A child studies their own shadow the way toddlers study everything, noticing it copies every jump but refuses to play properly, growing tall then shrinking to nothing. It rewards a sunny window or a torch held low on the wall, so the shadow it describes can be pointed at while you read.
From A Child's Garden of Verses. See the whole collection.
I have a little shadow that goes in and out with me,
And what can be the use of him is more than I can see.
He is very, very like me from the heels up to the head;
And I see him jump before me, when I jump into my bed.
The funniest thing about him is the way he likes to grow—
Not at all like proper children, which is always very slow;
For he sometimes shoots up taller like an india-rubber ball,
And he sometimes gets so little that there's none of him at all.
He hasn't got a notion of how children ought to play,
And can only make a fool of me in every sort of way.
He stays so close beside me, he's a coward you can see;
I'd think shame to stick to nursie as that shadow sticks to me!
One morning, very early, before the sun was up,
I rose and found the shining dew on every buttercup;
But my lazy little shadow, like an arrant sleepy-head,
Had stayed at home behind me and was fast asleep in bed.
About this poem
Robert Louis Stevenson · From A Child's Garden of Verses, 1885
Also Robert Louis Stevenson, from his 1885 book A Child's Garden of Verses, and one of the best-known poems in it. The whole poem is a child honestly puzzling over his own shadow: the way it shoots up tall or shrinks to nothing, how it sticks close all day, then one morning stays behind in bed, 'an arrant sleepy-head', because the sun is not yet up to cast it. Stevenson remembers exactly how a small child reasons.
This one wants to be read near a light. On a sunny walk, or with a torch on the bedroom wall, find your shadows and watch them stretch and shrink. Jump, and let them jump. A child who has never looked properly at a shadow tends to start after this. Early morning, when yours runs long, is a good time.
Public domain. Text from A Child's Garden of Verses (Robert Louis Stevenson, 1885), via Project Gutenberg. View the source edition