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.
D. J. Hawkins says: August 6, 2012 at 6:28 pm
It may well be “nulli novus sub sollis”, but there is no date on the article. It could have been yesterday.
No date, but the web page was last updated 2 Aug 2009, which kind of seems like prior art.
I covered this months ago:
http://www.paneuropeannetworks.com/detail/news/computer-scientists-unweave-a-rainbow-.html
wonderful…now all we need is a photo and explanation for the green flash
rare? we get about 10-15 a year where I live
Obviously ‘Mickey Mouse’ research – if he wants to make his name he should have worked AGW in.
Clearly, due to global warming, we will be seeing less rainbows in future and, as a result, children will grow up with lower imagination and creativity. Understanding the fate of humanity thus requires much further work in the science of rainbows to try to minimize these tragic consequences of AGW before it is too late. QED!
Saw a triple rainbow in Ireland, way way back … summer 1970. Extraordinary.
Is Disney planning a new theme park? ROYGBIV World?
Or a chain of Burgeroid King drop-in restaurants as revenge on McDonalds for using Mickey Dee as an unofficial trademark?
“Burgeroids”? I thought it was raining meatballs.
nulli novus sub sollis? Nothing new under the Sun? Didn’t do Latin at skool, I had a no alternative education!
Ah, those wonderful, sophisticated computer models, with their simulations & representations, that brought us wierd & wonderful creatures in equally wierd & wonerful space craft from long time ago in a galaxy far far away, followed by dinosaurs walking upon the Earth once more, to the USS Enterprize warping it across the galaxy! Marvelous stuff, if it wasn’t so real you couldn’t have imagined it! I love the logical reasoning to all computer modelling, they input to the front end what they expect to get out the back end, then when they get out the back end what they input to the front end, they claim it as evidence of proof that their theory was right all along! ;-)) I have this theory that man can dodge a speeding bullet aimed directly at his head from close range, my computer model has proven it to be true, any climate scientist want to try it out for real……? No, I thought perhaps not!
The wonders of light and physics described by Walter Lewin, professor of physics at the Massachusetts Institute of Technology. How to make a rainbow with a sprinkler starts at about 39 minutes.
“From Disney Research (who knew?)”
My thoughts, entirely.
We will probably wake up one day and find that Disney has some outrageous copyright on rainbows. No more unauthorized representations of rainbows in movies, cartoons, art galleries, school-play productions, or childrens books…
What is the explanation for the sky between the primary and secondary rainbows of a double rainbow being darker than the rest of the sky?
Growing up and spending a lot of time in showery Scotland, I saw loads of rainbows and double rainbows. I never got as excited as the guy in Follow the Money’s video though. I’ve never seen a split rainbow.
gopal panicker says:
I’ve seen quite a few green flashes. I spend a lot of time working offshore and have recently been working offshore Mozambique and see a green flash most sunsets when the horizon is clear. I’ve even seen the occasional blue flash. I have also seen the green flash from onshore locartions in Oman and Sharjah where the sun sets over sand dunes.
To me the explanation is simple: it’s a prismatic effect.
Wikipedia has more…
http://en.wikipedia.org/wiki/Green_flash
I’ll try and take a movie of the green flash when I go back offshore Mozambique again later in the month and I’ll post it in Tips & Notes.
I like the fact they actually looked for a physical cause. Now how do we go about seeing if these burgeroids exist in real life. I envision a large water collider with millions of sensors, imagine the grant money!…ok, I may have gotten a little carried away with that last bit.
However I could see a droplet producer with maybe a vertical wind tunnel and a high speed camera. Produce droplets of various mass and film them as they fall against a terminal velocity wind. Should be rather simple to confirm this physical aspect of the model.
For those few here who may not have noticed, please note that the uppermost of the two rainbows has the spectrum of colors, reversed.
R.I.P Sir Bernard.
http://www.bbc.co.uk/news/uk-england-19164236
Very interesting topic.
But I’m not fully convinced that the simulation correctly depicts the phenomenon. A quick image search for “twinned rainbow” does not deliver one real life example of a split rainbow that looks like the computer simulation from Disney Research. Most photographs have the twinning near the top of the rainbow not at the side. On one site they even say: “…the twinning can only be seen for a short time and exclusively in the upper part of the rainbow.”
I saw half a rainbow yesterday and its end was in a wind farm. That’s where the gold is!
Crowds of people have looked for a physical cause and mostly gave up or were satisfied with comfortably-looking nonsense. If you enjoy careful thinking interspersed with much confusion and occasional sparks of enlightenment, it was for you that Miles Mathis wrote this essay: http://milesmathis.com/rainbow.html
That is free enterprise at its best developing and selling a product people want to buy and improving the product through work. And Disney has a purpose to use what they now know.
Paul Westhaver says:
August 6, 2012 at 6:58 pm
I’d love to see a double twinned complete circle bow.
Paul, I have seen many from a helicopter (mining exploration). Fantastic. You can see the shadow of the helicopter, of course, right in the centre of the circles.
Who needs oblate spheroids when you can have burgeroids? Are prolate spheroids now called footballoids?
Look like models all the way through – much like the rest of climate science. Tweaking a computer model is no substitute for a good falsifiable theory based on solid observational data.
It strikes me that if something as simple as rainbow,or even the shape of raindrops, isn’t understood then the likelihood that something as complex as the climate is understood is very low.
So they learned Modelling 101. Engineers and geoscientists know this all too well and come up against these situation all the time.
Our assumption that we are dealing with a homogeneous isotropic medium is an overly simplistic assumption.
Add anisotropy and inhomogeneity and welcome to the real world!