Why Is Snow White When Ice Is Clear?
Even though it wasn’t super hot today, I still had a craving for ice cream. So, Mika and I went to our favorite café for a big scoop of stracciatella! We were just sitting down when the sky suddenly turned dark, and a summer thunderstorm surprised us. We quickly huddled under the big café awning as it started to rain and even hail!
I picked up one of the little hailstones from the ground. It was like a tiny, clear ball of glass. Admiring its cold beauty, I remembered a question that had been bugging me since winter. “Mika,” I whispered, “why is this hailstone clear, but snow is white? They’re both just frozen water, right?” Just then, a friendly voice said, “That’s a fantastic question!” We looked up and saw a man sitting at the next table, who introduced himself as Josh. He told us he was a scientist and would be happy to explain the mystery.
Josh explained that it all has to do with sunlight. Sunlight looks white, but it’s actually made of all the colors of the rainbow mixed together. A clear hailstone or an icicle is like a smooth window. The light can pass straight through it, so it looks clear to us. But snow, he said, is completely different. It’s not one solid block of ice. It consists of millions of tiny, clear ice crystals all jumbled together, looking in random directions with lots of air trapped in between. When sunlight hits the snow, it’s like the light gets lost in a maze! It bounces from one tiny crystal to the next, scattering in every direction. Because none of the colors gets trapped, the whole rainbow of light bounces right back out at our eyes. And when our brain sees all the colors at once, it just says, “That’s white!”
Then Josh told us the coolest thing: this trick works for other things, too! He said a polar bear’s fur isn’t actually white. Each hair is a clear, hollow tube. Just like with snow, light bounces around inside all the hairs and comes back out looking white. And underneath all that “white” fur, a polar bear’s skin is actually black! Just as he finished explaining, the rain stopped and the sun came out. It’s funny how a sudden summer storm and a scoop of ice cream can help you solve a winter mystery.
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Text: Joshua Müller, Illustration: Patrizia Schoch