The multi-coloured shimmer given off by fish skin is called iridescence, and it’s pretty fascinating.
You’ve seen iridescence before: in patches of oil on the ground, butterfly wings, peacock feathers. It’s one of those commonplace natural occurrences that doesn’t often get the reverence it deserves because…well, because it’s so commonplace.
It all stems from the scientifically baffling way that light behaves.
Now, my background in quantum mechanics is approximately zero. But the idea is that light behaves like a wave when it feels like it, and like a particle when it feels like it. Or sometimes, when light is feeling particularly frisky, it behaves like both.
Anyway, the beautiful reflective rainbow effect that we know as iridescence happens because some materials (oil, seashells, etc.) reflect coloured light at angles which make the light waves interfere with each other, at times amplifying each other, and at times cancelling each other out. If you’d like someone to explain it better, and more visually, take a quick break to watch this video.
Okay, so some materials are iridescent. That’s cool.
But what makes fish skin doubly cool is that the crystals in fish skin responsible for refracting light don’t grow the way crystals are supposed to grow. Crystals, according to the rules, grow as prisms. But ten years ago, a group of scientists found that somehow, fish manage to get their skin crystals to grown in thin plates instead of prisms, giving them their iridescent magic.
How is it that fish are able to tell their crystals to grow differently? Nobody knows. I’ve always thought that most fish, with their big dopey eyes and gaping mouths, look a little too dumb to be able to outsmart crystals.
If any fish are reading this, please accept this beautiful song as my sincere apology for underestimating you.
What makes this a beautiful song:
1. The main keyboard line, on two simple intervals, repeating like flapping fish fins.
2. Between each repetition of that keyboard line, the descending high notes, like an iridescent shimmer as the fish goes by.
3. The soft saxophone, sighing like an awestruck observer (aka me) watching in wonder.
Recommended listening activity:
Trying to catch a soap bubble on the end of your finger.