Buzz
While we know triple rainbows are incredibly rare, what makes it so difficult to observe this weather phenomenon? Anthony DeLorenzo via Wikimedia CommonsKey Insights
- Triple rainbows are extremely rare atmospheric events.
- They occur when sunlight is reflected multiple times within raindrops.
- These rainbows display three separate color arcs, with the outermost one being the faintest.
Charles Montgomery Burns (better known as the villainous Mr. Burns from TV’s "The Simpsons") poses a similar question in his autobiography "Will There Ever Be a Rainbow?" We’ll try to answer it – and unlike Mr. Burns, we won’t be relying on a ghostwriter.
Unlike the more common rainbows and even double rainbows (sorry, awe-inspired YouTubers, but they occur fairly often), triple rainbows are far from ordinary. In fact, they’re so rare that before a 2011 photograph we’ll discuss later, only five triple rainbows had been verified in 250 years [source: Byrd].
Let’s go over a quick explanation of how rainbows form. When light (in this case, sunlight) enters a raindrop, it reflects once off the back of the drop and then bends again as it exits [source: Mass]. This results in a single rainbow being visible.
When light is reflected twice within a raindrop, you get a double rainbow [source: Byrd]. As mentioned earlier, double rainbows aren’t that uncommon, as it’s not unusual for light to come from different angles.
Triple rainbows, however, are a completely different story. The same principle applies – the light must reflect inside the drop three times – but this is a lot trickier. There are specific conditions needed for the light and atmosphere to be just right. According to Raymond Lee, a meteorology professor at the U.S. Naval Academy, these include dark clouds and uniformly sized raindrops [source: Geere].
Here’s the key difference between triple and double rainbows. In a triple rainbow, the third reflection is only visible on the opposite side of the sky. This means that the third arc appears behind you, where the sun is visible – not ideal for spotting a rainbow. Additionally, each reflection dims, making the third arc very faint [source: Geere].
Returning to that famous image from 2011. After discussing the ideal conditions for triple rainbows, some people became eager to try and capture one. Photographer Michael Grossman managed to get incredible shots of a triple rainbow in 2011, and that same year, meteorologist Michael Theusner published a paper that referenced evidence of him capturing a quaternary rainbow [source: Theusner].
What’s the takeaway here? If you really want to amaze the Internet, upload a video of yourself freaking out over a quadruple rainbow.
