You blow a bubble, and there it goes — floating, wobbling, and somehow wearing a swirling rainbow coat it didn't have a second ago. The soap film is clear. The air is clear. So where do all those colors come from?

Here's the trick: a soap bubble isn't one layer — it's a sandwich. There's a super-thin layer of soapy water trapped between two layers of soap molecules. When sunlight hits that sandwich, something strange happens to the light on its way through.

White light — the kind that comes from the sun — is actually made of all the rainbow colors traveling together as waves. Red light has long, lazy waves. Blue light has short, zippy waves. They all move at different speeds through the soap film.

Now watch what happens. Some light waves bounce off the bubble's outer surface and head back toward your eyes. But some slip through the film, bounce off the inner surface, and then come back out. So you get two sets of waves leaving the bubble — and they've traveled different distances.

Here's where it gets wild. When those two sets of waves meet up again in the air, they either high-five each other or cancel each other out — depending on whether their peaks and valleys line up. If a red wave's peaks match up, you see red. If they're mismatched, the red disappears.

The soap film is so thin that different colors match up in different spots. Where the film is one thickness, red waves high-five and you see red. A hair's width away, where it's slightly thicker, blue waves high-five instead. The film's thickness changes constantly as the bubble wobbles and drains.

That's why the colors swirl and shift as you watch. Gravity pulls the soapy water downward, making the top thinner and the bottom thicker. The wind nudges the film around. Every wobble changes which color's waves are lining up perfectly — so the rainbow never sits still.

Right before a bubble pops, the top gets so thin that no colors line up anymore — the film turns clear or even black. And then, in a blink, the whole rainbow vanishes. But don't worry. There's always another bottle of soap, another breath, another wobbling rainbow waiting to happen.