Nimbus and the Volcano Rainbow

This is Nimbus, a small cloud who wants to be a real scientist. Her story happened on a volcano island way out in the ocean, where the volcano was asleep but still warm, like a cake that just came out of the oven. Nimbus floated all the way there because she had a hypothesis: the volcano was the reason there were always rainbows over the island, and she wanted to prove it with a proper experiment.

Nimbus put on her safety goggles and floated carefully down into the crater. Inside, it was warm and dark and steamy, with little puffs of steam whistling out of cracks in the rock. She wrote on her clipboard, "Observation one, the volcano is breathing." But then something strange happened. Her clipboard started to feel heavy, and she noticed she was getting bigger and bigger and puffier. She couldn't figure out why.

When Nimbus floated out of the crater, she was enormous now, the biggest she had ever been. A whole family of seabirds landed on her, thinking she was a comfy island. The oldest seabird told her that every afternoon a rainbow appeared over the volcano, but nobody knew where it came from. The birds had a legend that the volcano was painting it.

Nimbus said very politely that legends are lovely, but a scientist needs evidence. The birds all ruffled their feathers because nobody had ever argued with the legend before. She remembered from a book that a rainbow is made when sunlight goes through water drops and gets split into all its colors, so she thought maybe the volcano's steam was making the rainbow. To test it, she had to wait for the afternoon sun and be in exactly the right place.

When the afternoon sun came out, Nimbus floated to the side of the volcano where the biggest steam crack was. She concentrated really hard and rained exactly one drop at a time into the sunlight. And there it was, a tiny rainbow hanging in the air right next to her! Then the steam from the crack drifted up into the sun, and the tiny rainbow stretched and stretched until it went all the way over the island. The birds went completely silent and then all started squawking at once.

The birds were saying the legend was almost right; the volcano was making the rainbow, just not by painting it. The oldest seabird said he had watched that rainbow every day for thirty years and never once thought to ask why. Nimbus turned bright pink like a sunset because she was proud. She wrote on her clipboard, "Conclusion, the volcano's steam plus the afternoon sun equals a rainbow, hypothesis confirmed." The oldest seabird asked if he could be her assistant, and she said yes.

That evening, Nimbus floated home a little smaller because she had rained some of herself out. She looked back, and the rainbow was still there over the volcano. And now she knew exactly why.