From Disney Research (who knew?)
Researchers unlock secret of the rare ‘twinned rainbow’
ZURICH — Scientists have yet to fully unravel the mysteries of rainbows, but a group of researchers from Disney Research, Zürich, UC San Diego, Universidad de Zaragoza, and Horley, UK, have used simulations of these natural wonders to unlock the secret to a rare optical phenomenon known as the twinned rainbow.
Unlike the more common double-rainbow, which consists of two separate and concentric rainbow arcs, the elusive twinned rainbow appears as two rainbows arcs that split from a single base rainbow. Sometimes it is even observed in combination with a double rainbow.
It is well-known that rainbows are caused by the interaction of sunlight with small water drops in the atmosphere; however, even though the study of rainbows can be traced back more than 2,000 years to the days of Aristotle, their complete and often complex behavior has not been fully understood until now.
“Everyone has seen rainbows, even double-rainbows, and they continue to fascinate the scientific community,” said Dr. Wojciech Jarosz, co-author of the paper and Research Scientist at Disney Research, Zürich. “Sometimes, when the conditions are just right, we can observe extremely exotic rainbows, such as a twinned rainbow. Until now, no one has really known why such rainbows occur.”
Jarosz and the international team of researchers studied virtual rainbows in simulation, considering the physical shape of water drops, and their complex interactions with both the particle and wave-nature of light. The key to the twinned rainbow mystery, Jarosz said, is the combination of different sizes of water drops falling from the sky.
“Previous simulations have assumed that raindrops are spherical. While this can easily explain the rainbow and even the double rainbow, it cannot explain the twinned rainbow,” he said. Real raindrops flatten as they fall, due to air resistance, and this flattening is more prominent in larger water drops. Such large drops end up resembling the shape of hamburgers, and are therefore called “burgeroids”.
“Sometimes two rain showers combine,” Jarosz said. “When the two are composed of different sized raindrops, each set of raindrops produces slightly deformed rainbows, which combine to form the elusive twinned rainbow.” The team developed software able to reproduce these conditions in simulation and the results matched, for the first time, twinned rainbows seen in photographs. The team also simulated a vast array of other rainbows matching photographs.
The team’s discovery was unintentional. “Initially the goal was to better depict rainbows for animated movies and video games and we thought rainbows were pretty well understood,” said Jarosz. “Along the way we discovered that science and current simulation methods simply could not explain some types of rainbows. This mystery really fueled our investigations.” The researchers now see potentially wider application of their method beyond computer graphics, speculating that, some day, accurate rendering models of atmospheric phenomena, like the one they developed, could have impact in areas such as meteorology for deducing the size of water drops from videos or photographs.
The research findings by will be presented Aug. 8 in the “Physics and Mathematics for Light” session at SIGGRAPH 2012, the International Conference on Computer Graphics and Interactive Techniques at the Los Angeles Convention Center. For a copy of the research paper, please visit the project web site at http://zurich.disneyresearch.com/~wjarosz/publications/sadeghi11physically.html.
About Disney Research
Disney Research is a network of research laboratories supporting The Walt Disney Company. Its purpose is to pursue scientific and technological innovation to advance the company’s broad media and entertainment efforts. Disney Research is managed by an internal Disney Research Council co-chaired by Disney-Pixar’s Ed Catmull and Walt Disney Imagineering’s Bruce Vaughn, and including the directors of the individual labs. It has facilities in Los Angeles, San Francisco, Pittsburgh, Boston and Zurich. Research topics include computer graphics, video processing, computer vision, robotics, radio and antennas, wireless communications, human-computer interaction, displays, data mining, machine learning and behavioral sciences.
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Wow… from videogames and the like cometh real science.
Sadly these findings would seem to rule out Unicorn flatulence as a source of rainbows, double or otherwise. It would appear that wind / subsidy farms will still require fossil fuel backup in spinning standby.
Funny, the folks at Atmospheric Optics noted something like this in their article on twinned rainbows:
http://www.atoptics.co.uk/rainbows/twin1.htm
“A stronger possibility is that non-spherical raindrops produce one or both bows. Surface tension forces keep small raindrops fiercely spherical but as they fall large drops are flattened by air resistance or might even oscillate between flattened and elongated spheroids.”
Disney Research in Zurich?
How beautiful! I didn’t know about split rainbows. Interesting findings that makes sense. Thank you for covering this. 🙂
I once saw a triple Rainbow, conditions were perfect. Right at sunset over the Pacific having just experienced torrential rains which were powerful enough to wash cars down the hill near our condo in Del Mar, CA, circa 1979.
It may well be “nulli novus sub sollis”, but there is no date on the article. It could have been yesterday.
Can I get those burgeroids with fries?
I’d love to see a double twinned complete circle bow.
Lovely article. Thanks Anthony.
These are super-duper scientist types figuring out the rainbow. Sorry, Isaac N got there first.
Data mining and rainbows? Who knew?!
Aside from that, it’s fascinating!
In the Caribbean I once saw a night rainbow, created by light from a full moon over the sea, after a late evening shower. (Not the familiar cold-weather halo around the moon; this was the arc, only the colors were very pale and–IIRC—not all were visible.)
Interesting stuff.
I always thought it was the directional velocity of multiple different squall lines (if you will) within the same storms varied/viewable reflective rain patterns.
Question?
We often see boasting from varied manufacturers of different visual products that have specific viewing angles. What is the viewing angle of a rainbow?
I really want to know and don’t 🙂
If you don’t like “super-duper scientist types,” you may prefer a slacker version:
So, they found some parameters they can set in a computer simulation that appear to match observations, and from that, they conclude that the simulation parameters are correct.
In this case, I suspect that they may have hit the nail on the head. But until they produce evidence that corroborates their assumptions without the use of computer simulations, they no more have proof that their theory is correct than do the climate scientists who produce computer simulations that seem to reproduce observations, but fall apart as time goes on.
The researchers now see potentially wider application of their method beyond computer graphics, speculating that, some day, accurate rendering models of atmospheric phenomena, like the one they developed, could have impact in areas such as meteorology for deducing the size of water drops from videos or photographs.
I was bracing myself for a claim their research could improve climate models. But then I realized that Disney participating in the development of climate models would be nixed by the climate PR department.
@ur momisugly Follow the Money
Whoa man, that was like soooo awesome dude.
(If you didn’t post it I would have!)
Followthemoney-
How id the double rainbow slacker vid not make the original post?
with autotune
“What does it mean?”
[email invalid. see site policy ~ctm]
It changes to get real science for once in contrast to the Mickey Mouse science of the warmists.
I guess there is a CROCK of something at the end of these rainbows too
There is no way to say this without appearing flippant so I’ll just state that it’s not intended to be. As a photographer I kinda thought that this was common knowledge.
Great story anyway 🙂
So… When I’m sneakily playing a video game…. I can honestly say that I’m researching science….:-)
But jokes aside… There ya go. The phenomenon is now explained…. reasonably equal amounts of two different sizes of water droplets and their effect on the light passing through them.
…. and everytime I eat a hamburger….. I’ll think of Rainbows….. Thank you science. 🙂