Mingo’s Big Question

Mingo was lying on his back in the grass, looking up at the sky. “Why is the sky blue?” he wondered out loud. “Why isn’t it green, like the grass? Or yellow, like the sun?” Nobody in the Meadow knew the answer. Mingo sprang to his feet and straightened his glasses. “Then we’ll find out!”

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Mingo gathered his friends, and Nini, Dali and Zana came straight away. Bleta came too. “What a lovely question!” she said. “Shall we look for clues together? Just remember: never look straight at the sun, because it can hurt your eyes.” Mingo took out his magnifying glass. “Explorer team, let’s go!”

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The first clue came from Nini. On a blade of grass, a drop of dew was sparkling. “Look!” she cried. “There are tiny colours inside!” Mingo bent down with his magnifying glass: red, orange, yellow, green, blue, violet. “A tiny rainbow inside a drop of water!” he gasped.

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The second clue came from Dali. He put a glass of water in the sunshine, next to a white sheet of paper. Slowly, a stripe of colours appeared on the paper, like a little rainbow. “Sunlight looks white,” said Dali, “but all the colours are hiding inside it! When it passes through water, the colours come apart.”

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Mingo wrote everything down in his notebook. “So sunlight is all the colours mixed together. But then why do we only see blue up there?” He pointed his magnifying glass at the air, but saw nothing at all. “The air is full of tiny bits,” Bleta told him, “so tiny that you can’t see them, not even with your magnifying glass.”

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“When sunlight travels through the air, it bumps into those tiny bits,” Bleta explained. “Red and orange light carry on almost straight ahead. But blue light bounces about much more, this way and that, in every direction! So blue light reaches our eyes from every part of the sky. That’s why the whole sky looks blue.”

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That evening, everyone sat together on the hill. The sun was setting, and the sky turned orange, pink and red. Suddenly, Zana’s light flicked on. “I’ve got an idea!” she said. “In the evening the sun is very low. So its light has to travel a much longer way through the air to reach us.”

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“I get it!” cried Mingo happily. “On that long journey, the blue light bounces off to the sides before it ever gets to us. What reaches our eyes is mostly the red and orange light!” Bleta smiled. “Exactly. That’s how a real explorer team works.”

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That night, Mingo wrote in his notebook: “The sky is blue because the air scatters blue light in every direction.” Then he added: “I found the answer, but not on my own. Nini found the dewdrop, Dali the rainbow, Bleta the tiny bits of air, Zana the sunset. A big question needs lots of eyes!” Then he looked up from his notebook. “Hmm… and why is grass green?”

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