Here’s How Rainbows Really Form

If you’ve ever spotted a rainbow stretching across the sky, then you’ve witnessed a little bit of science and a little bit of magic, perfectly timed.

According to meteorologist Sara Tonks, rainbows can be rare because they require a very precise setup: rain in front of you, sunlight behind you and the sun sitting at just the right angle.

Now, the sunlight we see normally may look bright white, but it’s actually made up of every color in the spectrum, often remembered as ROYGBIV: red, orange, yellow, green, blue, indigo, violet.

When that light enters a raindrop, the droplet acts like a tiny prism. The light bends, splitting into all those individual colors.

When the correct ingredients are in place, raindrops will reflect all of those colors back to you, which is when you see a rainbow.

That's an important distinction many people miss: You’re not really “seeing” the raindrops themselves. You’re seeing sunlight bouncing off of them.

(MORE: Why You’ll Never Find The End Of A Rainbow)

Without the sun positioned behind you, that light would just pass straight through the raindrops and continue on its way, no rainbow at all.

ROYGBIV

The order of colors in a rainbow is no accident, either.

Each color has a different wavelength, and when light splits, those wavelengths separate in a consistent pattern. Violet, with the shortest wavelength, appears on the inside of the arc, while red, with the longest wavelength, stretches across the outer edge.

What makes one rainbow faint and another incredibly vivid?

It all comes down to the number of water droplets in the air. Each droplet contributes a tiny piece of the rainbow, so the more droplets there are, the brighter and fuller the display becomes.

Sometimes, you might get lucky and spot a double rainbow. That happens when light reflects twice inside the raindrop instead of once.

(MORE: Vivid Double Rainbow Spotted In Bay Area)

The result? A second, fainter arc above the first, with its colors reversed. It’s essentially a mirror effect created by that extra internal bounce.

Another fact that might blow your mind: Rainbows aren’t just arcs, they’re actually full circles.

(MORE: Skydivers Capture Full Rainbow)

The reason you only see part of one is simple: The Earth gets in the way.

From the ground, the horizon blocks the lower half. But from high altitudes, like in an airplane, people can sometimes catch a glimpse of a full circular rainbow.

Rainbows aren’t limited to rainy skies, either. Anywhere you have tiny water droplets suspended in the air, you can get one.

Mist from a waterfall, ocean spray or even fog can produce rainbows. These often look softer or less defined because the droplets are smaller, causing the colors to blur together slightly.

In the end, rainbows are a fleeting phenomenon, which is part of what makes them so special. You can’t touch one, you can’t reach its “end” and you’ll never see the exact same rainbow as someone standing a few feet away.

They’re not just weather and light, but pieces coming together to make magic.