You look up after a storm, and there it is — a giant glowing arc stretched across the sky, impossibly bright, impossibly perfect. Where did all those colors come from?

The answer starts with something invisible: white sunlight isn't really white. It's actually a mix of every color of light smooshed together — red, orange, yellow, green, blue, violet, all traveling in one beam. Your eyes can't tell them apart when they're bundled up like that, so you just see "white."

Now imagine a raindrop hanging in the air — a perfect tiny sphere of water. When that white sunlight hits the raindrop, something strange happens: the raindrop bends the light as it enters. And here's the key part: it bends each color by a slightly different amount. Red bends the least. Violet bends the most.

The light travels through the raindrop, hits the back wall, and bounces. Then it exits the front again — still split into its separate colors. What entered as one white beam leaves as a tiny rainbow spray. Every raindrop in the sky is doing this, all at once, sending colored light in every direction.

But here's why you see a rainbow and not just a random spray of colors: geometry. You only see the color from a raindrop if it's at exactly the right angle between you, the drop, and the sun. For red light, that angle is about 42 degrees. For violet, it's about 40 degrees.

So when you look up, you're actually seeing red light from raindrops high in the sky at that 42-degree angle, orange from drops slightly lower, yellow lower still — all the way down to violet from drops at 40 degrees. Millions of raindrops, each one sending you one color from one spot. Together, they paint the arc.

That's why a rainbow is always the same shape, the same order of colors, and always appears opposite the sun. You need sun behind you, rain in front of you, and exactly the right angle. Move ten feet to the left, and you're seeing a completely different set of raindrops — a new rainbow, just for you.

And when the rain clears and the drops vanish? The rainbow vanishes too. It was never a thing you could walk to or touch — just millions of tiny prisms, catching light for a moment, bending it your way, then disappearing into the air.