Do you remember how rainbows form?

There's a ton of videos out there that explain them.

The physics is pretty easy.

Light enters tiny water droplets, bends or refracts, bounces, bends again, and different colors end up in your eye.

Easy, right?

But if you've ever looked up in the sky and seen a bright halo around the sun, or the moon, or a fiery explosion of colors, that's not a rainbow.

It's way cooler.

In fact, you might even say it's ice cold.

In an old video, we talked about the science of snowflakes and how the shape of H2O gives frozen water crystals a six-sided symmetry all the way down to the atomic level.

But way up in the atmosphere where it's cold and dry, instead of forming the snowflakes that you know from ugly Christmas sweaters, ice crystals end up more like this.

These crystals can act like tiny sun-bending prisms.

And if they end up between you and the sun, like inside a Cirrus cloud, they can form those amazing halos.

So how does it happen?

Inside that cloud, there's prisms arranged in all different directions.

If we zoom in on a slice like this, crystals in different positions will be rotated in just the right way so that the light coming out the other side will be bent towards your eye.

Different rotations refract light at different angles.

But since those angles average about 22 degrees, the halo is brightest right there.

And since no light is bent at less than 21.7 degrees, we see a dark hole in the center.

When the sun is even lower in the sky, much cooler things can happen.

How cool?

I'm trying to think of a pun here, but I seem to be freezing up.

Sorry.

Instead of prisms, some ice crystals end up like six-sided Frisbees.

And just like autumn leaves, they tend to fall with their flat sides down because of air resistance.

This means that close to the horizon, those crystals are oriented the same way, which creates more concentrated refraction in very specific spots.

It can look like there's three suns.

And because these fake suns obediently follow their solar master through the low sky, we call them sundogs.

You know how in a rainbow, longer wavelengths are bent slightly less?

Well, that happens here too, tinting the inside of a sundog slightly red and the outside slightly blue.

On rare occasions, you can see this.

A ring stretching around the entire sky.

Instead of refraction, those flat ice crystals are reflecting like mirrors.

This stuff can even happen around the moon.

These are just a few of the amazing things that can happen when light meets ice.

When those conditions are just right, it can look like Bob Ross went nuts and dragged his icy paintbrush all over the sky.

Between clouds, sunsets, rainbows, and now all this icy awesomeness, it can be hard to pick a favorite atmospheric phenomenon.

Luckily, you don't have to.

Enjoy them all.

And keep looking up, just not directly at the sun.

Stay curious.