Eddie Wu

The shape of a rainbow is not just half of a circle.

It is actually a full circle, and that circle is the shape of the rainbow that you and I see.

It's just that we usually only see half of it because the horizon is blocking its path.

so i actually was very recently up in a plane you can see that actually the shape of a rainbow is not just you know sort of half of a circle it is actually a full circle and what is happening here is one of these most phenomenal ideas that i've ever experienced which is that i want you to picture mike uh the rain has just been falling for the last couple of hours but suddenly it's it's stopped the clouds are starting to part

And the sun is beginning to shine again.

All right, what is happening in this moment?

Well, firstly, even though the rain has stopped, there is actually still a lot of water in the air.

All of these hundreds of millions of droplets kind of still suspended in the atmosphere.

And each one of those individually acts like a little prism and a little mirror that reflects light from the sun around Earth.

all of the different directions.

So every one of those hundreds of millions of raindrops in the air is doing that.

It's refracting the light into its different component colors.

But a raindrop is not a triangular shape.

It's round.

And so what will happen is that light will refract

but it will rebound on the inside of that roughly spherical raindrop and it will go back, it will reflect back in the direction roughly that it came from.

Now, there are some of those raindrops in the air out of those countless number that will reflect back to your eyes and to mine that particular spectrum and all of those particular raindrops

are going to be in the shape of a cone.

Now, if you look at a cone from the top, you don't see the whole sort of, you know, ice cream cone shape.

You actually see the cross section of a cone, which is a circle.