# Sister, Sister, Why is the Sky So Blue? - Source: StoryWeaver (storyweaver.org.in), CC BY, Pratham Books, StoryWeaver, CC BY 4.0 - Reading level: Grades 3 and 4 - Subjects: Science, Weather - Topics: blue, think, little, sister, brother, light - Length: 1032 words, about 7 min - By: Roopa Pai - Original: - Page: - Open in Sprouts: Sister, sister, I wonder… What do you wonder, little brother, What do you wonder? I wonder, I wonder, why the sky is so blue. What do you think, little brother, What do you think? I think, I think… Tell me, little brother, what do you think? I think That maybe the sky Is really an upside-down sea With cloud-boats bobbing gently along. That an E-NOR-MOUS sheet Of clear plastic skin Is stretched across that upside-down sea To keep it in. And sometimes the plastic tears a little Here or there Like plastic will And then it rains. I think that is why the sky is blue Because it is a sea And seas are blue. I’m clever, aren’t I, sister? Oh yes you are, little brother, oh yes you are And maybe you are right, too... But in the books I have read That is not what they said. Then what did they say, sister, what did they say? What do you think, little brother, what do you think? I think, I think, Tell me, little brother, what do you think? I think That maybe the old woman Who lives in the sky Washes her ENORMOUS blue saree each night And spreads it out to dry in the sun Each morning. She is careful, the old woman She pins the saree down with cloud-stones So that the naughty wind Cannot carry it away. I think that is why the sky is blue Because the old woman in the sky Spreads her saree out to dry. I’m clever, aren’t I, sister? Of course you are, little brother, And maybe you are right, too… But in the books that I have read That is not what they said. Then what did they say, sister, What did they say? What do you think, little brother, what do you think? I think, I think… Tell me, little brother, What do you think? I think That maybe, one long-ago Holi The shops ran out of every colour BUT blue. And I think, that day, Such an ENORMOUS cloud of blue dust rose From laughing blue people everywhere, That it reached up, up, up all the way To the sky. And the old woman, the one that lives up there, She scrubs the sky each day With cloud-cottonwool, To get the stain out of the way. I think that’s why the sky is blue Because of a stubborn stain That drives the old woman insane. I’m clever, aren’t I, sister? Oh yes, you are, little brother, oh yes you are And maybe you are right, too… But in the books I have read That is not what they said. Then what did they say, sister, What did they say? What do you think, little brother, What do you think? They said, they said… Tell me, sister, what did they say? They said That there is a thick blanket of air Around our blue and green earth And that blanket is woven Of millions of little things they call Mo-le-cules. They said The air blanket is called At-mos-phere. But why is the sky so blue, sister, Why is the sky so blue? Be patient, little brother, be patient now. They said The golden light from the glorious sun Is not golden at all But white! And what a white! A rainbow-coloured white! A violet-indigo-blue-green-yellow-orange-red white. They said It is the RAINBOW light That comes to us Through the At-mos-phere. But the sky is blue, sister, not violet or yellow or green! Listen, little brother, you'll see what I mean. Now the Mo-le-cules in the At-mos-phere Well, they are not very fair. They let the red and the yellow and the orange light pass through Mostly And the green too But the blue! Oh, they give the blue a hard time! What do they do to the blue, sister, What do they do? Tell me, sister, what do they do? Well, when the sunlight strikes those Millions and millions of MO-le-cules They BOUNCE all that blue light The blue, blue light's Back where it came from; And the poor blue light Shatters, scatters All over, ALL OVER, the sky And turns it blue. Can it be true, sister, can it be true? I can’t say, little brother, I can’t say. But in all the books that I have read That is what they said. FIND OUT MORE! **Why is the sky blue?** Sunlight is made up of all the colors of the rainbow: red, orange, yellow, green, blue, indigo and violet. The gas molecules in the atmosphere interact with the sunlight before it reaches our eyes. Each ‘colour’ of light is actually a different wavelength of electromagnetic radiation. Different wavelengths not only make up different colours, they also behave differently. Each of the different wavelengths in sunlight (or, in other words, each of the colours that sunlight is made up of) interacts differently with the molecules in the atmosphere. When sunlight strikes the molecules, they scatter the blue light (which has a shorter wavelength) more than they do the red, orange, yellow and green lights (which have longer wavelengths). Since the blue portion is scattered more, the sky appears blue. **Try this experiment!** Why does the sky appear orange and red at dawn and dusk? Let's try this exercise to find out. **You need:** A clear glass full of water A little milk A torch **What to do:** Shine the torch on the glass of water. Can you see the light in the water? Hardly. Now add a few drops of milk into the water. Then shine the torch again on the glass. This time, you will notice that the light is more visible. Add a few more drops of milk. Now you will notice that the light in the glass is distinctly blue. **Why does this happen?** When you add the first few drops of milk to the water, the number of molecules in the water increases. The fat and protein molecules in the milk scatter the light so that we can see it. When you increase the number of molecules by adding more milk, the light is scattered more, especially the blue light, which has a shorter wavelength. ## Picture credits - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 () - Greystroke, CC BY 4.0 ()