Full-Circle Rainbow

If you could get up high enough in the sky, then you'd see that some rainbows continue below the horizon. That's because when the sun and rain combine to make a rainbow, they really make a full-circle rainbow. We can't see all of the circle, because the horizon blocks it from our view. Pilots high in the sky do sometimes report seeing genuine full-circle rainbows.

The only way to see the full circle of a rainbow in the sky is to be above the raindrops and have the sun behind you.