“Many of us know that triple rainbows are very rare, but why is it so hard to find the weather phenomenon?Anthony DeLorenzo via Wikimedia Commons
Charles Montgomery Burns (aka the evil Mr. Burns from TV’s "The Simpsons") asks a similarly plaintive question in his autobiography "Will There Ever Be a Rainbow?" We’ll do our best to answer it – and unlike Mr. Burns we won’t use a ghostwriter.
Unlike ho-hum rainbows and even double rainbows (sorry, awe-inspired YouTubers, but they happen quite a bit), triple rainbows are not your run-of-the-mill weather phenomenon. In fact, they’re so rare that prior to a 2011 image that we’ll talk about later there had only been five verified reports of triple rainbows in 250 years [source: Byrd].
Let’s get a quick tutorial in how rainbows work. When light (in this case, sunlight) enters a raindrop, it reflects once off the back of the drop, and then bends again as it leaves the drop [source: Mass]. This is when you see a single rainbow.
If light is reflected twice in the drop of water, you’re going to get yourself a double rainbow [source: Byrd]. As we said earlier, double rainbows are not so unusual, because it’s not that rare to have light coming from a couple of different angles.
But it’s a way different story when it comes to triple rainbows. Technically the same idea applies – the water must reflect the light three times. Yet this is not so easy. There are specific conditions necessary to get the right light and atmosphere. According to Raymond Lee, a professor of meteorology at the U.S. Naval Academy, they include dark clouds and a shower of uniformly sized drops [source: Geere].
Here’s the big difference between triple rainbows and double rainbows. With a triple rainbow, the third reflection is actually only visible in the opposite part of the sky. That also means the third arc of a triple rainbow is behind you, in the part of the sky where the sun is visible – not exactly the greatest conditions for spotting a rainbow. Adding to the trouble is that each reflection of the rainbow gets dimmer, so you see only a very light third arc [source: Geere].
Back to that picture that surfaced in 2011. After talk about the ideal conditions for triple rainbows, a few people got interested in trying to record some. Photographer Michael Grossman got some extraordinary photography of a triple rainbow in 2011 and, that same year, meteorologist Michael Theusner published a paper citing evidence that he captured a quaternary rainbow [source: Theusner].
The lesson here? If you really want to impress the Internet, post a video of yourself losing it over a quadruple rainbow.
Lots More Information
- How Rainbows Work
- How Light Works
- Can we control the weather?
- Byrd, Deborah. "First-ever photos of triple and quadruple rainbows." EarthSky. Oct. 9, 2011. (Dec. 16, 2014) http://earthsky.org/earth/first-ever-photos-of-triple-and-quadruple-rainbows
- Ehrlich, Brenna. "Double Rainbow Meme Takes Web by Storm [Randomly Viral]." Mashable. July 8, 2010. (Feb. 2, 2015)http://mashable.com/2010/07/08/double-rainbow/
- Geere, Duncan. "Meteorologists track down elusive triple and quadruple rainbows." Wired. Oct. 6, 2011. (Dec. 16, 2014)
- Geere, Duncan. "Meteorologists track down elusive triple and quadruple rainbows." Wired. Oct. 6, 2011. (Dec. 16, 2014) http://www.wired.co.uk/news/archive/2011-10/06/evidence-triple-rainbows
- Mass, Cliff. "Triple rainbow." Cliff Mass Weather Blog. Nov. 25, 2012. (Dec. 16, 2014) http://cliffmass.blogspot.com/2012/11/triple-rainbow.html
- Mass, Cliff. "Why are there double rainbows?" Cliff Mass Weather Blog. April 22, 2014. (Dec. 16, 2014) http://cliffmass.blogspot.com/2014/04/why-are-there-double-rainbows.html
- Theusner, Michael. "Homepage of Michael Theusner." 2015. (Dec. 16, 2014) http://www.theusner.eu/about.html
- Theusner, Michael. "Photographic observation of a natural fourth-order rainbow." Applied Optics. 2011. (Dec. 16, 2014) http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-50-28-F129