Yes, that really is a rare twin rainbow in the image above where two colorful arcs spring from the same starting point. You’ve probably seen the viral video, but have never seen one in real life. They are extremely rare. Now researchers from the University of California, San Diego, have used a 3D computer model to figure out how these twin rainbows form.
It’s all about raindrops, their shape, and how they scatter light. The pair splits apart when light is filtered through two different types. Small, round drops push light in one direction while larger drops, which flatten on the bottom as they fall through the air, push light in a different direction.
The researchers call the larger drops “burgeroids” because their shape looks like a hamburger without the bun. Using “burgeroids,” they can accurately replicate the double rainbow phenomenon. No matter how you explain it, it is a beautiful sight.