Pictures: First Quadruple Rainbow Ever Caught on Camera

First Triple Rainbow Picture

Diagram courtesy Michael Grossmann, Applied Optics

The first picture of a tertiary rainbow was taken in Kampfelbach, Germany, on May 15, 2011, and required heavy image processing (right) to reveal the third arc. (The other two are behind the photographer and visible only when facing away from the sun.)

"It's not a bright rainbow. It's more a very subtle change in color," study co-author Philip Laven said of tertiary rainbows. "It's very difficult [to see]—everything has got to be just right."

(Download rainbow wallpapers.)

Published October 7, 2011

Double Rainbow Over Alaska

Photograph by Rich Reid, National Geographic

Rainbows, including this double rainbow over Alaska, form when sunlight is refracted, or bent, inside a raindrop, reflected by the drop, and then refracted again as it exits, so that the white light is split into its component colors. A double rainbow appears when light is reflected twice. A triple rainbow would come from thrice-reflected light, and so on.

"It's counterintuitive" to most people that the triple rainbow would be near the sun, Lee said. "People have this reasonable expectation that, I see something pretty in that direction, so all the pretty things would be in that direction.

"But there's nothing weird going on here. Just as a mirror can send light in many different directions, so can raindrops."

(Pictures: "Night Shining" Clouds Getting Brighter.")

Published October 7, 2011

Colorado Colors

Photograph by Robbie George, National Geographic

Rainbows across a dramatic backdrop, such as this Colorado landscape, may look gargantuan, but they're actually the same "size" as rainbows created when light hits the spray from a garden hose, Lee said. Those garden-hose rainbows are really just small segments of full rainbow arcs that, given the right conditions, would extend as far as the ones pictured.

"But people associate the image with whatever they see on the landscape, so the ones you see against the beautiful background" are more emotionally stirring.

In other words, rainbows are visions, but only illusions. "People get very excited by seeing a bright double rainbow, and they just project onto it their own emotions," Lee said.

"Just last weekend at the grocery store," added Lee, "I saw one of the finest double rainbows it was my luck to see in 20 years."

(Related: See a new species of "rainbow glow" jellyfish.)

Published October 7, 2011

Island Arcs

Photograph by Kenneth Garrett, National Geographic

Seen from the sky, a double rainbow seems to touch down on reefs off the Yucatán Peninsula (map).

For years rainbows have fascinated thinkers, including 17th-century French philosopher and optics scholar René Descartes, of "I think, therefore I am" fame. Descartes, a rainbow expert, was wrong about triple rainbows, though. He proclaimed that viewers should be able to see stacks of three rainbows.

"One of the fathers of rainbow science," Lee said, "got it wrong."

More: See a flame-like "rainbow" over Idaho >>

Published October 7, 2011