,
though. 

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As more water gathers, the 
droplets grow. 

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They bump into each other and 
join and grow heavier and 

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heavier, and there comes a point
and the rising air can't hold 

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them up any longer. 
So the cloud does the next 

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thing. 
Clouds do. 

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It lets go. 
The rain begins. 

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Not because anything went wrong,
not because the cloud failed. 

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The cloud carried what it could 
for as long as it could, and 

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then the time came, and letting 
go was simply the next part. 

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And what it lets go of isn't 
lost. 

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It soaks into the ground and 
feeds what grows there. 

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Even the letting go turns into 
something the world needs. 

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So picture 1. 
Cloud now, drifting slowly above

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you, not rushing anywhere, not 
trying to be any other shape, 

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just moving along with the air, 
holding what it holds, and when 

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the time comes, letting some of 
it go. 

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The sky knows how to carry it, 
the earth knows how to catch it,

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and everything keeps moving. 
You carried a lot today too. 

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Some of it was light and some of
it was heavy. 

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A hard moment, a worry that 
stayed a while, a feeling too 

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big to find the words for. 
All of it real, even the parts 

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no one else could see from the 
outside. 

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You don't have to keep holding 
it now. 

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You can set it down. 
You can let it move on through 

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the way rain moves on through 
the soil into something quieter.

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Setting it down isn't failing, 
it's just the next part. 

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You can let something else do 
the holding for a while, and you

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don't have to remember any of 
how clouds work. 

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Not the speck, not the 
£1,000,000. 

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You can let all of it drift off 
too. 

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It'll still be true in the 
morning, so let yourself grow 

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heavy, let the day grow quiet, 
and let your mind drift back up 

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to that wide open sky the way it
did in the grass, with nowhere 

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to be and nothing to carry, just
watching the clouds go by. 

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And just before you drift off to
dream of clouds drifting slowly 

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overhead, tiny droplets too 
small to see, and all the water 

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that has traveled the whole 
world just to float above you. 

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Tonight, I want you to know 
something about you. 

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Your mind is a wonderful thing, 
so full of curiosity, and I like

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your mind just the way it 
wonders. 

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I'll be back again soon to 
wonder more with you.